WeCreativez WhatsApp Support
Welcome! My name is Damaris I am online and ready to help you via WhatsApp chat. Let me know if you need my assistance.

Download this complete Project material titled; Species Composition And Genetic Structures Of Glossina Populations In Selected Nigerian National Parks with abstract, chapters 1-5, references, and questionnaire. Preview Abstract or chapter one below

  • Format: PDF and MS Word (DOC)
  • pages = 65

 3,000

ABSTRACT

A study of population genetic structure of tsetse flies (Glossina spp), vectors of Human and Animal trypanosomiasis, was undertaken in order to increase our understanding on the distribution and dynamics of tsetse fly populations in Nigeria. Tsetse flies were collected in selected four Nigeria National Parks/Game Reserve namely, Kainji Lake National Park, Old Oyo National Park, Cross River National Park, Yankari Game Reserve and a highly tsetse infested agropastoral area within the Federal Capital Territory Abuja at ijah Gwari, and examined using Cytochrome Oxidase C SU1 (CO 1), Internal transcribed spacer-1(ITS-1) sequences and geometric wing morphometrics. Flies were sampled using standard biconical traps, while ambient temperature and relative humidity conditions were recorded with a whirling hygrometer and co-ordinates of sampled locations and trapping points were recorded with GPS device for geo-referencing. A total of 1891 tsetse flies were collected comprising, Glossina tachinoides (1050, 55.53%), Glossina palpalis palpalis (568, 30.04%), Glossina morsitans submorsitans (270, 14.23%) and Glossina fusca (3, 0.16%). Analysed data showed significant difference (χ2 (4) = 1375.417, p ˂ 0.001) in the relative abundance of Glossina spp. per sampled location, whereas pairwise comparison showed no significant difference (p = 1.000) in the relative abundance of Glossina spp. between Cross River and Ijah Gwari sampled locations. Apparent densities of Glossina populations were significantly different (χ2 (4) = 20.500, p < 0.001) per sampled location. Pairwise comparison however, showed that Old Oyo, Yankari, and Kainji locations had comparatively high apparent densities of Glossina spp.
Male and female fly ratios were significantly different (χ2 (1) = 4.000, p =0.046) with higher proportion of male flies caught than females in some but not all species in all regions sampled. The composition of Glossina species in the sampled locations showed no significant association (χ2 (12) = 2134.106, p > 0.001), as well as no significant difference (t = -1.580, p 0.133 > α = 0.05)
viii
in tsetse catches in relation to ambient temperature and relative humidity conditions was observed in Yankari Game Reserve. Significant difference (t = -10.633, p =0.000 ˂ α =0.05) in tsetse catches in relation to ambient temperature and relative humidity conditions was observed in Kainji Lake National Park, (t = -36.290, p = 0.000 ˂ α = 0.05) in Old Oyo National Park, (t = -18.939, p = 0.000 ˂ α = 0.05) in Cross River National Park and (t = -4.613, p = 0.01 ˂ α = 0.05) in Ijah Gwari. No significant correlations between tsetse catches and ambient temperature and relative humidity conditions were observed in most of the trapping locations visited, suggesting that the distribution of flies across the sampled locations were probably influenced by other environmental factors than climatic conditions alone.
Tenerity phenomenon showed significant difference (χ2 (4) = 20.500, p < 0.001) in the proportion of teneral and non teneral flies amongst the four Glossina species caught, with the proportion of teneral flies in each Glossina species being significantly higher than the non-teneral flies, except in G. fusca in which there was no significant difference between the number of teneral and non-teneral flies caught. Pairwise comparison showed that Yankari Game Reserve, Old Oyo and Kainji Lake National Parks had comparable tenerity of Glossina species.
Five Glossina spp. for which no information on their COI sequences is available on the Genbank, could not be identified molecularly using phylogenetic analysis. However, the study demonstrated the splitting of G. p. palpalis populations into two major groups, a West African Clade (WAC) and a Central Africa Clade (CAC), with the convergence zone of the two major groups (WAC and CAC) found co-existing sypatrically in the region of Cross River National Park at the Nigerian-Cameroonian border area. While the ITS-1 regions of the G. p. palpalis subpopulations did not show any differences, the geometric wing morphometrics showed a sex dependent shape dimorphism in 41 flies examined from Dodeo region in Cameroon.
ix
Since the COI sequences have clearly revealed the splitting of Glossina palpalis palpalis populations into two major groups, the question requiring answer is whether the two groups of G. p. palpalis identified in this study can interbreed and if so are the vectorial capacities of the two groups of flies the same, these need to be investigated. This is even so as the isolation status of flies in the National Parks need to be investigated especially as migration of other flies into cleared areas may hinder the success of tsetse control using SIT, whereas limited migration may lead to success.
It is concluded that information generated from this study, would aid the choice of effective anti-tsetse management approaches in the country’s National Parks using a component of the sterile insect technique (SIT) as being advocated by the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC).A study of population genetic structure of tsetse flies (Glossina spp), vectors of Human and Animal trypanosomiasis, was undertaken in order to increase our understanding on the distribution and dynamics of tsetse fly populations in Nigeria. Tsetse flies were collected in selected four Nigeria National Parks/Game Reserve namely, Kainji Lake National Park, Old Oyo National Park, Cross River National Park, Yankari Game Reserve and a highly tsetse infested agropastoral area within the Federal Capital Territory Abuja at ijah Gwari, and examined using Cytochrome Oxidase C SU1 (CO 1), Internal transcribed spacer-1(ITS-1) sequences and geometric wing morphometrics. Flies were sampled using standard biconical traps, while ambient temperature and relative humidity conditions were recorded with a whirling hygrometer and co-ordinates of sampled locations and trapping points were recorded with GPS device for geo-referencing. A total of 1891 tsetse flies were collected comprising, Glossina tachinoides (1050, 55.53%), Glossina palpalis palpalis (568, 30.04%), Glossina morsitans submorsitans (270, 14.23%) and Glossina fusca (3, 0.16%). Analysed data showed significant difference (χ2 (4) = 1375.417, p ˂ 0.001) in the relative abundance of Glossina spp. per sampled location, whereas pairwise comparison showed no significant difference (p = 1.000) in the relative abundance of Glossina spp. between Cross River and Ijah Gwari sampled locations. Apparent densities of Glossina populations were significantly different (χ2 (4) = 20.500, p < 0.001) per sampled location. Pairwise comparison however, showed that Old Oyo, Yankari, and Kainji locations had comparatively high apparent densities of Glossina spp.
Male and female fly ratios were significantly different (χ2 (1) = 4.000, p =0.046) with higher proportion of male flies caught than females in some but not all species in all regions sampled. The composition of Glossina species in the sampled locations showed no significant association (χ2 (12) = 2134.106, p > 0.001), as well as no significant difference (t = -1.580, p 0.133 > α = 0.05)
viii
in tsetse catches in relation to ambient temperature and relative humidity conditions was observed in Yankari Game Reserve. Significant difference (t = -10.633, p =0.000 ˂ α =0.05) in tsetse catches in relation to ambient temperature and relative humidity conditions was observed in Kainji Lake National Park, (t = -36.290, p = 0.000 ˂ α = 0.05) in Old Oyo National Park, (t = -18.939, p = 0.000 ˂ α = 0.05) in Cross River National Park and (t = -4.613, p = 0.01 ˂ α = 0.05) in Ijah Gwari. No significant correlations between tsetse catches and ambient temperature and relative humidity conditions were observed in most of the trapping locations visited, suggesting that the distribution of flies across the sampled locations were probably influenced by other environmental factors than climatic conditions alone.
Tenerity phenomenon showed significant difference (χ2 (4) = 20.500, p < 0.001) in the proportion of teneral and non teneral flies amongst the four Glossina species caught, with the proportion of teneral flies in each Glossina species being significantly higher than the non-teneral flies, except in G. fusca in which there was no significant difference between the number of teneral and non-teneral flies caught. Pairwise comparison showed that Yankari Game Reserve, Old Oyo and Kainji Lake National Parks had comparable tenerity of Glossina species.
Five Glossina spp. for which no information on their COI sequences is available on the Genbank, could not be identified molecularly using phylogenetic analysis. However, the study demonstrated the splitting of G. p. palpalis populations into two major groups, a West African Clade (WAC) and a Central Africa Clade (CAC), with the convergence zone of the two major groups (WAC and CAC) found co-existing sypatrically in the region of Cross River National Park at the Nigerian-Cameroonian border area. While the ITS-1 regions of the G. p. palpalis subpopulations did not show any differences, the geometric wing morphometrics showed a sex dependent shape dimorphism in 41 flies examined from Dodeo region in Cameroon.
ix
Since the COI sequences have clearly revealed the splitting of Glossina palpalis palpalis populations into two major groups, the question requiring answer is whether the two groups of G. p. palpalis identified in this study can interbreed and if so are the vectorial capacities of the two groups of flies the same, these need to be investigated. This is even so as the isolation status of flies in the National Parks need to be investigated especially as migration of other flies into cleared areas may hinder the success of tsetse control using SIT, whereas limited migration may lead to success.
It is concluded that information generated from this study, would aid the choice of effective anti-tsetse management approaches in the country’s National Parks using a component of the sterile insect technique (SIT) as being advocated by the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC).

 

 

TABLE OF CONTENTS

Content Page
TITLE PAGE ………………………………………………………………………………………………………………………………. i
DECLARATION ………………………………………………………………………………………………………………………… ii
CERTIFICATION ……………………………………………………………………………………………………………………… iii
AKNOWLEDGEMENTS ……………………………………………………………………………………………………………. iv
DEDICATION …………………………………………………………………………………………………………………………… vi
ABSTRACT ……………………………………………………………………………………………………………………………… vii
TABLE OF CONTENTS ……………………………………………………………………………………………………………… x
LIST OF TABLES …………………………………………………………………………………………………………………….. xx
LIST OF FIGURES ………………………………………………………………………………………………………………….. xxi
LIST OF PLATES ………………………………………………………………………………………………………………….. xxvi
LIST OF APPENDICES …………………………………………………………………………………………………………. xxvii
LIST OF ABREVIATIONS/ACRONYMS ………………………………………………………………………………… xxix
CHAPTER ONE ……………………………………………………………………………………………………………………….. 1
1.0 INTRODUCTION…………………………………………………………………………………………………… 1
1.1 Preamble ………………………………………………………………………………………………………………… 1
1.2 Statement of the Research Problem …………………………………………………………………………. 7
1.3 Justification ……………………………………………………………………………………………………………. 7
1.4 Aim and Objectives …………………………………………………………………………………………………. 8
xi
1.4.1 Aim ……………………………………………………………………………………………………………………… 8
1.4.2 Objectives …………………………………………………………………………………………………………….. 8
1.5 Research Questions …………………………………………………………………………………………………. 8
CHAPTER TWO …………………………………………………………………………………………………………………….. 10
2.0 LITERATURE REVIEW ……………………………………………………………………………………… 10
2.1 Economic Importance of Trypanosomiasis …………………………………………………………….. 10
2.2 The Causative Agent – Trypanosoma species …………………………………………………………… 13
2.2.1 Description of trypanosome …………………………………………………………………………………… 13
2.2.2 Classification of trypanosomes ………………………………………………………………………………. 15
2.2.3 Life cycle of trypanosomes and disease distribution …………………………………………………. 15
2.2.3.1 Life cycle of trypanosomes ………………………………………………………………………………….. 15
2.2.3.2 Disease distribution …………………………………………………………………………………………… 18
2.2.4 Historical trends …………………………………………………………………………………………………… 21
2.3 Trypanosome –Tsetse Interaction ………………………………………………………………………….. 25
2.4 Evasion of Host Immune System by Trypanosomes ………………………………………………… 26
2.4.1 Variant Surface Glycoprotein (VSG) ………………………………………………………………………. 26
2.4.2 Anti-pathogenicity inducing “host” factors ……………………………………………………………… 26
2.5 Tsetse Flies ……………………………………………………………………………………………………………. 27
2.6 Male and Female Flies Differentiation ……………………………………………………………………. 30
2.7 Glossina Identification …………………………………………………………………………………………… 32
2.8 Tsetse Life History and Biology ……………………………………………………………………………… 34
2.8.1 Mating ………………………………………………………………………………………………………………… 34
2.8.2 Ovulation…………………………………………………………………………………………………………….. 34
2.8.3 Egg stage …………………………………………………………………………………………………………….. 34
2.8.4 Larval and pupal stages …………………………………………………………………………………………. 36
xii
2.8.5 Adult Emergence …………………………………………………………………………………………………. 36
2.9 Teneral and Non-Teneral Flies ………………………………………………………………………………. 37
2.10 Age Determination in Male and Female Flies ……………………………………………………….. 37
2.10.1 Wing fray analysis in males …………………………………………………………………………………. 37
2.10.2 Ovarian configuration in female flies ……………………………………………………………………. 41
2.11 Physiological States in Female Flies ……………………………………………………………………… 43
2.12 Hunger Staging……………………………………………………………………………………………………. 43
2.13 Tsetse Ecology …………………………………………………………………………………………………….. 44
2.14 Survival and Longevity of Tsetse Flies………………………………………………………………….. 45
2.15 Activity Cycle ……………………………………………………………………………………………………… 45
2.16 Feeding Behaviour and Host Selection …………………………………………………………………. 46
2.17 Host Detection …………………………………………………………………………………………………….. 47
2.18 Resting Behaviour ……………………………………………………………………………………………….. 48
2.19 Classification of Tsetse Flies ………………………………………………………………………………… 49
2.20 Distinctive Characteristics …………………………………………………………………………………… 50
2.20.1 G. palpalis group ……………………………………………………………………………………………….. 50
2.20.1.1 G. tachinoides …………………………………………………………………………………………………. 51
2.20.1.2 G. palpalis and G. fuscipes ……………………………………………………………………………….. 51
2.20.1.3 G. pallicera and G. caliginea …………………………………………………………………………….. 51
2.20.2 G. morsitans group……………………………………………………………………………………………… 51
2.20.3 G. fusca group ……………………………………………………………………………………………………. 52
2.21 Tsetse Fly Distribution and Abundance ……………………………………………………………….. 53
2.21.1 Historical trends …………………………………………………………………………………………………. 53
2.21.2 Speciation in tsetse flies ………………………………………………………………………………………. 53
2.21.3 Phylogeny of Glossina ………………………………………………………………………………………… 54
xiii
2.21.4 Glossina distribution …………………………………………………………………………………………… 55
2.21.5 Tsetse distribution in Nigeria ……………………………………………………………………………….. 59
2.21.6 Tsetse flies in Nigeria National Parks and Game Reserves ………………………………………. 64
2.22 Dispersal in Tsetse Flies……………………………………………………………………………………….. 68
2.23 Disease Transmission …………………………………………………………………………………………… 70
2.23.1 Cyclic transmission …………………………………………………………………………………………….. 70
2.23.2 Non-cyclic transmission (Mechanical transmission) ……………………………………………….. 73
2.24 Vectorial Capacity and Transmission Potential…………………………………………………….. 74
2.25 Infection Rates in Tsetse ………………………………………………………………………………………. 74
2.26 Tsetse Immunity ………………………………………………………………………………………………….. 76
2.27 Tsetse Sampling …………………………………………………………………………………………………… 78
2.27.1 Fly rounds …………………………………………………………………………………………………………. 79
2.27.2 Traps ………………………………………………………………………………………………………………… 80
2.27.3 Electric nets ……………………………………………………………………………………………………….. 81
2.27.4 Visual and olfactory attractants of tsetse flies ………………………………………………………… 81
2.27.5 Screens, targets and traps …………………………………………………………………………………….. 81
2.27.6 Odour attractants ………………………………………………………………………………………………… 82
2.28 Population Dynamics …………………………………………………………………………………………… 83
2.29 Population Analysis …………………………………………………………………………………………….. 84
2.30 Genetic Variation in Tsetse Flies ………………………………………………………………………….. 85
2.30.1 Laboratory studies ………………………………………………………………………………………………. 85
2.30.2 Variation in natural populations……………………………………………………………………………. 86
2.31 Genetic Markers in Tsetse Flies……………………………………………………………………………. 87
2.32 Biochemical / Protein Markers …………………………………………………………………………….. 87
2.32.1 Allozymes …………………………………………………………………………………………………………. 87
xiv
2.33 Molecular / DNA Markers …………………………………………………………………………………… 88
2.33.1 Microsatellites ……………………………………………………………………………………………………. 88
2.33.2 Mitochondrial DNA (mtDNA) …………………………………………………………………………….. 89
2.34 Geometry Wing Morphometrics ………………………………………………………………………….. 90
2.35 Tsetse and Trypanosomiasis Control ……………………………………………………………………. 91
2.35.1 Control of trypanosomiasis using Chemotherapy and Chemoprophylaxis ………………….. 91
2.35.2 Use of trypanosome resistant (Trypanotolerant) breeds …………………………………………… 93
2.36 Tsetse Control……………………………………………………………………………………………………… 93
2.36.1 Direct destruction of tsetse flies ……………………………………………………………………………. 94
2.36.2 Tsetse control by game elimination ………………………………………………………………………. 94
2.36.3 Tsetse fly control by bush clearing ……………………………………………………………………….. 95
2.36.4 Tsetse control by population resettlement ……………………………………………………………… 96
2.36.5 Tsetse control by aerial spraying of insecticides …………………………………………………….. 97
2.36.6 Tsetse control by ground spraying of insecticides …………………………………………………… 98
2.36.7 Trapping ……………………………………………………………………………………………………………. 99
2.36.8 Insecticide treated traps and targets …………………………………………………………………….. 100
2.36.9 Pour-on formulations ………………………………………………………………………………………… 102
2.37 Biological control of tsetse ………………………………………………………………………………….. 103
2.37.1 Predators …………………………………………………………………………………………………………. 103
2.37.2 Parasites ………………………………………………………………………………………………………….. 103
2.37.3 Parasitoids ……………………………………………………………………………………………………….. 103
2.37.4 Pathogens ………………………………………………………………………………………………………… 104
2.38 Genetic Control of Tsetse Flies …………………………………………………………………………… 104
2.38.1 Transgenesis …………………………………………………………………………………………………….. 104
2.38.2 Sterile Insect Technique (SIT) ……………………………………………………………………………. 105
xv
2.38.3 The Sterile Insect Technique via chemical sterilisation: ………………………………………… 107
2.39 Benefits of Tsetse and Trypanosomiasis Control …………………………………………………. 108
2.40 Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) ………. 108
2.41 Criteria for Tsetse Control Using SIT ………………………………………………………………… 109
CHAPTER THREE ……………………………………………………………………………………………………………….. 110
3.0 MATERIALS AND METHODS ……………………………………………………………………….. 110
3.1 Description of Study Areas ………………………………………………………………………………….. 110
3.1.1 Yankari Game Reserve ……………………………………………………………………………………….. 110
3.1.2 Kainji Lake National Park …………………………………………………………………………………… 113
3.1.3 Old Oyo National Park………………………………………………………………………………………… 115
3.1.4 Cross River National Park …………………………………………………………………………………… 115
3.1.5 Ijah Gwari …………………………………………………………………………………………………………. 118
3.2 Entry Permit into National Parks ………………………………………………………………………… 118
3.3 Methodology ……………………………………………………………………………………………………….. 120
3.3.1 Sample collection, handling and documentation: ……………………………………………………. 120
3.3.2 Mapping of Glossina species distribution using the Global Positioning System (GPS) .. 120
3.3.3 Micro climatic conditions in National Parks ………………………………………………………….. 122
3.3.4 Species composition, relative abundance and distribution ……………………………………….. 122
3.3.5 Apparent density of Glossina species in sampled locations ……………………………………… 122
3.3.6 Sex ratio ……………………………………………………………………………………………………………. 122
3.3.7 Teneral and non-teneral flies ……………………………………………………………………………….. 123
3.3.8 Hunger staging …………………………………………………………………………………………………… 123
3.3.9 Collection and preservation of tsetse fly tissues for genetic analysis …………………………. 124
3.4 Molecular Studies………………………………………………………………………………………………… 124
3.4.1 DNA Extraction …………………………………………………………………………………………………. 124
xvi
3.4.2 DNA Quantification ……………………………………………………………………………………………. 125
3.4.3 Preparation of Master Mix …………………………………………………………………………………… 126
3.4.4 PCR Amplifications ……………………………………………………………………………………………. 126
3.4.5 Preparation of Agarose Gel ………………………………………………………………………………….. 126
3.4.6 Gel Electrophoresis …………………………………………………………………………………………….. 127
3.4.7 Purification of DNA samples for sequencing …………………………………………………………. 127
3.4.8 Sequensing reactions …………………………………………………………………………………………… 128
3.4.9 Sequencing ………………………………………………………………………………………………………… 128
3.5 Data Analyses ……………………………………………………………………………………………………… 128
3.5.1 Differential Statistics ………………………………………………………………………………………….. 128
3.6 Genetic Analyses …………………………………………………………………………………………………. 129
3.6.1 Sequence alignments …………………………………………………………………………………………… 129
3.6.2 Molecular species identification …………………………………………………………………………… 129
3.6.3 Haplotype diversity …………………………………………………………………………………………….. 130
3.6.4 Nucleotide diversity (Genetic variation) ………………………………………………………………… 130
3.6.5 Genetic differentiation (Average Evolutionary Divergence) …………………………………….. 131
3.6.6 Phylogenetic relationships …………………………………………………………………………………… 132
3.7 Geometric Wing Morphometrics………………………………………………………………………….. 132
CHAPTER FOUR ………………………………………………………………………………………………………………….. 134
4.0 RESULTS …………………………………………………………………………………………………………… 134
4.1 Ecological Studies………………………………………………………………………………………………… 134
4.1.1 Glossina species composition and relative abundance …………………………………………….. 134
4.1.2 Glossina spp. distribution in the National Parks and Ijah Gwari ……………………………….. 139
4.1.3 Glossina spp. distribution in relation to ambient temperature and relative humidity conditions …………………………………………………………………………………………………………….. 141
xvii
4.1.4 Apparent density of tsetse fly populations in the National Parks and Ijah Gwari ………… 159
4.1.5 Sex ratio ……………………………………………………………………………………………………………. 161
4.1.6 Teneral and non-teneral flies ……………………………………………………………………………….. 163
4.1.7 Hunger staging …………………………………………………………………………………………………… 163
4.2 Molecular Studies………………………………………………………………………………………………… 166
4.2.1 Amplifications……………………………………………………………………………………………………. 166
4.2.2 Molecular species identification …………………………………………………………………………… 166
4.2.3 Characteristics of CO1 sequences of Glossina spp. in sampled locations …………………… 171
4.2.4 Haplotype diversity …………………………………………………………………………………………….. 177
4.2.5 Nucleotide diversity (Genetic variations) ………………………………………………………………. 177
4.3 Genetic Differentiation (Average Evolutionary Divergence) in Sampled Glossina spp………………………………………………………………………………………………………………………. 187
4.3.1 G. m. submorsitans populations in Yankari Game Reserve ……………………………………… 187
4.3.2 G. m. submorsitans populations in Kainji Lake National Park………………………………….. 187
4.3.3 G. tachinoides populations in Yankari Game Reserve …………………………………………….. 187
4.3.4 G. tachinoides populations in Kainji Lake National Park ………………………………………… 192
4.3.5 G. p. palpalis populations in Old Oyo National Park ………………………………………………. 192
4.3.6 G. p. palpalis populations in Cross River National Park ………………………………………….. 192
4.3.7 G. p. palpalis populations in Ijah Gwari ………………………………………………………………… 192
4.4 Phylogenetic Relationships of Glossina Species in National Parks and Ijah Gwari …. 198
4.5 Phylogenetic Relationships with Particular Reference to G. p. palpalis Populations .. 198
4.6 ITS-1 Analysis …………………………………………………………………………………………………….. 201
4.7 Geometric Wing Morphometrics………………………………………………………………………….. 202
CHAPTER FIVE …………………………………………………………………………………………………………………… 206
5.0 DISCUSSION ……………………………………………………………………………………………………… 206
xviii
5.1 Ecological Studies………………………………………………………………………………………………… 206
5.1.1 Glossina species composition and relative abundance in National Parks and Ijah Gwari…………………………………………………………………………………………………………………… 206
5.1.2 Yankari Game Reserve ……………………………………………………………………………………….. 206
5.1.3 Kainji Lake National Park …………………………………………………………………………………… 209
5.1.4 Old Oyo National Park………………………………………………………………………………………… 210
5.1.5 Cross River National Park …………………………………………………………………………………… 212
5.1.6 Ijah Gwari …………………………………………………………………………………………………………. 213
5.1.7 Glossina spp. distribution in the National Parks and Ijah Gwari ……………………………….. 216
5.1.8 Glossina spp. distribution in relation to ambient temperature and relative humidity conditions. ……………………………………………………………………………………………………………. 217
5.2 Apparent Density of Tsetse Fly Populations in the National Parks and Ijah Gwari … 222
5.3 Sex Ratio …………………………………………………………………………………………………………….. 227
5.4 Teneral and Non-Teneral Flies …………………………………………………………………………….. 230
5.5 Hunger Staging……………………………………………………………………………………………………. 230
5.6 Molecular Studies………………………………………………………………………………………………… 231
5.6.1 Amplifications……………………………………………………………………………………………………. 231
5.6.2 Molecular species identification …………………………………………………………………………… 231
5.6.3 Characteristics of CO1 sequences of Glossina spp. in sampled locations …………………… 232
5.6.4 Haplotype diversity (Genetic variability) ………………………………………………………………. 233
5.6.5 Nucleotide diversity (Genetic variation) ………………………………………………………………… 233
5.7 Genetic Differentiation in Glossina spp. in Sampled Locations ……………………………… 236
5.7.1 G. m. submorsitans populations in Yankari Game Reserve ……………………………………… 236
5.7.2 G. m. submorsitans populations in Kainji Lake National Park………………………………….. 237
5.7.3 G. tachinoides populations in Yankari Game Reserve …………………………………………….. 237
5.7.4 G. tachinoides populations in Kainji Lake National Park ………………………………………… 238
xix
5.7.5 G. p. palpalis populations in Old Oyo National Park ………………………………………………. 238
5.7.6 G. p. palpalis populations in Cross River National Park ………………………………………….. 238
5.7.7 G. p. palpalis populations in Ijah Gwari ………………………………………………………………… 239
5.8 Phylogenetic Relationships of Glossina species in National Parks and Ijah Gwari ….. 241
5.9 Phylogenetic Relationships with Particular Reference to Glossina palpalis palpalis Populations. ………………………………………………………………………………………………………… 244
5.10 Internal Transcribed Spacer (ITS)-1 Analysis …………………………………………………….. 250
5.11 Geometric Wing Morphometrics………………………………………………………………………… 250
CHAPTER SIX ……………………………………………………………………………………………………………………… 252
6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS ………………………………………. 252
6.1 Summary …………………………………………………………………………………………………………….. 252
6.2 Conclusion ………………………………………………………………………………………………………….. 255
6.3 Recommendations ……………………………………………………………………………………………….. 256
REFERENCES ………………………………………………………………………………………………………………………. 257
APPENDICES ……………………………………………………………………………………………………………………….. 297Content Page
TITLE PAGE ………………………………………………………………………………………………………………………………. i
DECLARATION ………………………………………………………………………………………………………………………… ii
CERTIFICATION ……………………………………………………………………………………………………………………… iii
AKNOWLEDGEMENTS ……………………………………………………………………………………………………………. iv
DEDICATION …………………………………………………………………………………………………………………………… vi
ABSTRACT ……………………………………………………………………………………………………………………………… vii
TABLE OF CONTENTS ……………………………………………………………………………………………………………… x
LIST OF TABLES …………………………………………………………………………………………………………………….. xx
LIST OF FIGURES ………………………………………………………………………………………………………………….. xxi
LIST OF PLATES ………………………………………………………………………………………………………………….. xxvi
LIST OF APPENDICES …………………………………………………………………………………………………………. xxvii
LIST OF ABREVIATIONS/ACRONYMS ………………………………………………………………………………… xxix
CHAPTER ONE ……………………………………………………………………………………………………………………….. 1
1.0 INTRODUCTION…………………………………………………………………………………………………… 1
1.1 Preamble ………………………………………………………………………………………………………………… 1
1.2 Statement of the Research Problem …………………………………………………………………………. 7
1.3 Justification ……………………………………………………………………………………………………………. 7
1.4 Aim and Objectives …………………………………………………………………………………………………. 8
xi
1.4.1 Aim ……………………………………………………………………………………………………………………… 8
1.4.2 Objectives …………………………………………………………………………………………………………….. 8
1.5 Research Questions …………………………………………………………………………………………………. 8
CHAPTER TWO …………………………………………………………………………………………………………………….. 10
2.0 LITERATURE REVIEW ……………………………………………………………………………………… 10
2.1 Economic Importance of Trypanosomiasis …………………………………………………………….. 10
2.2 The Causative Agent – Trypanosoma species …………………………………………………………… 13
2.2.1 Description of trypanosome …………………………………………………………………………………… 13
2.2.2 Classification of trypanosomes ………………………………………………………………………………. 15
2.2.3 Life cycle of trypanosomes and disease distribution …………………………………………………. 15
2.2.3.1 Life cycle of trypanosomes ………………………………………………………………………………….. 15
2.2.3.2 Disease distribution …………………………………………………………………………………………… 18
2.2.4 Historical trends …………………………………………………………………………………………………… 21
2.3 Trypanosome –Tsetse Interaction ………………………………………………………………………….. 25
2.4 Evasion of Host Immune System by Trypanosomes ………………………………………………… 26
2.4.1 Variant Surface Glycoprotein (VSG) ………………………………………………………………………. 26
2.4.2 Anti-pathogenicity inducing “host” factors ……………………………………………………………… 26
2.5 Tsetse Flies ……………………………………………………………………………………………………………. 27
2.6 Male and Female Flies Differentiation ……………………………………………………………………. 30
2.7 Glossina Identification …………………………………………………………………………………………… 32
2.8 Tsetse Life History and Biology ……………………………………………………………………………… 34
2.8.1 Mating ………………………………………………………………………………………………………………… 34
2.8.2 Ovulation…………………………………………………………………………………………………………….. 34
2.8.3 Egg stage …………………………………………………………………………………………………………….. 34
2.8.4 Larval and pupal stages …………………………………………………………………………………………. 36
xii
2.8.5 Adult Emergence …………………………………………………………………………………………………. 36
2.9 Teneral and Non-Teneral Flies ………………………………………………………………………………. 37
2.10 Age Determination in Male and Female Flies ……………………………………………………….. 37
2.10.1 Wing fray analysis in males …………………………………………………………………………………. 37
2.10.2 Ovarian configuration in female flies ……………………………………………………………………. 41
2.11 Physiological States in Female Flies ……………………………………………………………………… 43
2.12 Hunger Staging……………………………………………………………………………………………………. 43
2.13 Tsetse Ecology …………………………………………………………………………………………………….. 44
2.14 Survival and Longevity of Tsetse Flies………………………………………………………………….. 45
2.15 Activity Cycle ……………………………………………………………………………………………………… 45
2.16 Feeding Behaviour and Host Selection …………………………………………………………………. 46
2.17 Host Detection …………………………………………………………………………………………………….. 47
2.18 Resting Behaviour ……………………………………………………………………………………………….. 48
2.19 Classification of Tsetse Flies ………………………………………………………………………………… 49
2.20 Distinctive Characteristics …………………………………………………………………………………… 50
2.20.1 G. palpalis group ……………………………………………………………………………………………….. 50
2.20.1.1 G. tachinoides …………………………………………………………………………………………………. 51
2.20.1.2 G. palpalis and G. fuscipes ……………………………………………………………………………….. 51
2.20.1.3 G. pallicera and G. caliginea …………………………………………………………………………….. 51
2.20.2 G. morsitans group……………………………………………………………………………………………… 51
2.20.3 G. fusca group ……………………………………………………………………………………………………. 52
2.21 Tsetse Fly Distribution and Abundance ……………………………………………………………….. 53
2.21.1 Historical trends …………………………………………………………………………………………………. 53
2.21.2 Speciation in tsetse flies ………………………………………………………………………………………. 53
2.21.3 Phylogeny of Glossina ………………………………………………………………………………………… 54
xiii
2.21.4 Glossina distribution …………………………………………………………………………………………… 55
2.21.5 Tsetse distribution in Nigeria ……………………………………………………………………………….. 59
2.21.6 Tsetse flies in Nigeria National Parks and Game Reserves ………………………………………. 64
2.22 Dispersal in Tsetse Flies……………………………………………………………………………………….. 68
2.23 Disease Transmission …………………………………………………………………………………………… 70
2.23.1 Cyclic transmission …………………………………………………………………………………………….. 70
2.23.2 Non-cyclic transmission (Mechanical transmission) ……………………………………………….. 73
2.24 Vectorial Capacity and Transmission Potential…………………………………………………….. 74
2.25 Infection Rates in Tsetse ………………………………………………………………………………………. 74
2.26 Tsetse Immunity ………………………………………………………………………………………………….. 76
2.27 Tsetse Sampling …………………………………………………………………………………………………… 78
2.27.1 Fly rounds …………………………………………………………………………………………………………. 79
2.27.2 Traps ………………………………………………………………………………………………………………… 80
2.27.3 Electric nets ……………………………………………………………………………………………………….. 81
2.27.4 Visual and olfactory attractants of tsetse flies ………………………………………………………… 81
2.27.5 Screens, targets and traps …………………………………………………………………………………….. 81
2.27.6 Odour attractants ………………………………………………………………………………………………… 82
2.28 Population Dynamics …………………………………………………………………………………………… 83
2.29 Population Analysis …………………………………………………………………………………………….. 84
2.30 Genetic Variation in Tsetse Flies ………………………………………………………………………….. 85
2.30.1 Laboratory studies ………………………………………………………………………………………………. 85
2.30.2 Variation in natural populations……………………………………………………………………………. 86
2.31 Genetic Markers in Tsetse Flies……………………………………………………………………………. 87
2.32 Biochemical / Protein Markers …………………………………………………………………………….. 87
2.32.1 Allozymes …………………………………………………………………………………………………………. 87
xiv
2.33 Molecular / DNA Markers …………………………………………………………………………………… 88
2.33.1 Microsatellites ……………………………………………………………………………………………………. 88
2.33.2 Mitochondrial DNA (mtDNA) …………………………………………………………………………….. 89
2.34 Geometry Wing Morphometrics ………………………………………………………………………….. 90
2.35 Tsetse and Trypanosomiasis Control ……………………………………………………………………. 91
2.35.1 Control of trypanosomiasis using Chemotherapy and Chemoprophylaxis ………………….. 91
2.35.2 Use of trypanosome resistant (Trypanotolerant) breeds …………………………………………… 93
2.36 Tsetse Control……………………………………………………………………………………………………… 93
2.36.1 Direct destruction of tsetse flies ……………………………………………………………………………. 94
2.36.2 Tsetse control by game elimination ………………………………………………………………………. 94
2.36.3 Tsetse fly control by bush clearing ……………………………………………………………………….. 95
2.36.4 Tsetse control by population resettlement ……………………………………………………………… 96
2.36.5 Tsetse control by aerial spraying of insecticides …………………………………………………….. 97
2.36.6 Tsetse control by ground spraying of insecticides …………………………………………………… 98
2.36.7 Trapping ……………………………………………………………………………………………………………. 99
2.36.8 Insecticide treated traps and targets …………………………………………………………………….. 100
2.36.9 Pour-on formulations ………………………………………………………………………………………… 102
2.37 Biological control of tsetse ………………………………………………………………………………….. 103
2.37.1 Predators …………………………………………………………………………………………………………. 103
2.37.2 Parasites ………………………………………………………………………………………………………….. 103
2.37.3 Parasitoids ……………………………………………………………………………………………………….. 103
2.37.4 Pathogens ………………………………………………………………………………………………………… 104
2.38 Genetic Control of Tsetse Flies …………………………………………………………………………… 104
2.38.1 Transgenesis …………………………………………………………………………………………………….. 104
2.38.2 Sterile Insect Technique (SIT) ……………………………………………………………………………. 105
xv
2.38.3 The Sterile Insect Technique via chemical sterilisation: ………………………………………… 107
2.39 Benefits of Tsetse and Trypanosomiasis Control …………………………………………………. 108
2.40 Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) ………. 108
2.41 Criteria for Tsetse Control Using SIT ………………………………………………………………… 109
CHAPTER THREE ……………………………………………………………………………………………………………….. 110
3.0 MATERIALS AND METHODS ……………………………………………………………………….. 110
3.1 Description of Study Areas ………………………………………………………………………………….. 110
3.1.1 Yankari Game Reserve ……………………………………………………………………………………….. 110
3.1.2 Kainji Lake National Park …………………………………………………………………………………… 113
3.1.3 Old Oyo National Park………………………………………………………………………………………… 115
3.1.4 Cross River National Park …………………………………………………………………………………… 115
3.1.5 Ijah Gwari …………………………………………………………………………………………………………. 118
3.2 Entry Permit into National Parks ………………………………………………………………………… 118
3.3 Methodology ……………………………………………………………………………………………………….. 120
3.3.1 Sample collection, handling and documentation: ……………………………………………………. 120
3.3.2 Mapping of Glossina species distribution using the Global Positioning System (GPS) .. 120
3.3.3 Micro climatic conditions in National Parks ………………………………………………………….. 122
3.3.4 Species composition, relative abundance and distribution ……………………………………….. 122
3.3.5 Apparent density of Glossina species in sampled locations ……………………………………… 122
3.3.6 Sex ratio ……………………………………………………………………………………………………………. 122
3.3.7 Teneral and non-teneral flies ……………………………………………………………………………….. 123
3.3.8 Hunger staging …………………………………………………………………………………………………… 123
3.3.9 Collection and preservation of tsetse fly tissues for genetic analysis …………………………. 124
3.4 Molecular Studies………………………………………………………………………………………………… 124
3.4.1 DNA Extraction …………………………………………………………………………………………………. 124
xvi
3.4.2 DNA Quantification ……………………………………………………………………………………………. 125
3.4.3 Preparation of Master Mix …………………………………………………………………………………… 126
3.4.4 PCR Amplifications ……………………………………………………………………………………………. 126
3.4.5 Preparation of Agarose Gel ………………………………………………………………………………….. 126
3.4.6 Gel Electrophoresis …………………………………………………………………………………………….. 127
3.4.7 Purification of DNA samples for sequencing …………………………………………………………. 127
3.4.8 Sequensing reactions …………………………………………………………………………………………… 128
3.4.9 Sequencing ………………………………………………………………………………………………………… 128
3.5 Data Analyses ……………………………………………………………………………………………………… 128
3.5.1 Differential Statistics ………………………………………………………………………………………….. 128
3.6 Genetic Analyses …………………………………………………………………………………………………. 129
3.6.1 Sequence alignments …………………………………………………………………………………………… 129
3.6.2 Molecular species identification …………………………………………………………………………… 129
3.6.3 Haplotype diversity …………………………………………………………………………………………….. 130
3.6.4 Nucleotide diversity (Genetic variation) ………………………………………………………………… 130
3.6.5 Genetic differentiation (Average Evolutionary Divergence) …………………………………….. 131
3.6.6 Phylogenetic relationships …………………………………………………………………………………… 132
3.7 Geometric Wing Morphometrics………………………………………………………………………….. 132
CHAPTER FOUR ………………………………………………………………………………………………………………….. 134
4.0 RESULTS …………………………………………………………………………………………………………… 134
4.1 Ecological Studies………………………………………………………………………………………………… 134
4.1.1 Glossina species composition and relative abundance …………………………………………….. 134
4.1.2 Glossina spp. distribution in the National Parks and Ijah Gwari ……………………………….. 139
4.1.3 Glossina spp. distribution in relation to ambient temperature and relative humidity conditions …………………………………………………………………………………………………………….. 141
xvii
4.1.4 Apparent density of tsetse fly populations in the National Parks and Ijah Gwari ………… 159
4.1.5 Sex ratio ……………………………………………………………………………………………………………. 161
4.1.6 Teneral and non-teneral flies ……………………………………………………………………………….. 163
4.1.7 Hunger staging …………………………………………………………………………………………………… 163
4.2 Molecular Studies………………………………………………………………………………………………… 166
4.2.1 Amplifications……………………………………………………………………………………………………. 166
4.2.2 Molecular species identification …………………………………………………………………………… 166
4.2.3 Characteristics of CO1 sequences of Glossina spp. in sampled locations …………………… 171
4.2.4 Haplotype diversity …………………………………………………………………………………………….. 177
4.2.5 Nucleotide diversity (Genetic variations) ………………………………………………………………. 177
4.3 Genetic Differentiation (Average Evolutionary Divergence) in Sampled Glossina spp………………………………………………………………………………………………………………………. 187
4.3.1 G. m. submorsitans populations in Yankari Game Reserve ……………………………………… 187
4.3.2 G. m. submorsitans populations in Kainji Lake National Park………………………………….. 187
4.3.3 G. tachinoides populations in Yankari Game Reserve …………………………………………….. 187
4.3.4 G. tachinoides populations in Kainji Lake National Park ………………………………………… 192
4.3.5 G. p. palpalis populations in Old Oyo National Park ………………………………………………. 192
4.3.6 G. p. palpalis populations in Cross River National Park ………………………………………….. 192
4.3.7 G. p. palpalis populations in Ijah Gwari ………………………………………………………………… 192
4.4 Phylogenetic Relationships of Glossina Species in National Parks and Ijah Gwari …. 198
4.5 Phylogenetic Relationships with Particular Reference to G. p. palpalis Populations .. 198
4.6 ITS-1 Analysis …………………………………………………………………………………………………….. 201
4.7 Geometric Wing Morphometrics………………………………………………………………………….. 202
CHAPTER FIVE …………………………………………………………………………………………………………………… 206
5.0 DISCUSSION ……………………………………………………………………………………………………… 206
xviii
5.1 Ecological Studies………………………………………………………………………………………………… 206
5.1.1 Glossina species composition and relative abundance in National Parks and Ijah Gwari…………………………………………………………………………………………………………………… 206
5.1.2 Yankari Game Reserve ……………………………………………………………………………………….. 206
5.1.3 Kainji Lake National Park …………………………………………………………………………………… 209
5.1.4 Old Oyo National Park………………………………………………………………………………………… 210
5.1.5 Cross River National Park …………………………………………………………………………………… 212
5.1.6 Ijah Gwari …………………………………………………………………………………………………………. 213
5.1.7 Glossina spp. distribution in the National Parks and Ijah Gwari ……………………………….. 216
5.1.8 Glossina spp. distribution in relation to ambient temperature and relative humidity conditions. ……………………………………………………………………………………………………………. 217
5.2 Apparent Density of Tsetse Fly Populations in the National Parks and Ijah Gwari … 222
5.3 Sex Ratio …………………………………………………………………………………………………………….. 227
5.4 Teneral and Non-Teneral Flies …………………………………………………………………………….. 230
5.5 Hunger Staging……………………………………………………………………………………………………. 230
5.6 Molecular Studies………………………………………………………………………………………………… 231
5.6.1 Amplifications……………………………………………………………………………………………………. 231
5.6.2 Molecular species identification …………………………………………………………………………… 231
5.6.3 Characteristics of CO1 sequences of Glossina spp. in sampled locations …………………… 232
5.6.4 Haplotype diversity (Genetic variability) ………………………………………………………………. 233
5.6.5 Nucleotide diversity (Genetic variation) ………………………………………………………………… 233
5.7 Genetic Differentiation in Glossina spp. in Sampled Locations ……………………………… 236
5.7.1 G. m. submorsitans populations in Yankari Game Reserve ……………………………………… 236
5.7.2 G. m. submorsitans populations in Kainji Lake National Park………………………………….. 237
5.7.3 G. tachinoides populations in Yankari Game Reserve …………………………………………….. 237
5.7.4 G. tachinoides populations in Kainji Lake National Park ………………………………………… 238
xix
5.7.5 G. p. palpalis populations in Old Oyo National Park ………………………………………………. 238
5.7.6 G. p. palpalis populations in Cross River National Park ………………………………………….. 238
5.7.7 G. p. palpalis populations in Ijah Gwari ………………………………………………………………… 239
5.8 Phylogenetic Relationships of Glossina species in National Parks and Ijah Gwari ….. 241
5.9 Phylogenetic Relationships with Particular Reference to Glossina palpalis palpalis Populations. ………………………………………………………………………………………………………… 244
5.10 Internal Transcribed Spacer (ITS)-1 Analysis …………………………………………………….. 250
5.11 Geometric Wing Morphometrics………………………………………………………………………… 250
CHAPTER SIX ……………………………………………………………………………………………………………………… 252
6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS ………………………………………. 252
6.1 Summary …………………………………………………………………………………………………………….. 252
6.2 Conclusion ………………………………………………………………………………………………………….. 255
6.3 Recommendations ……………………………………………………………………………………………….. 256
REFERENCES ………………………………………………………………………………………………………………………. 257
APPENDICES ……………………………………………………………………………………………………………………….. 297Content Page
TITLE PAGE ………………………………………………………………………………………………………………………………. i
DECLARATION ………………………………………………………………………………………………………………………… ii
CERTIFICATION ……………………………………………………………………………………………………………………… iii
AKNOWLEDGEMENTS ……………………………………………………………………………………………………………. iv
DEDICATION …………………………………………………………………………………………………………………………… vi
ABSTRACT ……………………………………………………………………………………………………………………………… vii
TABLE OF CONTENTS ……………………………………………………………………………………………………………… x
LIST OF TABLES …………………………………………………………………………………………………………………….. xx
LIST OF FIGURES ………………………………………………………………………………………………………………….. xxi
LIST OF PLATES ………………………………………………………………………………………………………………….. xxvi
LIST OF APPENDICES …………………………………………………………………………………………………………. xxvii
LIST OF ABREVIATIONS/ACRONYMS ………………………………………………………………………………… xxix
CHAPTER ONE ……………………………………………………………………………………………………………………….. 1
1.0 INTRODUCTION…………………………………………………………………………………………………… 1
1.1 Preamble ………………………………………………………………………………………………………………… 1
1.2 Statement of the Research Problem …………………………………………………………………………. 7
1.3 Justification ……………………………………………………………………………………………………………. 7
1.4 Aim and Objectives …………………………………………………………………………………………………. 8
xi
1.4.1 Aim ……………………………………………………………………………………………………………………… 8
1.4.2 Objectives …………………………………………………………………………………………………………….. 8
1.5 Research Questions …………………………………………………………………………………………………. 8
CHAPTER TWO …………………………………………………………………………………………………………………….. 10
2.0 LITERATURE REVIEW ……………………………………………………………………………………… 10
2.1 Economic Importance of Trypanosomiasis …………………………………………………………….. 10
2.2 The Causative Agent – Trypanosoma species …………………………………………………………… 13
2.2.1 Description of trypanosome …………………………………………………………………………………… 13
2.2.2 Classification of trypanosomes ………………………………………………………………………………. 15
2.2.3 Life cycle of trypanosomes and disease distribution …………………………………………………. 15
2.2.3.1 Life cycle of trypanosomes ………………………………………………………………………………….. 15
2.2.3.2 Disease distribution …………………………………………………………………………………………… 18
2.2.4 Historical trends …………………………………………………………………………………………………… 21
2.3 Trypanosome –Tsetse Interaction ………………………………………………………………………….. 25
2.4 Evasion of Host Immune System by Trypanosomes ………………………………………………… 26
2.4.1 Variant Surface Glycoprotein (VSG) ………………………………………………………………………. 26
2.4.2 Anti-pathogenicity inducing “host” factors ……………………………………………………………… 26
2.5 Tsetse Flies ……………………………………………………………………………………………………………. 27
2.6 Male and Female Flies Differentiation ……………………………………………………………………. 30
2.7 Glossina Identification …………………………………………………………………………………………… 32
2.8 Tsetse Life History and Biology ……………………………………………………………………………… 34
2.8.1 Mating ………………………………………………………………………………………………………………… 34
2.8.2 Ovulation…………………………………………………………………………………………………………….. 34
2.8.3 Egg stage …………………………………………………………………………………………………………….. 34
2.8.4 Larval and pupal stages …………………………………………………………………………………………. 36
xii
2.8.5 Adult Emergence …………………………………………………………………………………………………. 36
2.9 Teneral and Non-Teneral Flies ………………………………………………………………………………. 37
2.10 Age Determination in Male and Female Flies ……………………………………………………….. 37
2.10.1 Wing fray analysis in males …………………………………………………………………………………. 37
2.10.2 Ovarian configuration in female flies ……………………………………………………………………. 41
2.11 Physiological States in Female Flies ……………………………………………………………………… 43
2.12 Hunger Staging……………………………………………………………………………………………………. 43
2.13 Tsetse Ecology …………………………………………………………………………………………………….. 44
2.14 Survival and Longevity of Tsetse Flies………………………………………………………………….. 45
2.15 Activity Cycle ……………………………………………………………………………………………………… 45
2.16 Feeding Behaviour and Host Selection …………………………………………………………………. 46
2.17 Host Detection …………………………………………………………………………………………………….. 47
2.18 Resting Behaviour ……………………………………………………………………………………………….. 48
2.19 Classification of Tsetse Flies ………………………………………………………………………………… 49
2.20 Distinctive Characteristics …………………………………………………………………………………… 50
2.20.1 G. palpalis group ……………………………………………………………………………………………….. 50
2.20.1.1 G. tachinoides …………………………………………………………………………………………………. 51
2.20.1.2 G. palpalis and G. fuscipes ……………………………………………………………………………….. 51
2.20.1.3 G. pallicera and G. caliginea …………………………………………………………………………….. 51
2.20.2 G. morsitans group……………………………………………………………………………………………… 51
2.20.3 G. fusca group ……………………………………………………………………………………………………. 52
2.21 Tsetse Fly Distribution and Abundance ……………………………………………………………….. 53
2.21.1 Historical trends …………………………………………………………………………………………………. 53
2.21.2 Speciation in tsetse flies ………………………………………………………………………………………. 53
2.21.3 Phylogeny of Glossina ………………………………………………………………………………………… 54
xiii
2.21.4 Glossina distribution …………………………………………………………………………………………… 55
2.21.5 Tsetse distribution in Nigeria ……………………………………………………………………………….. 59
2.21.6 Tsetse flies in Nigeria National Parks and Game Reserves ………………………………………. 64
2.22 Dispersal in Tsetse Flies……………………………………………………………………………………….. 68
2.23 Disease Transmission …………………………………………………………………………………………… 70
2.23.1 Cyclic transmission …………………………………………………………………………………………….. 70
2.23.2 Non-cyclic transmission (Mechanical transmission) ……………………………………………….. 73
2.24 Vectorial Capacity and Transmission Potential…………………………………………………….. 74
2.25 Infection Rates in Tsetse ………………………………………………………………………………………. 74
2.26 Tsetse Immunity ………………………………………………………………………………………………….. 76
2.27 Tsetse Sampling …………………………………………………………………………………………………… 78
2.27.1 Fly rounds …………………………………………………………………………………………………………. 79
2.27.2 Traps ………………………………………………………………………………………………………………… 80
2.27.3 Electric nets ……………………………………………………………………………………………………….. 81
2.27.4 Visual and olfactory attractants of tsetse flies ………………………………………………………… 81
2.27.5 Screens, targets and traps …………………………………………………………………………………….. 81
2.27.6 Odour attractants ………………………………………………………………………………………………… 82
2.28 Population Dynamics …………………………………………………………………………………………… 83
2.29 Population Analysis …………………………………………………………………………………………….. 84
2.30 Genetic Variation in Tsetse Flies ………………………………………………………………………….. 85
2.30.1 Laboratory studies ………………………………………………………………………………………………. 85
2.30.2 Variation in natural populations……………………………………………………………………………. 86
2.31 Genetic Markers in Tsetse Flies……………………………………………………………………………. 87
2.32 Biochemical / Protein Markers …………………………………………………………………………….. 87
2.32.1 Allozymes …………………………………………………………………………………………………………. 87
xiv
2.33 Molecular / DNA Markers …………………………………………………………………………………… 88
2.33.1 Microsatellites ……………………………………………………………………………………………………. 88
2.33.2 Mitochondrial DNA (mtDNA) …………………………………………………………………………….. 89
2.34 Geometry Wing Morphometrics ………………………………………………………………………….. 90
2.35 Tsetse and Trypanosomiasis Control ……………………………………………………………………. 91
2.35.1 Control of trypanosomiasis using Chemotherapy and Chemoprophylaxis ………………….. 91
2.35.2 Use of trypanosome resistant (Trypanotolerant) breeds …………………………………………… 93
2.36 Tsetse Control……………………………………………………………………………………………………… 93
2.36.1 Direct destruction of tsetse flies ……………………………………………………………………………. 94
2.36.2 Tsetse control by game elimination ………………………………………………………………………. 94
2.36.3 Tsetse fly control by bush clearing ……………………………………………………………………….. 95
2.36.4 Tsetse control by population resettlement ……………………………………………………………… 96
2.36.5 Tsetse control by aerial spraying of insecticides …………………………………………………….. 97
2.36.6 Tsetse control by ground spraying of insecticides …………………………………………………… 98
2.36.7 Trapping ……………………………………………………………………………………………………………. 99
2.36.8 Insecticide treated traps and targets …………………………………………………………………….. 100
2.36.9 Pour-on formulations ………………………………………………………………………………………… 102
2.37 Biological control of tsetse ………………………………………………………………………………….. 103
2.37.1 Predators …………………………………………………………………………………………………………. 103
2.37.2 Parasites ………………………………………………………………………………………………………….. 103
2.37.3 Parasitoids ……………………………………………………………………………………………………….. 103
2.37.4 Pathogens ………………………………………………………………………………………………………… 104
2.38 Genetic Control of Tsetse Flies …………………………………………………………………………… 104
2.38.1 Transgenesis …………………………………………………………………………………………………….. 104
2.38.2 Sterile Insect Technique (SIT) ……………………………………………………………………………. 105
xv
2.38.3 The Sterile Insect Technique via chemical sterilisation: ………………………………………… 107
2.39 Benefits of Tsetse and Trypanosomiasis Control …………………………………………………. 108
2.40 Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) ………. 108
2.41 Criteria for Tsetse Control Using SIT ………………………………………………………………… 109
CHAPTER THREE ……………………………………………………………………………………………………………….. 110
3.0 MATERIALS AND METHODS ……………………………………………………………………….. 110
3.1 Description of Study Areas ………………………………………………………………………………….. 110
3.1.1 Yankari Game Reserve ……………………………………………………………………………………….. 110
3.1.2 Kainji Lake National Park …………………………………………………………………………………… 113
3.1.3 Old Oyo National Park………………………………………………………………………………………… 115
3.1.4 Cross River National Park …………………………………………………………………………………… 115
3.1.5 Ijah Gwari …………………………………………………………………………………………………………. 118
3.2 Entry Permit into National Parks ………………………………………………………………………… 118
3.3 Methodology ……………………………………………………………………………………………………….. 120
3.3.1 Sample collection, handling and documentation: ……………………………………………………. 120
3.3.2 Mapping of Glossina species distribution using the Global Positioning System (GPS) .. 120
3.3.3 Micro climatic conditions in National Parks ………………………………………………………….. 122
3.3.4 Species composition, relative abundance and distribution ……………………………………….. 122
3.3.5 Apparent density of Glossina species in sampled locations ……………………………………… 122
3.3.6 Sex ratio ……………………………………………………………………………………………………………. 122
3.3.7 Teneral and non-teneral flies ……………………………………………………………………………….. 123
3.3.8 Hunger staging …………………………………………………………………………………………………… 123
3.3.9 Collection and preservation of tsetse fly tissues for genetic analysis …………………………. 124
3.4 Molecular Studies………………………………………………………………………………………………… 124
3.4.1 DNA Extraction …………………………………………………………………………………………………. 124
xvi
3.4.2 DNA Quantification ……………………………………………………………………………………………. 125
3.4.3 Preparation of Master Mix …………………………………………………………………………………… 126
3.4.4 PCR Amplifications ……………………………………………………………………………………………. 126
3.4.5 Preparation of Agarose Gel ………………………………………………………………………………….. 126
3.4.6 Gel Electrophoresis …………………………………………………………………………………………….. 127
3.4.7 Purification of DNA samples for sequencing …………………………………………………………. 127
3.4.8 Sequensing reactions …………………………………………………………………………………………… 128
3.4.9 Sequencing ………………………………………………………………………………………………………… 128
3.5 Data Analyses ……………………………………………………………………………………………………… 128
3.5.1 Differential Statistics ………………………………………………………………………………………….. 128
3.6 Genetic Analyses …………………………………………………………………………………………………. 129
3.6.1 Sequence alignments …………………………………………………………………………………………… 129
3.6.2 Molecular species identification …………………………………………………………………………… 129
3.6.3 Haplotype diversity …………………………………………………………………………………………….. 130
3.6.4 Nucleotide diversity (Genetic variation) ………………………………………………………………… 130
3.6.5 Genetic differentiation (Average Evolutionary Divergence) …………………………………….. 131
3.6.6 Phylogenetic relationships …………………………………………………………………………………… 132
3.7 Geometric Wing Morphometrics………………………………………………………………………….. 132
CHAPTER FOUR ………………………………………………………………………………………………………………….. 134
4.0 RESULTS …………………………………………………………………………………………………………… 134
4.1 Ecological Studies………………………………………………………………………………………………… 134
4.1.1 Glossina species composition and relative abundance …………………………………………….. 134
4.1.2 Glossina spp. distribution in the National Parks and Ijah Gwari ……………………………….. 139
4.1.3 Glossina spp. distribution in relation to ambient temperature and relative humidity conditions …………………………………………………………………………………………………………….. 141
xvii
4.1.4 Apparent density of tsetse fly populations in the National Parks and Ijah Gwari ………… 159
4.1.5 Sex ratio ……………………………………………………………………………………………………………. 161
4.1.6 Teneral and non-teneral flies ……………………………………………………………………………….. 163
4.1.7 Hunger staging …………………………………………………………………………………………………… 163
4.2 Molecular Studies………………………………………………………………………………………………… 166
4.2.1 Amplifications……………………………………………………………………………………………………. 166
4.2.2 Molecular species identification …………………………………………………………………………… 166
4.2.3 Characteristics of CO1 sequences of Glossina spp. in sampled locations …………………… 171
4.2.4 Haplotype diversity …………………………………………………………………………………………….. 177
4.2.5 Nucleotide diversity (Genetic variations) ………………………………………………………………. 177
4.3 Genetic Differentiation (Average Evolutionary Divergence) in Sampled Glossina spp………………………………………………………………………………………………………………………. 187
4.3.1 G. m. submorsitans populations in Yankari Game Reserve ……………………………………… 187
4.3.2 G. m. submorsitans populations in Kainji Lake National Park………………………………….. 187
4.3.3 G. tachinoides populations in Yankari Game Reserve …………………………………………….. 187
4.3.4 G. tachinoides populations in Kainji Lake National Park ………………………………………… 192
4.3.5 G. p. palpalis populations in Old Oyo National Park ………………………………………………. 192
4.3.6 G. p. palpalis populations in Cross River National Park ………………………………………….. 192
4.3.7 G. p. palpalis populations in Ijah Gwari ………………………………………………………………… 192
4.4 Phylogenetic Relationships of Glossina Species in National Parks and Ijah Gwari …. 198
4.5 Phylogenetic Relationships with Particular Reference to G. p. palpalis Populations .. 198
4.6 ITS-1 Analysis …………………………………………………………………………………………………….. 201
4.7 Geometric Wing Morphometrics………………………………………………………………………….. 202
CHAPTER FIVE …………………………………………………………………………………………………………………… 206
5.0 DISCUSSION ……………………………………………………………………………………………………… 206
xviii
5.1 Ecological Studies………………………………………………………………………………………………… 206
5.1.1 Glossina species composition and relative abundance in National Parks and Ijah Gwari…………………………………………………………………………………………………………………… 206
5.1.2 Yankari Game Reserve ……………………………………………………………………………………….. 206
5.1.3 Kainji Lake National Park …………………………………………………………………………………… 209
5.1.4 Old Oyo National Park………………………………………………………………………………………… 210
5.1.5 Cross River National Park …………………………………………………………………………………… 212
5.1.6 Ijah Gwari …………………………………………………………………………………………………………. 213
5.1.7 Glossina spp. distribution in the National Parks and Ijah Gwari ……………………………….. 216
5.1.8 Glossina spp. distribution in relation to ambient temperature and relative humidity conditions. ……………………………………………………………………………………………………………. 217
5.2 Apparent Density of Tsetse Fly Populations in the National Parks and Ijah Gwari … 222
5.3 Sex Ratio …………………………………………………………………………………………………………….. 227
5.4 Teneral and Non-Teneral Flies …………………………………………………………………………….. 230
5.5 Hunger Staging……………………………………………………………………………………………………. 230
5.6 Molecular Studies………………………………………………………………………………………………… 231
5.6.1 Amplifications……………………………………………………………………………………………………. 231
5.6.2 Molecular species identification …………………………………………………………………………… 231
5.6.3 Characteristics of CO1 sequences of Glossina spp. in sampled locations …………………… 232
5.6.4 Haplotype diversity (Genetic variability) ………………………………………………………………. 233
5.6.5 Nucleotide diversity (Genetic variation) ………………………………………………………………… 233
5.7 Genetic Differentiation in Glossina spp. in Sampled Locations ……………………………… 236
5.7.1 G. m. submorsitans populations in Yankari Game Reserve ……………………………………… 236
5.7.2 G. m. submorsitans populations in Kainji Lake National Park………………………………….. 237
5.7.3 G. tachinoides populations in Yankari Game Reserve …………………………………………….. 237
5.7.4 G. tachinoides populations in Kainji Lake National Park ………………………………………… 238
xix
5.7.5 G. p. palpalis populations in Old Oyo National Park ………………………………………………. 238
5.7.6 G. p. palpalis populations in Cross River National Park ………………………………………….. 238
5.7.7 G. p. palpalis populations in Ijah Gwari ………………………………………………………………… 239
5.8 Phylogenetic Relationships of Glossina species in National Parks and Ijah Gwari ….. 241
5.9 Phylogenetic Relationships with Particular Reference to Glossina palpalis palpalis Populations. ………………………………………………………………………………………………………… 244
5.10 Internal Transcribed Spacer (ITS)-1 Analysis …………………………………………………….. 250
5.11 Geometric Wing Morphometrics………………………………………………………………………… 250
CHAPTER SIX ……………………………………………………………………………………………………………………… 252
6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS ………………………………………. 252
6.1 Summary …………………………………………………………………………………………………………….. 252
6.2 Conclusion ………………………………………………………………………………………………………….. 255
6.3 Recommendations ……………………………………………………………………………………………….. 256
REFERENCES ………………………………………………………………………………………………………………………. 257
APPENDICES ……………………………………………………………………………………………………………………….. 297

 

 

CHAPTER ONE

1.0 INTRODUCTION
1.1 Preamble
African Trypanosomiasis is a debilitating tropical disease complex of humans and livestock caused by protozoan parasites of the Genus Trypanosoma. The disease is the major cause of extensive morbidity and mortality in affected individuals and livestock across 38 endemic countries of sub-Saharan Africa (Leak, 1999). It is the major impediment to profitable agriculture and livestock development in the poverty stricken sub-region (Swallow, 2000).
Animal African trypanosomiasis (AAT) otherwise called “nagana” in cattle, is a wasting disease responsible for the death of about three million cattle annually and other breeds of livestock in sub-Saharan Africa (Abenga et al., 2002; Mulumba, 2003). Losses due to AAT alone are estimated at approximately 4.5 billion United States dollars (Hursey, 2001). Large areas of fertile land have been abandoned, and therefore not utilized for agricultural purposes. Animal African trypanosomiasis (AAT) impacts negatively on the socio-economic and political wellbeing of teeming human populations in affected countries (Nash, 1958). The resultant effects of these on large scale is food insecurity, low protein intake, low manure for local organic food production, low income from sale of farm produce, lack of employment and national insecurity (Swallow, 1999).
In Nigeria, losses due to AAT are estimated at about 837.20 million Naira in six states of the Federation (NARP/NITR Mid Term Review, 1998), largely because tsetse and trypanosomiasis have altered the economic health and social status of inhabitants of affected areas in the country. Nigeria, despite its cattle population of over 16 million head (FAO 2004), is the largest importer of meat and dairy products in West Africa (Bonnet et al., 2015).
2
Human African trypanosomiasis (HAT) otherwise called “Sleeping sickness” occurs in an area approximately 1.55 million Km2 with over 70 million people mainly living in rural areas at risk of the disease (Aksoy et al., 2017). The World Health Organisation (WHO) estimates the disease burden at 2.05 million disability adjusted life years (WHO, 2006). Epidemics of sleeping sickness which ravaged sub-Saharan African countries affected by the disease in the twentieth century, caused massive human displacement and depopulation (Steverding, 2008, Simarro et al., 2012). Though the situation was brought under control, in the 1960s, it resurged again in the 1980s (Curtain, 2015), due mainly to economic decline, civil disturbances, war, population movements and refugees (Smith, 1998). The gradual encroachment of people into tsetse infested areas as a result of war, civil disturbances may be responsible for the resurgence of sleeping sickness in areas where the disease had previously been eliminated as observed in the Republic of Congo, Southern Sudan and Rwanda (Lyons, 1992; Arbyn et al., 1995; More and Richer, 2001; Stanghellini and Josenado, 2001; Aksoy et al., 2003; Büscher et al., 2017). However the number of new cases of HAT in 2009 declined to below 10,000 for the first time in 50 years as against 30,000 reported in 1999 and 2804 reported in 2015 (WHO, 2018) due mainly to the improvement of surveillance and treatment activities (Simarro et al., 2011). Even though, with concerted efforts through active surveillance and treatment of infected individuals, the epidemic situation has been brought under control, sleeping sickness still remains endemic in many countries in sub-Saharan Africa, including Nigeria (Franco et al., 2014).
In Nigeria, the disease which was previously regarded as a northern problem and conquered in the 1960s is re-emerging, with a shift to the south of the country (Edeghere et al., 1989; Anere et al., 2006; Curtain, 2008; Adamu et al., 2011). Reports of active surveillance activities have shown that the disease is on the rise even though the WHO has grouped the country amongst those with
3
low sleeping sickness cases (Onyebiguwa et al., 2010; Franco et al., 2014; Karshima et al., 2016; WHO, 2017). In February, 2010, out of 470 subjects screened in Delta State Nigeria, 4 (0.85%) were parasitologically positive and 44 (9.34%) were serologically positive for trypanosomes (NITR unpublished report). In 2011, out of two reported cases (North and South), one was confirmed CATT positive and died (NITR unpublished report).
Trypanosomes are the causative agents of trypanosomiasis. They are single celled protozoan parasites belonging to the genus Trypanosoma. They are transmitted from host to host via the bite of infected blood-sucking insect, tsetse fly (Glossina species). The most economically important trypanosome parasites transmitted in livestock include Trypanosoma vivax, T. congolense, T. brucei, T. simiae, and T. evansi. Two sub-species of T. brucei that are responsible for the disease in humans include T. brucei gambiense, which causes the chronic form of the disease in west and central Africa, and T. brucei rhodesiense that causes the acute form in east and southern Africa where it is a zoonosis. The T. brucei forms that cause the disease in humans and animals are morphologically identical except that the animal parasites are susceptible to a trypanocidal factor due to the presence of a high density lipoprotein associated with the human blood (Rickman and Robson, 1970; Jenni and Brun, 1982; Hager and Hajduk, 1997). The trypanosome parasites that cause trypanosomiasis in both humans and animals are transmitted cyclically by the bites of infected tsetse flies (Glossina species) during blood meals. Other biting flies including tabanus, stomoxys and haematopota have been incriminated in the non-cyclic transmission of the disease in animals (Bitome-Essono, 2015).
Tsetse flies (Glossina species) are obligate haematophagous insects of human and animal hosts occupying about 10 million Km2 (78 %) of the total land mass of the region of sub-Saharan Africa traversing the continent between latitude 14o North and 20o South (Swallow et al., 1998). There
4
are 34 extant species and subspecies of tsetse flies distributed across 38 sub- Saharan African countries (Davies, 1977). Within their confines, tsetse flies are not uniformly distributed, but are distributed discontinuously due to habitat fragmentation (Krafsur, 2009). Added to that is the influence of environmental factors such as temperature, relative humidity, elevation, rainfall and vegetation cover on the relative abundance of the fly populations (Rogers, 1977; Brightwell et al., 1992; Robinson, et al., 1997a; 1997b). The above listed environmental factors in addition to host availability (Rogers and Boreham, 1973; Turner, 1981), cause uneven distribution of tsetse flies between vegetation types. Environmental changes (i.e. land use due to increasing human population and deforestation) have been implicated in the changing pattern of the epidemiology of trypanosomiasis (Van den Bossche et al., 2001; 2010). Tsetse flies exist in geographically isolated units or subpopulations in which flies are adapted to and may be responsible for the observed intraspecific geographical variation in behavior and host preferences (Torr et al., 1988; Colvin and Gibson, 1992).
Out of the 34 extant species and subspecies of tsetse flies so far described, 11 occur in Nigeria covering an area approximately 75-80% of Nigeria’s 928,300 square kilometers total land mass. They are distributed according to habitat preferences between Mangroove swamp vegetation from the coast, through rainforest, derived savanna to Northern guinea /Sahel savannah, between latitude 12-13onorth with extensions along Hadejia-Jama’are hydrographic networks (Davies, 1977; Onyiah et al., 1983). Exceptions include areas above 1,200 meters above sea level (Dede et al., 2005). However, it has recently been observed that tsetse infestations have extended into areas in which they were previously not recorded probably due to the phenomenon of global warming (Jordan, 1989; Kalu, 1996; Aksoy et al., 2003; Dede et al., 2005; Ogedegbe and Rotimi, 2006; Tongue et al., 2015)
5
All the 11 species and subspecies of tsetse in Nigeria are capable of transmitting animal trypanosomiasis, the most important being G. m. submorsitans, G. longipalpis, G. tachinoides and G. p. palpalis (Davies, 1977). Two members of the riverine group, (Glossina palpalis palpalis and Glossina tachinoides), in addition to transmitting animal trypanosomiasis, are able to transmit human trypanosomiasis. It is estimated that if tsetse and trypanosomiasis are eradicated and the area presently occupied by tsetse flies is opened up and put into full utilization, it could support additional 2.5-3.2 times the country’s current estimated livestock population (Onyiah, 1997). In addition, the country could save approximately US $1.3 billion from the importation of meat and dairy products annually, and ensure increased employment opportunities, food availability and national security.
In view of the negative impact of trypanosomiasis on the economy of most countries affected by the disease, the African Heads of State and Government during the 36th Conference of African Union (AU) at Lome, Togo, declared through resolution AHG/Dec.156 (XXXVI), of 12 July, 2000, that tsetse flies be eliminated from the African continent through the Pan Africa Tsetse and Trypanosomiasis Eradication Campaign (PATTEC)
Control of trypanosomiasis relies on the deliberate actions against the trypanosome parasites, the vector and/or the host. The disease could be controlled either by chemotherapy or chemoprophylaxis. However in view of the lack of effective vaccine against the parasites (Nok, 2005), due to the phenomenon of variable surface glycoproteins in trypanosomes (Barry, 1997; Pays et al., 2004), unavailability and high cost of drugs, resistance of parasites to available drugs, vector control is considered the most effective method of trypanosomiasis control (Ravel, 2007). The vector could be controlled by means of aerial or ground application of chemical insecticides, impregnated screens and targets, pour- on formulations used on animals and the use of Sterile
6
Insect Technique (SIT) for mop up operations (Allsop, 2001). However, despite concerted efforts to control tsetse flies, these efforts are hampered by the reinvasion of cleared areas by other tsetse flies (Aksoy, 2003; Krafsur et al., 2008; Beadell et al., 2010). The limiting factors have mainly been attributed to inadequate knowledge on the dynamics of fly populations. Invariably, adequate knowledge on the population dynamics of tsetse flies is key to successful control of tsetse flies using the Sterile Insect Technique (Feldmann et al., 2005; Hendrichs, et al., 2005; Torr et al., 2006).
Earlier laboratory studies had shown that tsetse populations could be differentiated (Van Etten, 1981; 1982a; 1982b; Torr et al., 1988; Colvin and Gibson, 1992; Moloo, 1992, 1993), but genetic basis of the differences were never investigated probably due to limited availability of molecular tools. With the current availability of molecular tools, studies have shown that the genetic basis of differentiations in tsetse populations could be investigated. It is possible for instance to employ molecular tools to provide data on genetic differentiations of tsetse populations, using either mitochondrial or microsatellite DNA markers (Solano et al., 1999, 2000; Krafsur 2003; Marqueze et al., 2004). Cytochrome oxidase1 gene which is important in oxidative activities during metabolism is a maternally inherited gene found in Mitochondrial DNA that could be used to assess genetic drift and bottlenecks in population size (Avise, 1994). It is a conserved gene and relatively stable, whereas Microsatellites are short repetitive nucleotide sequences with conserved flanking regions that could be amplified by polymerase chain reactions (Krafsur and Endsley, 2002). These techniques rapidly identify the levels of epidemiologically important population sub-structuring in tsetse fly vectors.
Investigating genetic variations in natural populations of Glossina species is imperative for ascertaining the success or otherwise of tsetse control programme using SIT. Where there is limited
7
gene flow for instance, SIT may succeed because chances of reinvasion from neighbouring populations may be minimal, but where there is no restriction to gene flow, the success of control campaign using SIT cannot be guaranteed (Krafsur, 2003).
To our knowledge, information on the genetic structures of Nigeria tsetse fly populations that would enable planning of effective control strategies against the vectors in the country is limited. Therefore investigating whether Cytochrome oxidase I mtDNA marker could be used to unravel genetic variations in natural tsetse fly populations could improve our understanding of the dynamics of tsetse fly populations in Nigeria and provide some answers. The result from this study might provide information that could aid choice of effective control strategy against tsetse fly vectors in Nigeria, especially as the country is part of the PATTEC campaign of eradication of economically important Glosssina spp. using a component of SIT.
1.2 Statement of the Research Problem
Despite concerted efforts to control tsetse flies, reinvasion of cleared areas by other tsetse flies often occurs due primarily to inadequate knowledge on the population dynamics of target Glosssina species and their role in disease transmission Ecological data needs to be supported by molecular techniques in providing clearer understanding on the extent of dispersal, delineation of cryptic species boundry, isolation and disease transmission potentials of a given target tsetse population. These are currently limited in Nigeria.
1.3 Justification
Knowledge on the population structure of tsetse flies is of paramount importance as it is expected to allow for the assessment of the menace of tsetse and trypanosomiasis in the country. Information generated from this study may aid the choice of effective anti-tsetse management approaches in the country’s National Parks using a component of the SIT.
8
1.4 Aim and Objectives
1.4.1 Aim
To evaluate and compare the population genetic structures of Glossina species in Nigeria National Parks and Ijah Gwari, with a view to deciphering underlying changes in species composition.
1.4.2 Objectives
i) To determine the species composition and relative abundance of Glossina populations in some Nigeria National Parks and Ijah Gwari.
ii) To determine the apparent densities and distribution patterns of Glossina populations in Nigeria National Parks in relation to vegetation types and climatic conditions
iii) To determine genetic structures of Glossina species in Nigeria National Parks and Ijah Gwari using Cytochrome Oxidase C SU1 (CO1).
iv) To determine the phylogenetic profile/structure of Glossina populations in some Nigeria National Parks and Ijah Gwari.
v) To determine how narrow or wide Glossina populations have drifted in Nigeria National Parks and Ijah Gwari
1.5 Research Questions
i) Is the species composition and relative abundance of Glossina populations in the selected Nigeria National Parks the same?
ii) Are there any variations in the apparent density and distribution patterns in the Glossina populations in relation to vegetation types and climatic conditions in the different National Parks and Ijah Gwari?
9
iii) Are there genetic variations in the different species of Glossina in the different National Parks
iv) Are there variations in the phylogenetic relationship within, among and between the different populations of Glossina spp. in the different National Parks
v) Are the Glossina populations homogenous in the sampled locations?1.0 INTRODUCTION
1.1 Preamble
African Trypanosomiasis is a debilitating tropical disease complex of humans and livestock caused by protozoan parasites of the Genus Trypanosoma. The disease is the major cause of extensive morbidity and mortality in affected individuals and livestock across 38 endemic countries of sub-Saharan Africa (Leak, 1999). It is the major impediment to profitable agriculture and livestock development in the poverty stricken sub-region (Swallow, 2000).
Animal African trypanosomiasis (AAT) otherwise called “nagana” in cattle, is a wasting disease responsible for the death of about three million cattle annually and other breeds of livestock in sub-Saharan Africa (Abenga et al., 2002; Mulumba, 2003). Losses due to AAT alone are estimated at approximately 4.5 billion United States dollars (Hursey, 2001). Large areas of fertile land have been abandoned, and therefore not utilized for agricultural purposes. Animal African trypanosomiasis (AAT) impacts negatively on the socio-economic and political wellbeing of teeming human populations in affected countries (Nash, 1958). The resultant effects of these on large scale is food insecurity, low protein intake, low manure for local organic food production, low income from sale of farm produce, lack of employment and national insecurity (Swallow, 1999).
In Nigeria, losses due to AAT are estimated at about 837.20 million Naira in six states of the Federation (NARP/NITR Mid Term Review, 1998), largely because tsetse and trypanosomiasis have altered the economic health and social status of inhabitants of affected areas in the country. Nigeria, despite its cattle population of over 16 million head (FAO 2004), is the largest importer of meat and dairy products in West Africa (Bonnet et al., 2015).
2
Human African trypanosomiasis (HAT) otherwise called “Sleeping sickness” occurs in an area approximately 1.55 million Km2 with over 70 million people mainly living in rural areas at risk of the disease (Aksoy et al., 2017). The World Health Organisation (WHO) estimates the disease burden at 2.05 million disability adjusted life years (WHO, 2006). Epidemics of sleeping sickness which ravaged sub-Saharan African countries affected by the disease in the twentieth century, caused massive human displacement and depopulation (Steverding, 2008, Simarro et al., 2012). Though the situation was brought under control, in the 1960s, it resurged again in the 1980s (Curtain, 2015), due mainly to economic decline, civil disturbances, war, population movements and refugees (Smith, 1998). The gradual encroachment of people into tsetse infested areas as a result of war, civil disturbances may be responsible for the resurgence of sleeping sickness in areas where the disease had previously been eliminated as observed in the Republic of Congo, Southern Sudan and Rwanda (Lyons, 1992; Arbyn et al., 1995; More and Richer, 2001; Stanghellini and Josenado, 2001; Aksoy et al., 2003; Büscher et al., 2017). However the number of new cases of HAT in 2009 declined to below 10,000 for the first time in 50 years as against 30,000 reported in 1999 and 2804 reported in 2015 (WHO, 2018) due mainly to the improvement of surveillance and treatment activities (Simarro et al., 2011). Even though, with concerted efforts through active surveillance and treatment of infected individuals, the epidemic situation has been brought under control, sleeping sickness still remains endemic in many countries in sub-Saharan Africa, including Nigeria (Franco et al., 2014).
In Nigeria, the disease which was previously regarded as a northern problem and conquered in the 1960s is re-emerging, with a shift to the south of the country (Edeghere et al., 1989; Anere et al., 2006; Curtain, 2008; Adamu et al., 2011). Reports of active surveillance activities have shown that the disease is on the rise even though the WHO has grouped the country amongst those with
3
low sleeping sickness cases (Onyebiguwa et al., 2010; Franco et al., 2014; Karshima et al., 2016; WHO, 2017). In February, 2010, out of 470 subjects screened in Delta State Nigeria, 4 (0.85%) were parasitologically positive and 44 (9.34%) were serologically positive for trypanosomes (NITR unpublished report). In 2011, out of two reported cases (North and South), one was confirmed CATT positive and died (NITR unpublished report).
Trypanosomes are the causative agents of trypanosomiasis. They are single celled protozoan parasites belonging to the genus Trypanosoma. They are transmitted from host to host via the bite of infected blood-sucking insect, tsetse fly (Glossina species). The most economically important trypanosome parasites transmitted in livestock include Trypanosoma vivax, T. congolense, T. brucei, T. simiae, and T. evansi. Two sub-species of T. brucei that are responsible for the disease in humans include T. brucei gambiense, which causes the chronic form of the disease in west and central Africa, and T. brucei rhodesiense that causes the acute form in east and southern Africa where it is a zoonosis. The T. brucei forms that cause the disease in humans and animals are morphologically identical except that the animal parasites are susceptible to a trypanocidal factor due to the presence of a high density lipoprotein associated with the human blood (Rickman and Robson, 1970; Jenni and Brun, 1982; Hager and Hajduk, 1997). The trypanosome parasites that cause trypanosomiasis in both humans and animals are transmitted cyclically by the bites of infected tsetse flies (Glossina species) during blood meals. Other biting flies including tabanus, stomoxys and haematopota have been incriminated in the non-cyclic transmission of the disease in animals (Bitome-Essono, 2015).
Tsetse flies (Glossina species) are obligate haematophagous insects of human and animal hosts occupying about 10 million Km2 (78 %) of the total land mass of the region of sub-Saharan Africa traversing the continent between latitude 14o North and 20o South (Swallow et al., 1998). There
4
are 34 extant species and subspecies of tsetse flies distributed across 38 sub- Saharan African countries (Davies, 1977). Within their confines, tsetse flies are not uniformly distributed, but are distributed discontinuously due to habitat fragmentation (Krafsur, 2009). Added to that is the influence of environmental factors such as temperature, relative humidity, elevation, rainfall and vegetation cover on the relative abundance of the fly populations (Rogers, 1977; Brightwell et al., 1992; Robinson, et al., 1997a; 1997b). The above listed environmental factors in addition to host availability (Rogers and Boreham, 1973; Turner, 1981), cause uneven distribution of tsetse flies between vegetation types. Environmental changes (i.e. land use due to increasing human population and deforestation) have been implicated in the changing pattern of the epidemiology of trypanosomiasis (Van den Bossche et al., 2001; 2010). Tsetse flies exist in geographically isolated units or subpopulations in which flies are adapted to and may be responsible for the observed intraspecific geographical variation in behavior and host preferences (Torr et al., 1988; Colvin and Gibson, 1992).
Out of the 34 extant species and subspecies of tsetse flies so far described, 11 occur in Nigeria covering an area approximately 75-80% of Nigeria’s 928,300 square kilometers total land mass. They are distributed according to habitat preferences between Mangroove swamp vegetation from the coast, through rainforest, derived savanna to Northern guinea /Sahel savannah, between latitude 12-13onorth with extensions along Hadejia-Jama’are hydrographic networks (Davies, 1977; Onyiah et al., 1983). Exceptions include areas above 1,200 meters above sea level (Dede et al., 2005). However, it has recently been observed that tsetse infestations have extended into areas in which they were previously not recorded probably due to the phenomenon of global warming (Jordan, 1989; Kalu, 1996; Aksoy et al., 2003; Dede et al., 2005; Ogedegbe and Rotimi, 2006; Tongue et al., 2015)
5
All the 11 species and subspecies of tsetse in Nigeria are capable of transmitting animal trypanosomiasis, the most important being G. m. submorsitans, G. longipalpis, G. tachinoides and G. p. palpalis (Davies, 1977). Two members of the riverine group, (Glossina palpalis palpalis and Glossina tachinoides), in addition to transmitting animal trypanosomiasis, are able to transmit human trypanosomiasis. It is estimated that if tsetse and trypanosomiasis are eradicated and the area presently occupied by tsetse flies is opened up and put into full utilization, it could support additional 2.5-3.2 times the country’s current estimated livestock population (Onyiah, 1997). In addition, the country could save approximately US $1.3 billion from the importation of meat and dairy products annually, and ensure increased employment opportunities, food availability and national security.
In view of the negative impact of trypanosomiasis on the economy of most countries affected by the disease, the African Heads of State and Government during the 36th Conference of African Union (AU) at Lome, Togo, declared through resolution AHG/Dec.156 (XXXVI), of 12 July, 2000, that tsetse flies be eliminated from the African continent through the Pan Africa Tsetse and Trypanosomiasis Eradication Campaign (PATTEC)
Control of trypanosomiasis relies on the deliberate actions against the trypanosome parasites, the vector and/or the host. The disease could be controlled either by chemotherapy or chemoprophylaxis. However in view of the lack of effective vaccine against the parasites (Nok, 2005), due to the phenomenon of variable surface glycoproteins in trypanosomes (Barry, 1997; Pays et al., 2004), unavailability and high cost of drugs, resistance of parasites to available drugs, vector control is considered the most effective method of trypanosomiasis control (Ravel, 2007). The vector could be controlled by means of aerial or ground application of chemical insecticides, impregnated screens and targets, pour- on formulations used on animals and the use of Sterile
6
Insect Technique (SIT) for mop up operations (Allsop, 2001). However, despite concerted efforts to control tsetse flies, these efforts are hampered by the reinvasion of cleared areas by other tsetse flies (Aksoy, 2003; Krafsur et al., 2008; Beadell et al., 2010). The limiting factors have mainly been attributed to inadequate knowledge on the dynamics of fly populations. Invariably, adequate knowledge on the population dynamics of tsetse flies is key to successful control of tsetse flies using the Sterile Insect Technique (Feldmann et al., 2005; Hendrichs, et al., 2005; Torr et al., 2006).
Earlier laboratory studies had shown that tsetse populations could be differentiated (Van Etten, 1981; 1982a; 1982b; Torr et al., 1988; Colvin and Gibson, 1992; Moloo, 1992, 1993), but genetic basis of the differences were never investigated probably due to limited availability of molecular tools. With the current availability of molecular tools, studies have shown that the genetic basis of differentiations in tsetse populations could be investigated. It is possible for instance to employ molecular tools to provide data on genetic differentiations of tsetse populations, using either mitochondrial or microsatellite DNA markers (Solano et al., 1999, 2000; Krafsur 2003; Marqueze et al., 2004). Cytochrome oxidase1 gene which is important in oxidative activities during metabolism is a maternally inherited gene found in Mitochondrial DNA that could be used to assess genetic drift and bottlenecks in population size (Avise, 1994). It is a conserved gene and relatively stable, whereas Microsatellites are short repetitive nucleotide sequences with conserved flanking regions that could be amplified by polymerase chain reactions (Krafsur and Endsley, 2002). These techniques rapidly identify the levels of epidemiologically important population sub-structuring in tsetse fly vectors.
Investigating genetic variations in natural populations of Glossina species is imperative for ascertaining the success or otherwise of tsetse control programme using SIT. Where there is limited
7
gene flow for instance, SIT may succeed because chances of reinvasion from neighbouring populations may be minimal, but where there is no restriction to gene flow, the success of control campaign using SIT cannot be guaranteed (Krafsur, 2003).
To our knowledge, information on the genetic structures of Nigeria tsetse fly populations that would enable planning of effective control strategies against the vectors in the country is limited. Therefore investigating whether Cytochrome oxidase I mtDNA marker could be used to unravel genetic variations in natural tsetse fly populations could improve our understanding of the dynamics of tsetse fly populations in Nigeria and provide some answers. The result from this study might provide information that could aid choice of effective control strategy against tsetse fly vectors in Nigeria, especially as the country is part of the PATTEC campaign of eradication of economically important Glosssina spp. using a component of SIT.
1.2 Statement of the Research Problem
Despite concerted efforts to control tsetse flies, reinvasion of cleared areas by other tsetse flies often occurs due primarily to inadequate knowledge on the population dynamics of target Glosssina species and their role in disease transmission Ecological data needs to be supported by molecular techniques in providing clearer understanding on the extent of dispersal, delineation of cryptic species boundry, isolation and disease transmission potentials of a given target tsetse population. These are currently limited in Nigeria.
1.3 Justification
Knowledge on the population structure of tsetse flies is of paramount importance as it is expected to allow for the assessment of the menace of tsetse and trypanosomiasis in the country. Information generated from this study may aid the choice of effective anti-tsetse management approaches in the country’s National Parks using a component of the SIT.
8
1.4 Aim and Objectives
1.4.1 Aim
To evaluate and compare the population genetic structures of Glossina species in Nigeria National Parks and Ijah Gwari, with a view to deciphering underlying changes in species composition.
1.4.2 Objectives
i) To determine the species composition and relative abundance of Glossina populations in some Nigeria National Parks and Ijah Gwari.
ii) To determine the apparent densities and distribution patterns of Glossina populations in Nigeria National Parks in relation to vegetation types and climatic conditions
iii) To determine genetic structures of Glossina species in Nigeria National Parks and Ijah Gwari using Cytochrome Oxidase C SU1 (CO1).
iv) To determine the phylogenetic profile/structure of Glossina populations in some Nigeria National Parks and Ijah Gwari.
v) To determine how narrow or wide Glossina populations have drifted in Nigeria National Parks and Ijah Gwari
1.5 Research Questions
i) Is the species composition and relative abundance of Glossina populations in the selected Nigeria National Parks the same?
ii) Are there any variations in the apparent density and distribution patterns in the Glossina populations in relation to vegetation types and climatic conditions in the different National Parks and Ijah Gwari?
9
iii) Are there genetic variations in the different species of Glossina in the different National Parks
iv) Are there variations in the phylogenetic relationship within, among and between the different populations of Glossina spp. in the different National Parks
v) Are the Glossina populations homogenous in the sampled locations?1.0 INTRODUCTION
1.1 Preamble
African Trypanosomiasis is a debilitating tropical disease complex of humans and livestock caused by protozoan parasites of the Genus Trypanosoma. The disease is the major cause of extensive morbidity and mortality in affected individuals and livestock across 38 endemic countries of sub-Saharan Africa (Leak, 1999). It is the major impediment to profitable agriculture and livestock development in the poverty stricken sub-region (Swallow, 2000).
Animal African trypanosomiasis (AAT) otherwise called “nagana” in cattle, is a wasting disease responsible for the death of about three million cattle annually and other breeds of livestock in sub-Saharan Africa (Abenga et al., 2002; Mulumba, 2003). Losses due to AAT alone are estimated at approximately 4.5 billion United States dollars (Hursey, 2001). Large areas of fertile land have been abandoned, and therefore not utilized for agricultural purposes. Animal African trypanosomiasis (AAT) impacts negatively on the socio-economic and political wellbeing of teeming human populations in affected countries (Nash, 1958). The resultant effects of these on large scale is food insecurity, low protein intake, low manure for local organic food production, low income from sale of farm produce, lack of employment and national insecurity (Swallow, 1999).
In Nigeria, losses due to AAT are estimated at about 837.20 million Naira in six states of the Federation (NARP/NITR Mid Term Review, 1998), largely because tsetse and trypanosomiasis have altered the economic health and social status of inhabitants of affected areas in the country. Nigeria, despite its cattle population of over 16 million head (FAO 2004), is the largest importer of meat and dairy products in West Africa (Bonnet et al., 2015).
2
Human African trypanosomiasis (HAT) otherwise called “Sleeping sickness” occurs in an area approximately 1.55 million Km2 with over 70 million people mainly living in rural areas at risk of the disease (Aksoy et al., 2017). The World Health Organisation (WHO) estimates the disease burden at 2.05 million disability adjusted life years (WHO, 2006). Epidemics of sleeping sickness which ravaged sub-Saharan African countries affected by the disease in the twentieth century, caused massive human displacement and depopulation (Steverding, 2008, Simarro et al., 2012). Though the situation was brought under control, in the 1960s, it resurged again in the 1980s (Curtain, 2015), due mainly to economic decline, civil disturbances, war, population movements and refugees (Smith, 1998). The gradual encroachment of people into tsetse infested areas as a result of war, civil disturbances may be responsible for the resurgence of sleeping sickness in areas where the disease had previously been eliminated as observed in the Republic of Congo, Southern Sudan and Rwanda (Lyons, 1992; Arbyn et al., 1995; More and Richer, 2001; Stanghellini and Josenado, 2001; Aksoy et al., 2003; Büscher et al., 2017). However the number of new cases of HAT in 2009 declined to below 10,000 for the first time in 50 years as against 30,000 reported in 1999 and 2804 reported in 2015 (WHO, 2018) due mainly to the improvement of surveillance and treatment activities (Simarro et al., 2011). Even though, with concerted efforts through active surveillance and treatment of infected individuals, the epidemic situation has been brought under control, sleeping sickness still remains endemic in many countries in sub-Saharan Africa, including Nigeria (Franco et al., 2014).
In Nigeria, the disease which was previously regarded as a northern problem and conquered in the 1960s is re-emerging, with a shift to the south of the country (Edeghere et al., 1989; Anere et al., 2006; Curtain, 2008; Adamu et al., 2011). Reports of active surveillance activities have shown that the disease is on the rise even though the WHO has grouped the country amongst those with
3
low sleeping sickness cases (Onyebiguwa et al., 2010; Franco et al., 2014; Karshima et al., 2016; WHO, 2017). In February, 2010, out of 470 subjects screened in Delta State Nigeria, 4 (0.85%) were parasitologically positive and 44 (9.34%) were serologically positive for trypanosomes (NITR unpublished report). In 2011, out of two reported cases (North and South), one was confirmed CATT positive and died (NITR unpublished report).
Trypanosomes are the causative agents of trypanosomiasis. They are single celled protozoan parasites belonging to the genus Trypanosoma. They are transmitted from host to host via the bite of infected blood-sucking insect, tsetse fly (Glossina species). The most economically important trypanosome parasites transmitted in livestock include Trypanosoma vivax, T. congolense, T. brucei, T. simiae, and T. evansi. Two sub-species of T. brucei that are responsible for the disease in humans include T. brucei gambiense, which causes the chronic form of the disease in west and central Africa, and T. brucei rhodesiense that causes the acute form in east and southern Africa where it is a zoonosis. The T. brucei forms that cause the disease in humans and animals are morphologically identical except that the animal parasites are susceptible to a trypanocidal factor due to the presence of a high density lipoprotein associated with the human blood (Rickman and Robson, 1970; Jenni and Brun, 1982; Hager and Hajduk, 1997). The trypanosome parasites that cause trypanosomiasis in both humans and animals are transmitted cyclically by the bites of infected tsetse flies (Glossina species) during blood meals. Other biting flies including tabanus, stomoxys and haematopota have been incriminated in the non-cyclic transmission of the disease in animals (Bitome-Essono, 2015).
Tsetse flies (Glossina species) are obligate haematophagous insects of human and animal hosts occupying about 10 million Km2 (78 %) of the total land mass of the region of sub-Saharan Africa traversing the continent between latitude 14o North and 20o South (Swallow et al., 1998). There
4
are 34 extant species and subspecies of tsetse flies distributed across 38 sub- Saharan African countries (Davies, 1977). Within their confines, tsetse flies are not uniformly distributed, but are distributed discontinuously due to habitat fragmentation (Krafsur, 2009). Added to that is the influence of environmental factors such as temperature, relative humidity, elevation, rainfall and vegetation cover on the relative abundance of the fly populations (Rogers, 1977; Brightwell et al., 1992; Robinson, et al., 1997a; 1997b). The above listed environmental factors in addition to host availability (Rogers and Boreham, 1973; Turner, 1981), cause uneven distribution of tsetse flies between vegetation types. Environmental changes (i.e. land use due to increasing human population and deforestation) have been implicated in the changing pattern of the epidemiology of trypanosomiasis (Van den Bossche et al., 2001; 2010). Tsetse flies exist in geographically isolated units or subpopulations in which flies are adapted to and may be responsible for the observed intraspecific geographical variation in behavior and host preferences (Torr et al., 1988; Colvin and Gibson, 1992).
Out of the 34 extant species and subspecies of tsetse flies so far described, 11 occur in Nigeria covering an area approximately 75-80% of Nigeria’s 928,300 square kilometers total land mass. They are distributed according to habitat preferences between Mangroove swamp vegetation from the coast, through rainforest, derived savanna to Northern guinea /Sahel savannah, between latitude 12-13onorth with extensions along Hadejia-Jama’are hydrographic networks (Davies, 1977; Onyiah et al., 1983). Exceptions include areas above 1,200 meters above sea level (Dede et al., 2005). However, it has recently been observed that tsetse infestations have extended into areas in which they were previously not recorded probably due to the phenomenon of global warming (Jordan, 1989; Kalu, 1996; Aksoy et al., 2003; Dede et al., 2005; Ogedegbe and Rotimi, 2006; Tongue et al., 2015)
5
All the 11 species and subspecies of tsetse in Nigeria are capable of transmitting animal trypanosomiasis, the most important being G. m. submorsitans, G. longipalpis, G. tachinoides and G. p. palpalis (Davies, 1977). Two members of the riverine group, (Glossina palpalis palpalis and Glossina tachinoides), in addition to transmitting animal trypanosomiasis, are able to transmit human trypanosomiasis. It is estimated that if tsetse and trypanosomiasis are eradicated and the area presently occupied by tsetse flies is opened up and put into full utilization, it could support additional 2.5-3.2 times the country’s current estimated livestock population (Onyiah, 1997). In addition, the country could save approximately US $1.3 billion from the importation of meat and dairy products annually, and ensure increased employment opportunities, food availability and national security.
In view of the negative impact of trypanosomiasis on the economy of most countries affected by the disease, the African Heads of State and Government during the 36th Conference of African Union (AU) at Lome, Togo, declared through resolution AHG/Dec.156 (XXXVI), of 12 July, 2000, that tsetse flies be eliminated from the African continent through the Pan Africa Tsetse and Trypanosomiasis Eradication Campaign (PATTEC)
Control of trypanosomiasis relies on the deliberate actions against the trypanosome parasites, the vector and/or the host. The disease could be controlled either by chemotherapy or chemoprophylaxis. However in view of the lack of effective vaccine against the parasites (Nok, 2005), due to the phenomenon of variable surface glycoproteins in trypanosomes (Barry, 1997; Pays et al., 2004), unavailability and high cost of drugs, resistance of parasites to available drugs, vector control is considered the most effective method of trypanosomiasis control (Ravel, 2007). The vector could be controlled by means of aerial or ground application of chemical insecticides, impregnated screens and targets, pour- on formulations used on animals and the use of Sterile
6
Insect Technique (SIT) for mop up operations (Allsop, 2001). However, despite concerted efforts to control tsetse flies, these efforts are hampered by the reinvasion of cleared areas by other tsetse flies (Aksoy, 2003; Krafsur et al., 2008; Beadell et al., 2010). The limiting factors have mainly been attributed to inadequate knowledge on the dynamics of fly populations. Invariably, adequate knowledge on the population dynamics of tsetse flies is key to successful control of tsetse flies using the Sterile Insect Technique (Feldmann et al., 2005; Hendrichs, et al., 2005; Torr et al., 2006).
Earlier laboratory studies had shown that tsetse populations could be differentiated (Van Etten, 1981; 1982a; 1982b; Torr et al., 1988; Colvin and Gibson, 1992; Moloo, 1992, 1993), but genetic basis of the differences were never investigated probably due to limited availability of molecular tools. With the current availability of molecular tools, studies have shown that the genetic basis of differentiations in tsetse populations could be investigated. It is possible for instance to employ molecular tools to provide data on genetic differentiations of tsetse populations, using either mitochondrial or microsatellite DNA markers (Solano et al., 1999, 2000; Krafsur 2003; Marqueze et al., 2004). Cytochrome oxidase1 gene which is important in oxidative activities during metabolism is a maternally inherited gene found in Mitochondrial DNA that could be used to assess genetic drift and bottlenecks in population size (Avise, 1994). It is a conserved gene and relatively stable, whereas Microsatellites are short repetitive nucleotide sequences with conserved flanking regions that could be amplified by polymerase chain reactions (Krafsur and Endsley, 2002). These techniques rapidly identify the levels of epidemiologically important population sub-structuring in tsetse fly vectors.
Investigating genetic variations in natural populations of Glossina species is imperative for ascertaining the success or otherwise of tsetse control programme using SIT. Where there is limited
7
gene flow for instance, SIT may succeed because chances of reinvasion from neighbouring populations may be minimal, but where there is no restriction to gene flow, the success of control campaign using SIT cannot be guaranteed (Krafsur, 2003).
To our knowledge, information on the genetic structures of Nigeria tsetse fly populations that would enable planning of effective control strategies against the vectors in the country is limited. Therefore investigating whether Cytochrome oxidase I mtDNA marker could be used to unravel genetic variations in natural tsetse fly populations could improve our understanding of the dynamics of tsetse fly populations in Nigeria and provide some answers. The result from this study might provide information that could aid choice of effective control strategy against tsetse fly vectors in Nigeria, especially as the country is part of the PATTEC campaign of eradication of economically important Glosssina spp. using a component of SIT.
1.2 Statement of the Research Problem
Despite concerted efforts to control tsetse flies, reinvasion of cleared areas by other tsetse flies often occurs due primarily to inadequate knowledge on the population dynamics of target Glosssina species and their role in disease transmission Ecological data needs to be supported by molecular techniques in providing clearer understanding on the extent of dispersal, delineation of cryptic species boundry, isolation and disease transmission potentials of a given target tsetse population. These are currently limited in Nigeria.
1.3 Justification
Knowledge on the population structure of tsetse flies is of paramount importance as it is expected to allow for the assessment of the menace of tsetse and trypanosomiasis in the country. Information generated from this study may aid the choice of effective anti-tsetse management approaches in the country’s National Parks using a component of the SIT.
8
1.4 Aim and Objectives
1.4.1 Aim
To evaluate and compare the population genetic structures of Glossina species in Nigeria National Parks and Ijah Gwari, with a view to deciphering underlying changes in species composition.
1.4.2 Objectives
i) To determine the species composition and relative abundance of Glossina populations in some Nigeria National Parks and Ijah Gwari.
ii) To determine the apparent densities and distribution patterns of Glossina populations in Nigeria National Parks in relation to vegetation types and climatic conditions
iii) To determine genetic structures of Glossina species in Nigeria National Parks and Ijah Gwari using Cytochrome Oxidase C SU1 (CO1).
iv) To determine the phylogenetic profile/structure of Glossina populations in some Nigeria National Parks and Ijah Gwari.
v) To determine how narrow or wide Glossina populations have drifted in Nigeria National Parks and Ijah Gwari
1.5 Research Questions
i) Is the species composition and relative abundance of Glossina populations in the selected Nigeria National Parks the same?
ii) Are there any variations in the apparent density and distribution patterns in the Glossina populations in relation to vegetation types and climatic conditions in the different National Parks and Ijah Gwari?
9
iii) Are there genetic variations in the different species of Glossina in the different National Parks
iv) Are there variations in the phylogenetic relationship within, among and between the different populations of Glossina spp. in the different National Parks
v) Are the Glossina populations homogenous in the sampled locations?

 

GET THE COMPLETE PROJECT»
Do you need help? Talk to us right now: (+234) 08060082010, 08107932631, 08157509410 (Call/WhatsApp). Email: edustoreng@gmail.com