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ABSTRACT

 

Study on epidemiology and transmission patterns of Schistosoma haematobium infections were
carried out between July, 2013 and April, 2014 in 16 out of 47 communities making up Ebonyi
Central zone Ebonyi State, Nigeria. This is to determine the prevalence of Schistosoma
haematobium infection and its transmission patterns among the inhabitants of Ebonyi Central
senatorial zone. Centrifugation method was employed to determine intensity of Schistosoma
haematobium eggs in 10ml of urine. An overall prevalence of 19.0% (n = 342) was observed
among the 1800 people examined. Infection was recorded in all the communities in the study
area with Enyibichiri community (32.2%) recording the highest prevalence followed by
Umuoghara community (25.5%) while Oshugbu community with 6.6% had the least prevalence.
Across communities, the prevalence of Schistosoma haematobium infection differed significantly
. More males 225(20.3%) than females 117(16.9%) were significantly infected in all the
communities with haematuria as the predominate presenting symptoms. Infection prevalence was
significantly higher (27.3%) among the age group 11 – 20 years. Statistical analysis revealed
that the prevalence and intensity were significantly (P< 0.05) more among 11 – 20 years age
group. In the moderate infection, those 11 – 20 years had significantly high intensity when
compared with those of other age groups while peak intensity was recorded among 11 – 20 age
group. Intensity of light and moderate infections varied significantly (P<0.05). Intensity of heavy
infection in the different age groups was not significantly different (P>0.05). Highest prevalence
of haematuria (62.3%; n=86) was recorded in the age group 11 – 20 years old while the least
prevalence was recorded among group 31 – 40 years. Prevalence of haematuria differed
significantly among different age groups (P<0.05). Famers had the highest infection rate (35.4%;
n=149), followed by students/pupils (21.2%; n=117), civil servants (9.7%; n=38), traders (9.1%;
n=23) and artisans (8.2%, n=15). Chi-square analysis showed a very highly significant difference
among the occupational groups (P<0.05). Generally, human water contact activities in the study
area revealed a marked seasonal variation in both the frequency and duration of water contacts.
More contacts were observed in the dry season than in the rainy season. A cross-sectional study
on the sex and age-specific water contact activities among various water sites showed that the
frequency and duration of contact males made with water were significantly more than females
(P<0.05). Bulinus globosus was incriminated as a major snail host of Schistosoma haematobium.
Snail population increased during the rainfall but snail infection was higher in the drier months.
Of the 48 Bulinus globosus collected, 11(22.9%) were infected or found to shed cercaria. Report
from this study showed that the school children, teenagers and young adults are the population at
risk of schistosomiasis infection and it will provide a guide for the treatment of community
members and help in eradicating schistosomiasis infection in the study area. There is urgent need
for a decisive control intervention which should by mass chemotherapy and focal application of
molluscicides in the water bodies during the dry season.

 

TABLE OF CONTENTS

Title page – – – – – – – – – – i
Certification – – – – – – – – – – ii
Dedication – – – – – – – – – – iii
Acknowledgement – – – – – – – – – iv
Abstract- – – – – – – – – – – v
Table of content – – – – – – – – – vi
List of tables – – – – – – – – – – viii
List of figures – – – – – – – – – – ix
List of appendices – – – – – – – – – x
CHAPTER ONE: INTRODUCTION
1.1 Background of the Study – – – – – – – 1
1.1.1 Justification of the study – – – – – – – 5
1.1.2 Objectives of the study – – – – – – – 5
1.2 Literature Review – – – – – – – – 6
1.2.1 Life cycle of Schistosoma haematobium – – – – – 7
1.2.2 Epidemiology of Schistosoma haematobium infection – – – 11
1.2.3 Transmission of urinary schistosomiasis – – – – – 12
1.2.4 Persistence, latency and natural history of urinary schistosomiasis – – 13
1.2.5 Snail intermediate host – – – – – – – 14
1.2.6 Reservoir host (Non-human) – – – – – – – 16
1.2.7 Cancer of the urinary bladder – – – – – – – 17
1.2.8 Cancer of the female genital tract – – – – – – 19
1.2.9 Effects of Schistosoma haematobium infection on detoxifying enzymes – 19
1.2.10 Symptoms of urinary schistosomiasis- – – – – – 20
1.2.11 Diagnosis – – – – – – – – – 21
1.2.12 Pathological effects of urinary schistosomiasis – – – – 24
1.2.13 Prevention/Control – – – – – – – – 25
1.2.14 Treatment of urinary schistosomiasis – – – – – – 28
vii
CHAPTER TWO: MATERIALS AND METHODS
2.1 Study Area – – – – – – – – – 30
2.1.1 Selection of communities – – – – – – – 31
2.1.2 Ethical clearance – – – – – – – – 34
2.1.3 Study design – – – – – – – – – 34
2.1.4 Sample size – – – – – – – – – 34
2.1.5 Human water contact studies – – – – – – – 35
2.1.6 Urine Sample collection – – – – – – – 38
2.1.7 Laboratory analysis – – – – – – – – 40
2.1.8 Malacological survey – – – – – – – – 41
2.1.9 Data analysis – – – – – – – – – 42
CHAPTER THREE: RESULTS
3.1 Prevalence of Schistosoma haematobium Infection – – – – 43
3.1.1 Prevalence of infection in the study communities – – – – 43
3.1.2 Prevalence of urinary schistosomiasis in relation to sex – – – 45
3.1.3 Prevalence of infection in relation to age group – – – – 47
3.1.4 Prevalence of infection in relation to age and sex – – – – 50
3.1.5 Intensity of infection in relation to age- – – – – – 52
3.1.6 Haematuria in relation to age – – – – – – – 59
3.1.7 Prevalence of infection in relation to occupation – – – – 62
3.1.8 Human water contact studies – – – – – – – 64
3.1.9 Variation in human water contact among water sites – – – – 66
3.1.10 Variation of contact behaviour by age and sex – – – – 68
3.1.11 Prevalence of infection in relation to water contact activities – – – 70
3.1.12 Water contact in relation to sex – – – – – – 72
3.1.13 Monthly variation in water contact pattern – – – – – 74
3.1.14 Snail vector investigation – – – – – – – 76
CHAPTER FOUR: DISCUSSION
Conclusion/Recommendations – – – – – – – 85
References – – – – – – – – – – 87

 

 

CHAPTER ONE

INTRODUCTION
1.1 Background of the Study
Schistosomiasis also known as Bilharziasis is a parasitic disease caused by infection from one of
species of parasitic trematodes (Flukes) of the genus Schistosoma (Noble and Glem, 1982). The
worm was discovered by Theodore Bilharz (a German pathologist) while performing autopsy in
Cairo-Egypt. The name Schistosoma was coined by Weinland to reflect its shape which is a cleft
(Shisto) and body (Soma). The disease is now commonly known as schistosomiasis or
Bilharziasis as suggested by Jordan and Webbe (1993). It is one of the most common parasitic
infections in the world (Gracio et al., 1992) particularly in sub-Saharan Africa, ranking second
only to malaria in terms of its social-economic and public health importance in tropical and subtropical
areas (Ogbe, 2002).
It has been estimated that schistosomiasis occurs in 77 countries of Africa, Middle East, India,
South and Central America and that more than 237 million people in tropical and sub-tropical
regions are infected by the disease (World Health Organization, WHO, 2012; Huw et al., 2004;
Chitsulo et al., 2000). Schistosoma belongs to the class Trematoda, phylum Platyhelminthes,
order Strigeatoidea and family Schistosomatoidae. Ten species of Schistosoma are known but the
main prevalent species affecting humans are Schistosoma haematobium, Schistosoma mansoni,
S. intercalatum, S. japonicum and S. mekongi (Ivoke et al., 2014). Other Schistosoma species of
parasitological importance include; Schistosoma bovis, S. mathei, S. hippopotami, S. sprinadalis,
S. rhhaini, some of these have also been reported in man (Noble and Glem, 1982). Of all people
suffering from schistosomiasis, 85% live in sub-Saharan Africa where S. haematobium, S.
mansoni and S. intercalatum are endemic (Chitsulo et al., 2000; Lengeler et al., 2002). These
2
flukes have certain features in common; they are dioecious, that is their sexes are separate and
they exhibit sexual dimorphism. The thicker male carries the slender female in a groove called
gynaecophoric canal (Okafor, 1990a). They have aquatic snails of various genera as their
intermediate hosts. The distribution of the snails coincides with the geographical distribution of
the diseases (Ugbomoiko, 2000). Man serves as the definitive host of S. haematobium, S.
mansoni, S. intercalatum, while S. japonicum parasitizes many animals as well as humans.
Schistosomiasis can be divided into intestinal schistosomiasis caused by four species namely; S.
japonicum, S. mansoni, S. intercalatum and S. mekongi, the next one is urinary schistosomiasis
caused by Schistosoma haematobium. Among the species of Schistosoma, Schistosoma
haematobium is the most widely spread (Steinmann et al., 2006; Van der Werf et al., 2003).
Schistosoma haematobium which causes urinary schistosomiasis is noted to be more prevalent in
Nigeria than intestinal schistosomiasis due to the wider distribution of its snail host, Bulinus
species (Ejezie, 1991; Ugbomoiko, 2000). This is in addition to indiscriminate passing of urine
containing Schistosoma haematobium eggs into water supplies containing the snail intermediate
host. Knowledge of patterns of exposure to infection is essential understanding of the
epidemiology of Schistosoma haematobium infection.Transmission of Schistosoma haematobium
is focal and usually depends on the presence of a compatible snail intermediate host of the
parasite and human contact with the infected water (Agi and Okafor, 2005). The purpose of
human water contact studies is to observe who in a study population visits natural water bodies,
the purpose of visits, the site of contacts, when and duration of contact and finally the type of
exposure (Jordan and Webbe, 1993)
Urinary schistosomiasis occurs in all the states of Nigeria with a high infection rate among
school age children between the age of 6 and 17 years usually presenting with the highest
3
prevalence and intensity of Schistosoma haematobium infection (Okoli and Odaibo, 1999; WHO,
2002). In urinary schistosomiasis, there is risk of haematuria that is blood in urine, dysuria that is
painful urination, bladder cancer or kidney failure, nutritional deficiencies and growth
retardation in children (Nokes et al., 1999; Mostafa et al., 1999). It is also the most prevalent of
the water-borne infections and one of the greatest risks to health in rural areas of developing
countries. Many factors enhance the prevalence and intensity of infection (Nnoruka, 2000), these
include presence of appropriate snail host, socio-economic status of vulnerable populations,
water supply and sanitation patterns as well as migration patterns. There are various socioepidemiological
factors which are also responsible for the transmission of the disease and level
of infection. Among such factors are the distance from transmission site, migration and
emergence of new foci, urbanization, socio-economic status, poor sanitation and contamination
of water source (Nnoruka, 2000). People at high risk of infection are those involved in fishing
activities, immigration, farming, bathing, paddling and swimming in cercaria infested water
bodies (Ivoke et al., 2014).
Among the few studies on human water contact patterns in tropical Africa are those by Dalton
and Pole (1978) in Lake Volta, Ghana (Tayo et al., 1980). The activities of women and children
which involve washing of house – hold utensils and fetching of water in the morning or evening
also take them to water sites. These activities are seen to enhance transmission (Ukoli, 1990).
School – aged children are mostly infected with this silent destructive disease, especially in male
than female because of their play habits (Ekejindu et al., 2002). Schistosoma haematobium
transmission starts when infected person urinates directly into water bodies, thereby introducing
eggs which hatch into miracidia that infect snail hosts (Ekwunife, 2003). Inside the snail, the
miracidia develop into infective stages called cercariae which are released into the water to infect
4
man, definitive host. This can only be controlled by the provision of urinaries, introduction of
effective sewage disposal systems, and provision of treated swimming pools for recreational
activities (Gracio et al., 1992), wearing of foot wear to protect the legs against active penetration
by the cercariae of the Schistosoma (Amali, 1989).
In Nigeria, the national policy on schistosomiasis control adopted praziquentel as the main drug
of choice in the control strategy aimed at reducing morbidity (Oniya and Jeje, 2010). However, it
was not until recently that an assessment was made on different channels for praziquantel
delivery in mass treatment effort. Unfortunately not much has been achieved in the control of
urinary schistosomiasis in the country largely because the disease is mainly a rural occupation
disease that affects people engage in agricultural activities and other people residing in rural and
semi-rural areas (Mafe et al., 2000; Okpala, et al., 2004). There is high level risk of people
becoming infected as a result of low literacy level, poverty, sub-standard hygiene and inadequate
public infrastructures (Engels et al., 2002). Schistosoma haematobium as one of the helminth
parasites is classified according to Smith et al. (1968) as follows:
Kingdom —————————————————— Animalia
Sub-kingdom ————————————————- Metazoa
Phylum ——————————————————– Platyhelminthes
Class ———————————————————– Trematoda
Sub-class —————————————————— Digenea
Order ———————————————————- Strigeatoidea
Sub-order —————————————————– Strigeata
Super-family ———————————————— Schistosomatoidae
Family —————————————————— Schistosomatoidae
Genus ——————————————————-Schistosoma
Species——————————————————-Schistosoma haematobium
5
1.1.1 Justification of the study
The justifications that necessitated this research are as follows:
Ø The choice of the zone was based on reports from general hospitals, clinics, and medical
health centres about cases of urinary schistosomiasis in the area especially among
primary school children. Despite these reported cases of urinary schistosomiasis in
central Ebonyi state, no investigation or research was carried out in the area to find out
the transmission patterns, prevalence and intensity of this infection among the
inhabitants.
Ø The communal life in central zone of Ebonyi state is such that domestic activities like
washing of clothes and utensils and fetching of water are the sole responsibility of the
school age children who are the most susceptible age group to Schistosoma haematobium
infection.
Ø The climate of Central Ebonyi state is tropical and the vegetation characteristics are
predominantly the Guinea savannah which makes the people in the area susceptible to
urinary schistosomiasis transmission in line with Ivoke et al. (2014) who stated that
schistosomiasis remains one of the major health problems in tropical and sub-tropical
countries with school age children usually the most affected.
1.1.2 Objectives of the study
The principle objective is to ascertain the epidemiology and transmission patterns of Schistosoma
haematobium infection in Central Ebonyi State, Nigeria.
Other objectives of this study are to:
i Determine the prevalence and intensity of Schistosoma haematobium infection among
inhabitants of Ebonyi Central senatorial zone.
6
ii Determine types of water-contact activities in the study communities in relation to
Schistosoma haematobium transmission.
iii Identify the intermediate hosts of Schistosoma haematobium at the water-contact sites.
1.2 Literature Review
Schistosomiasis is an infection caused by blood flukes (trematodes) of the genus-Schistosoma. It
is among the wide spread parasitic diseases of tropical and sub-tropical countries of Africa, Asia
and South America (Emejulu, et al., 1992; Eyo et al., 2012).
WHO (1985) made a first attempt to compile the existing knowledge about the consequences and
the resulting public health importance of schistosomiasis. The report outlined a classification of
the causes of the disease by Schistosoma species and pointed to the morphology that could be
applied in clinical and community-based studies. It also stressed the need to assess public health
importance beyond death, disability and disease, including loss of income and production costs
as targets for future investigations (WHO, 1991).
According to Dennis et al. (1993), schistosomiasis changes the distribution of income among
workers. Recent intervention studies, which consider the infection load (intensity) as well as
spectrum of concomitant disease, provided some evidence of how schistosomiasis especially
urinary schistosomiasis can impair the growth and well being of children ( Ivoke et al., 2014).
Stephenson et al. (1985) reviewed the relation of schistosomiasis to nutritional status and noted
the methodological difficulties encountered when measuring any sustained impact on nutritional
parameters, physical fitness and mental ability.
Urinary schistosomiasis is a rural disease associated with activities related to water use, such as
farming, fishing, bathing and recreation, washing cloths and kitchen utensils as well as personal
hygiene. Other factors include spread of snails by floods, distance from transmission site,
7
migration and emergence of new foci, socio-economic status, sanitation, water supply patterns
and level of contamination of water source by infected urine, large scale movement of labour
forces, urbanization, spread of animal reservoir hosts and inadequate control measures
(Strickland, 1991; WHO, 1993; Ivoke et al., 2014).
The differences in infection with respect to age and sex depend on the frequency of water contact
and the contact varies with seasons. It was noted that transmission potential was high (99.69%)
in the dry season and low (4.61%) in the wet season in flowing water (Arene et al.,1989). On the
contrary, the transmission potential was low (0.3%) in stagnant water habitats during the dry
seasons and high (95.99%) during the wet season (Mafe, 1997). Adewummi et al. (1990) also
noted a seasonality of transmission of Schistosoma haematobium infection in South – western
Nigeria.
1.2.1 Life cycle of Schistosoma haematobium
Gryseels et al. (2006) noted that Schistosoma haematobium has a complex life cycle, which takes
place in humans, and in an intermediate host of a fresh water snail. The schistosome’s life cycle
is a cycle from humans to water to snail to water and back to human (Ekwunife, 2003). The
spined eggs are laid by females at intervals in batches of 5 to 40, each batch being endorsed in a
mass of jelly-like material. The eggs leave the human body with urine and faeces depending on
the species and enter into fresh water (Figure 1). Hatching depends on temperature, light and
osmotic pressure (WHO, 2007).
Eggs of schistosoma are differently spined. Eggs of Schistosoma haematobium and Schistosoma
intercalatum have terminal spine while that of Schistosoma japonicum and Schistosoma masoni
have minute spines or tubercules (Ivoke, 2009). Embryonated eggs secrete proteolytic enzymes
that help the eggs to enter the surrounding connective tissue, collect in submucosa before
8
entering the lumen of either small intestine or bladder as the case may be. Not all the eggs are
passed out through the bladder with urine, many of them are swept back to the liver where they
are trapped and form liver granuloma (Anosike et al., 1992). In fresh water, the eggs hatch into
ciliated miracidia which swim about until they find suitable intermediate host (Ekejindu et al.,
2002). The miracidia die within 24 hours if they do not find a suitable intermediate host (Okafor,
1990b). To increase the chance of locating the host, the miracidium has a negative geotactic and
positive photoactive behavioural response, which tend to place it in the general environment of
the snail host. Chemical attraction from the snail such as mucus, long chain fatty acids and even
amino acids attract the miracidium (Ofoezie, 1999).
After the miracidium makes contact with the snail, there is a period of exploratory behaviour
prior to penetration (Ivoke et al., 2014). Penetration sites include foot of the snail, the tentacle
and edge of the mantle. Penetration is the combination of mechanical motion of the apical
papillae and histolytic secretion released from the penetration glands (Ivoke et al., 2014). In the
snail intermediate host, miracidium gives rise to mother sporocyst which produces daughter
sporocysts. The daughter sporocyst migrates to the digestive gland of the snail and produces the
next infective stage, the cercariae with bifurcated tail. (Ekejindu et al., 2002). The mean cercaria
output has been estimated to be about 1500 per day, and this lasts for up to about 18 days. It
takes about 4 weeks for an infected snail to start releasing cercaria.
The cercaria are released on cercadian rhythm (24 hours cycle) during day light hours. The
cercaria are very active, non-feeding stages which rely only on stored glycogen food reserves
(Okoli and Iwuala, 2004). The forked tail cercaria (forcocercous cercariae) can live for up to 48
hours outside the snail (Cheesbrough, 2002). Host location occurs partly through the use of water
turbulence and skin-derived chemicals released from the skin of the human host. Host infestation
9
is by penetration only (Ivoke et al., 2014). Penetration occurs in three phases; attachment to the
legs, exploratory behaviour and penetration into the epidermis. After penetration, the cercaria
loses its tail to form a schistosomulum (Utzinger et al., 2001).
The schistosome masks itself with nodules which help it to escape the host immune system.
Schistosoma haematobium remain in the dermis for about 2 days and proceed to the lungs where
they stay and double the size. The lung phase last for 3-8 days and the parasites move to the liver
sinusoids where they mature to adult within 28-35 days post infection (Abubakar et al., 2006).
Paired adults enter the veins of bladder where the females start laying eggs (Figure 1). The males
and females remain in close association with the female lying in the gynaecophoric canal of the
male receiving products such as glucose from the male (Ivoke et al., 2014). Adult worms can
survive in the host for 20 – 30 years.
10
Figure 1: The life cycle of Schistosoma haematobium
Source: (Taina, 2001).
11
1.2.2 Epidemiology of Schistosoma haematobium infection
Schistosoma haematobium is endemic in over 77 countries of Africa and the Middle East (WHO,
2012). It is also occasionally seen in Western Asia. The World Health Organization considers it
a significant health problem in much of Africa. WHO (2012) estimated that worldwide, 237
million people are infected with the parasite most of them live in sub-Saharan Africa. Roughly
70 million persons suffer from hydronephrosis (an accumulation of urine in the kidney due to
obstruction of the urethra) (Poggensee and Feldmeir, 2001). It was estimated that 150,000 people
die each year from resultant renal failure and unknown but significant number from bladder and
other genitor urinary cancers. The overall mortality rate is estimated to be least 2 per 1,000
infected patients per year (WHO, 2002).
In many places, there is high incidence of infection in young boys and women, this occurs
because of increased contact with water (compared to other population groups in culture) when
typically fetching water for household use, young boys often play in or near water. In some
regions where men are primarily fresh water fisher men or farmers using irrigation, they have
higher rates of schistosomiasis (Capron et al., 2002). So its spread is mostly seen among poor
populations especially in developing countries who have limited access to proper health care,
less effective prevention measures and to live in environmental conditions that favour
transmission. Tourism, migration and incidence of refugees have contributed to more and more
cases in developed- non endemic countries (Sam-Wobo et al., 2008).
Human behavioural and cultural practices as well as the socio-economic condition of the
epidemiology of the disease, effects of ecological and parasitological factors have contributed to
the more incidence of urinary schistosomiasis (Ukoli, 1990). The presence of natural fresh water
bodies in which the right species of the snail host thrives will aid in the transmission of the
12
disease. Man becomes infected by contact with contaminated water bodies during his daily
activities (WHO, 1998). Human contact with water bodies arises from four major basic needs
namely: occupational, recreational, domestic and socio-cultural activities. Water contact
activities are usually encountered more in children which place them at a higher risk of getting
infected with the disease. Doudier et al. (2004) examined the relationship between water contact
and infection in Zuru emirate of Kebbi State and recorded a high prevalence rate of 94.3% due to
swimming. So, swimming is also an important factor of transmission with regards to sex.
Ekejindu et al. (2002) reported that prevalence and intensity of infection is significantly higher in
males than in females even through both males and females are exposed to the same water
bodies. High prevalence in male is due to prolonged swimming than females who may be
processing their food outside the water body.
Pollution of water bodies with human excreta and urine thereby providing a source of infection
for the snail intermediate host is one of the most important factors in the epidemiology of
schistosomiasis (Ukoli, 1990). Some of the epidemiological factors as observed by Okanla et al.
(2003) showed that children of salaried workers exhibited less prevalence rate of 22.4% than
children of farmers and fisher men with 49.3%. Another important factor in the transmission of
the disease is the physiochemical characteristics of water bodies. Nnoruka et al. (2002)
established that a pH range of 6.5 – 9.0 for surface water favours the breeding of fresh water fish,
which can attract fishermen thus sustaining a high level of water contact.
1.2.3 Transmission of urinary schistosomiasis
Transmission patterns of urinary schistosomiasis occurs in stagnant or slow moving fresh water
bodies using snails as the intermediate host particularly the Bulinus species (Okafor, 1990b;
Emejulu et al., 1992). Transmission requires contact between the definitive host and water
13
containing the snail intermediate host, which relate to the rate of exposure and other factors such
as area of skin exposure, the rate of contamination, the degree to which the activity undertaken is
associated with urination or defecation, the time of day (cercaria emergency has z marked
diurnal rhythm) and direct exposure to water bodies e.g. fishermen, farmers working in irrigation
canals, women fetching water for home use (Ivoke et al., 2014).
Other socio-epidemiological factors responsible for transmission are distance from transmission
site, migration and emergence of new foci, urbanization, socio-economic status, sanitation, water
supply patterns and level of urination into source (Tanner, 1989). Many other host-related and
environmental risk factors have been identified that may affect the risk of acquiring schistosome
infection, and /or influence the distribution, prevalence, intensity of infection, morbidity and
mortality of schistosomiasis (Quinnell, 2003). Among these are genetic factors such as
behaviour, household works, climate immune response of the host and concomitant infections
e.g. hepatitis (Bethony et al., 2004).
1.2.4 Persistence, latency and natural history of urinary schistosomiasis
a. Persistence
Schistosome worms do not multiply in the host. The infection status is the result of an
accumulation of consecutive infections, where individuals with the most intense infections
usually have a higher risk of developing morbidity (Gryseels et al., 2006). In the absence of reinfection,
the infection subsides when the schistosome worn dies, which is usually after 3-5
years. However, in endemic areas with continuous exposures, re-infection is the rule rather than
the exception (Nmorsi et al., 2007).
In highly endemic areas, children start to accumulate worms as soon as they are old enough to
have contact with water and may, because of the chronic nature of the infection and continued
14
susceptibility to re-infection, remain infected throughout their lives (Ejezie et al., 1989). The
possibility that adults might develop immunity to schistosome infection was initially suggested
based on the shape of the age intensity curve in endemic communities, which characteristically
shows a rise in intensity during the first two decades of life, followed by a decline in adults to
very low levels (Butterworth, 1998). Indeed, numerous studies have provided epidemiological
and clinical evidence that people living in endemic areas acquire some form of protective
immunity after years of exposure. However, age related innate resistance mechanisms may also
play an important part in the epidemiology of schistosomiasis (Butterworth, 1993; Gryseels et
al., 2006).
b. Latency and Natural History
Not much is known about the latency between the onset of infection and the appearance of
cancer, or about the steps that might lead to cancer. Infection with Schistosoma haematobium is
not synonymous with clinical disease, and many infections are asymptomatic (Tayo et al., 1980).
Of those infected, a small proportion develops serious chronic disease, after varying duration of
exposure and infection (Vennervald and Dunne, 2004). Mostafa et al. (1999 ) noted that the
incidence of bilharzias bladder cancer in various African countries peaks between the ages of 40-
49 years, while infection with Schistosoma haematobium begins in childhood (as early as 6
months of age), and peaks usually in the second decade of life (between the ages of 5-15 years).
This would imply a latency period of 20-30 years.
1.2.5 Snail intermediate host
Most snail intermediate hosts of human Schistosoma species belong to three genera,
Biomphalaria, Bulinus and Oncomelania (Udonsi, 1990). They are fresh water pulmonate snails,
non-operculate, hermaphrodites, with lungs and haemoglobin in their blood, which gives them a
15
characteristics pink or red colour (WHO, 1993). The shape of the outer shell can be used to
identify the species involved. The sub-family Bulininae (family Planorbidae and class
Gastropoda) contains the major intermediate hosts for Schistosoma haematobium and
Schistosoma intercalatum in Africa and Eastern Mediterranean and they are distinguishable by
their ovate shells (Chitsulo et al., 2000). The Bulinus species are: Bulinus globosus, Bulinus
truncatus, Bulinus forskali, Bulinus africanus, Bulinus nasutus and Bulinus productus (Anosike
et al., 2001; Ugbomoiko, 2000).
All species of Bulinus and Biomphalaria are hermaphrodites and are capable of self or cross
fertilization. The specie Biomphalaria is the intermediate host for Schistosoma mansoni in Africa
and the America, and is characterised by disk or lens-shaped shells (Okafor, 1990a; Emejulu et
al., 1992). The amphibious snail intermediate host of Schistosoma japonicum is Oncomelania
hupensis in South-east Asia; it is unisexual, has gills instead of lungs and is operculate with
conical or turniculate shell that is adapted to live on land but tends to be confined to stable
marshy habitats with constant high humidity (Strickland, 1991; Abdel-wahab, 1980).The snail
host for Schistosoma mekongi is Tricula aperta (Cowper, 1971)
Generally, the aquatic snail hosts of schistosomes occur in shallow water near the shores of
lakes, ponds, marshes, streams and irrigation channels (Ukoli, 1990). So, their habitats include
almost all types of fresh water body ranging from small temporary ponds and streams to large
lakes and rivers. They live on water plants and mud that is rich in decaying organic matter (Tayo
et al., 1980). They can also be found on rocks, stones or concrete covered with algae or on
various types of debris. They are most common in waters where plants are abundant and in water
moderately polluted with organic matter, such as faeces and urine as is often the case near human
habitations (WHO, 2002). Plants serve as substrates for feeding and oviposition as well as
16
providing protection from high water velocities and predators, such as fish and birds (Ogbe,
2002). The aquatic snails that transmit Schistosoma haematobium and Schistosoma mansoni
may be found in flowing water, whereas the amphibious intermediate host of Schistosoma
japonicum spends much of its time out of water, preferring moist soil at the edge of slow-flowing
streams or irrigation canals (Mafe et al., 2000). Within its habitat, snail distribution may be
patchy and detection requires examination of different sites. The infective dynamics of the
intermediate hosts are such that low percentages of snail (e.g. 0.2 to 2%) are infected at any one
time in an area highly endemic for schistosomiasis (Oladejo and Ofoezie, 2006). Even though a
single snail may shed thousands of cercariae, the number detectable in an infested body of water
is astonishingly small. Again snail cercarial shedding is seasonal in many areas. Snail densities
vary significantly with the season, hence Okafor (1990a) noted that the transmission potential
was low (0.3%) in stagnant water habitat during the dry season and high (95.99%) during the wet
season. Adewunmi et al. (1990) reported the seasonality of transmission in South Western
Nigeria.
Consequently, the streams and other natural or man-made water sources, such as well, rivers and
ponds that constitute major sources of domestic water supply, serve as habitats for the snail
intermediate hosts, and extensive use of these water sources, especially for swimming, bathing,
washing clothes, increase the chances for man-Schistosoma cercariae contact (Dalton and Pole,
1978; Ivoke et al., 2014).
1.2.6 Reservoir host (Non-human)
Various species of animals are found naturally infected with various Schistosoma species that
infect humans (Bruce, 1990). Dogs, rats, cattle, pigs, sheep are important in the continuing of
human infection with Schistosoma japonicum, certain primates are found naturally infected with
17
Schistosoma haematobium, while rodents are found to be probably reservoir hosts and might be
expected to be capable hosts of Trichobilharzia ocellata. Trichobilharzia szidati is the bird
schistosomes (Bruce, 1990).
1.2.7 Cancer of the urinary bladder
A substantial number of descriptive studies from Africa have shown that, the estimated incidence
of urinary bladder cancer was higher in areas with high prevalence of Schistosoma haematobium
infection than in areas with a low prevalence (International Agency for Research on Cancer,
1994). The estimated incidence of urinary bladder cancer was related to the proportion of
cancerous urinary bladder specimens containing Schistosoma haematobium eggs or egg remnants
(Ivoke et al., 2014; Mostafa et al., 1999). The sex ratio of urinary bladder cancer cases varied
widely and corresponded to the relative involvement of men and women in agricultural work (a
risk factor for Schistosoma haematobium infection); and squamous cell cancers of the urinary
bladder were proportionately more common in populations with a high prevalence of
Schistosoma haematobium infection than in areas without these characteristics (Smith et al.,
1968).
A large number of case series and case report have repeatedly emphasized the prevalence of
squamous cell urinary bladder tumours among patients with evidence of Schistosoma infection.
Clinically, the most notable and constant feature described was the relatively young age of the
cases that had evidence of a link to Schistosoma haematobium infection (International Agency
for Research on Cancer, 1994). A descriptive study by Groeneveld et al. (1996) on the incidence
of different historical types of bladder cancer in various racial groups living within the same
geographical area of Kwazulu-Natal, South Africa, reported similar results. Squamous cell
carcinoma occurred in 53% of the African patients (who have, according to the authors, a much
18
higher risk of exposure and infestation to Schistosoma haematobium due to socio-economic,
cultural and educational factors), and in 2% of the Caucasian patients (Stephenson et al., 1985).
More eggs of Schistosoma haematobium were seen in microscopic sections of the bladder
tumour in 85% of the patients with squamous cell carcinoma, and in 10% of the patients with
transitional cell carcinoma, the working group noted that no mention is made of the percentages
of Schistosoma haematobium ova in microscopic sections of Africa patients with bladder cancer
of the squamous-cell-carcinoma type (International Agency for Research on Cancer, 1994).
The mean age at presentation of African patients was at least 20 years younger than that of
caucasian patients. Study from Egypt (Poggensee and Feldmeier, 2001), found that the odds ratio
(OR) for urinary schistosomiasis was higher in subjects who were younger at first diagnosis (OR,
3.3 for < 15 yrs), and with a long time since first diagnosis (OR, 3.0 for ≥ 35yrs), suggesting a
duration-risk relationship and a long term effect of urinary schistosomiasis on bladder cancer
(Poggensee and Feldmeier, 2001). In contrast to some of the earlier case-control studies, all
studies after 1994 considered possible confounding by age, sex and smoking. In one study that
considered tobacco smoking as a confounding factor (Parkin et al., 1994), no significant effect
was observed due to tobacco smoking (OR,1.1 for squamous cell bladder tumours). In a study
on schistosomiasis and the risk of bladder cancer in Egypt, Poggensee and Feldmeier (2001)
assessed the interaction of history of urinary schistosomiasis with smoking. The interaction was
significant (P<0.01), with an odds ratio of 15.8(95% cl: 5.1-48.4), and odds ratios for
schistosomiasis only and forever smoking only were 11.8(95%cl: 2.8-50.1) and 13.8(95% cl:
4.7-40.1), respectively.
19
1.2.8 Cancer of the female genital tract
Other than urinary bladder cancer, cervical cancer and other malignancies of the female genitalia
have been the most frequently reported cancers in association with Schistosoma haematobium
infection, usually in the form of case reports (International Agency for Research on Cancer,
1994). Recently, a number of additional cases of female genital malignancy in association with
evidence of Schistosoma haematobium infection have been published (North et al., 2003). Two
cross-sectional, one case-control and one pooled re-analysis studies have been published on the
association between Schistosoma haematobium and cervical cancer (Wright et al., 1982;
Moubayed et al., 1994; Parkin et al., 1994; Riffenburg et al., 1997). Parkin et al. (1994)
consulted the same cancer registry from Zimbabwe as previously described for bladder cancer
(Vizcaino et al., 1994). Riffenburg et al. (1997) pooled the data from the two earlier published
studies. None of these studies showed a positive association between the risk for cervical cancer
and infection with Schistosoma haematobium. The Working Group noted that possible
confounding by age, smoking or human Papilloma virus (HPV) was not considered in any of the
studies.
1.2.9 Effects of Schistosoma haematobium infection on detoxifying enzymes
Schistosoma haematobium infection has been found to markedly decrease the activity of the
carcinogen-metabolizing enzymes GST and NDMA-N-demethylase in human bladder cancer
tissue (Sheweita et al., 2004). The Working Group noted that this may change the capacity of the
bladder to detoxify many endogenous compounds, and may potentiate the effects of bladder
carcinogens such as N-nitrosamines.
20
1.2.10 Symptoms of urinary schistosomiasis
The initial symptoms are the intense irritation and skin rash, also called “swimmer’s itch” at the
site of cercaria penetration (Ugbomoiko et al., 2010). Other symptoms in the early stages of
infection include cough, headache, loss of appetite, various rashes and pains, and difficulty in
breathing followed by the initial irritation (Vennervald and Dunne, 2004). In heavy infection, the
urine appears reddish and the condition is termed gross, visible or macro-haematuria (WHO,
2004). However, in a long standing and light infection, the haemoglobin components in the
urine may not be visible to the naked eye and it is termed micro haematuria (Musa et al., 2010).
This can only be detected in the urine by the use of chemical reagent strip or under the
microscope. This haematuria present in urine is a confirmatory symptom resulting from the
puncture of blood vessels by the eggs in the urinary bladder (Ivoke et al., 2014). In endemic
areas, Mott et al. (1985) observed that 80% of infected children experience haematuria (blood in
urine), dysuria (painful urination) and proteinuria. Haematuria and proteinuria among infected
children is related to the intensity of Schistosoma haematobium infection (Mott et al., 1985).
In some cases, there are renal obstruction with kidney damage and squamous cell bladder cancer
(Poggensee and Feldmeier, 2001). Eggs lodged in the walls of the bladder and surrounding
tissues form granuloma; some eggs die and become calcified, producing what is known as
“sandy patches in the bladder (Awogun, 1990). Anaemia is a common feature in urinary
schistosomiasis, especially in people with low dietary iron intake (Okanla et al., 2003). The
rhythm of Schistosoma haematobium eggs secretion peaks in the late morning and early
afternoon. It has been recorded by many researchers that physical exercise and fluid intake
before micturation could increase egg output significantly (Oniya and Odaibo, 2006).
21
However, Cheesbrough (1989) reported that neither exercising before passing urine or collecting
terminal urine, increase the number of eggs present in the specimen. Once female fluke begins
oviposition, eggs can be found by either filtration or sedimentation method with the aid of
microscope (Ekwunife, 2003). 10ml urine egg count is the indices for estimating the intensity of
infection. Likewise egg burden in tissue and the number of worm pair are good measure of
intensity. Study has shown that males have a higher egg output than females (Lengeler et al.,
2002).
1.2.11 Diagnosis
The use of self-reported schistosomiasis or self-reported blood in urine should be continually
supported as a simple, cheap and cost effective tool for identifying people at risk of
schistosomiasis. WHO (1995) reported that rapid assessment techniques have been widely
accepted and recommended for control programme intervention. Proper diagnosis is a control
measure used for detecting both urinary and intestinal schistosomiasis.
Although all the techniques available at present are characterised with diagnostic imperfection,
they play a very vital role in decision on individual and community treatment, evaluation of
chemotherapy and control measure (Nmorsi et al., 2005). Due to cumbersomeness of the use of
microscopy technique in field diagnosis of schistosomiasis, Mott et al. (1985) has developed a
simplified and indirect approach to the diagnosis of urinary schistosomiasis. This involves the
use of reagent strip for detection of haematuria and proteinuria in infected individuals. The
presence of reagent strip-detected haematuria and proteinuria has been reported to have high
specificity and sensitivity for the detection of a Schistosoma haematobium when used to screen
populations in endemic areas (Fildmeier and Poggensee, 1994). Emejulu et al. (1992) also stated
that present history of haematuria and microhaematuria detected by reagent strip has the
22
strongest association with Schistosoma haematobium infection followed by leucocyturia and
dysuria.
In cases of light chronic infection, eggs are usually difficult to detect hence the use of serological
and immunological diagnostic ways (Neafie and Matty, 1993). Nwosu et al. (2005) compared the
sensitivity of various serological methods for diagnosing recent Schistosoma infections and
found out that the Enzyme-Linked Immunosorbent Assay (ELISA) were the most sensitive
techniques for detecting antibodies in Schistosoma mansoni, and infected patients who were not
passing eggs. ELISA can give valuable information on both individual diagnosis and therapeutic
drug monitoring, as well as in epidemiological studies and disease control programmes. Emejulu
et al. (1992) also recorded that overall prevalence of Schistosoma haematobium based on the
detection of eggs in urine was 18.1% while the prevalence of antibodies to Schistosoma
haematobium specific microsomal antigen was 57.6% as detected by enzyme linked immuno
transfer blot (ELITB). Other serological tests in use include indirect haemagglutination tests, gel
precipitation technique, latex agglutination and circumovarial precipitation test.
Eosinophiluriasis has been evaluated as diagnostic parameter in schistosomiasis. Colley and
Addis (1998) have indicated that an 80% sensitivity, 86% specificity and 82% predictive value
of eosinophilia as diagnostic index to Schistosoma haematobium. These rates according to them
were significantly higher than those of proteinuria and leucocyturia taken in combination or
singly. Nanvya et al. (2011) have also assessed the efficacy of eosinophiliatonic protein in
Schistosoma haematobium morbidity.
Usefulness of ultrasound in morbidity study has been evaluated. Rudge et al. (2008) have
evaluated the usefulness of ultrasound in morbidity study in Poyang lake region. They were able
to record schistosome infection rate of 22.9% with prevalence of abnormal ultrasound findings in
23
the liver and the spleen. However, ultrasound diagnostic techniques are costly and time
consuming. In order to reduce the cost and time, new approach to diagnosis is established and is
based on the use of rapid assessment technique (Bruce, 1990). The approach uses simple
questionnaires to find out how prevalent the disease is among the people by the literate ones
(Chidozie and Danijan, 2008). This is followed by the detection of haematuria and proteinuria
using reagent strips in urine by the literate ones previously educated on the use of strips. Lastly,
the effort of the literate ones may be validated by biomedical scientists with reagent strips and or
counting of ova (Bassey and Umar, 2014). It has been experimented in Tanzania and 7 other
African countries by the Red urine study group (Kapito-Tempo et al., 2009).
Although the cost of diagnosis is reduced 8 times compared to conventional procedures, true
prevalence may be under estimated. This is because the method relies on recall. Ansell et al.
(2002) in their study have reported that ultrasound diagnostic technique was shown to be 3 times
more cost effective than urine filtration method in identifying infected individuals. It would have
resulted in a 1/3 (one third) of the infected people being missed. They also reported use of selfreported
approach for schistosomiasis firstly to identify high risk schools (for individual
treatment) which also appeared more cost effective than urine filtration and would have resulted
in only 8% of the infected people not being treated. Definitive diagnosis of schistosomiasis is
generally made by detecting eggs in stool or in urine samples of the patients. Kato smear
techniques and formal ether concentration techniques are the standard methods for intestinal
schistosomiasis diagnosis (Gordon and Stapleton, 2005). For urinary schistosomiasis,
centrifugation and filtration methods are the best for detecting the eggs in urine. Centrifugation
may be adapted for routine diagnostic test, whereas a filtration technique which gives excellent
quantitative result is for field studies (Bethony et al., 2004).
24
1.2.12 Pathological effects of urinary schistosomiasis
Humans experience a lot of problems when infected with cercaria of the flukes. Ugbomoiko et
al. (2010) reported earliest sign of infection as intense irritation and skin rash known as
swimmer’s itch, after swimming in infected water. Early signs of morbidity to Schistosoma
haematobium and Schistosoma mansoni which manifest in school age children are anaemia,
impaired growth and development, poor cognition and sub-standard school performance (WHO,
2007). The ultimate pathological result of infection depends on the species of the invading
schistosome and on the host response to the juvenile and adult worms and to the eggs (Nmorsi et
al., 2007).
The major pathological agent is the egg containing the living miracidia. Pathology then results
from the delayed hypersensitivity reaction to schistosome eggs in various tissues (Doehring et
al., 1985). The severity is mostly related to the intensity of infection, although other factors are
involved. It has been estimated that the geometric mean egg output was 6,000,000 eggs per
Schistosoma haematobium worm pair (Doehring et al., 1985). This is about 20 times than that of
Schistosoma mansoni (Farid et al., 1968). Egg which pass through the tissues and discharged to
the surface cause little damage. Only about half of the eggs produced by the female schistosome
leave the body in the form of faeces and urine, the rest remain embedded in the body where they
cause damage to organs (Anosike et al., 1992). The first clinical signs are due to response of the
immune system to the eggs lodged in body tissue from which most of the subsequent pathologic
effects emanate (Nmorsi et al., 2007).
These clinical signs are produced either by the eggs, cercariae or schistosomules but the eggs are
the major cause of pathology. Man therefore suffers according to the number of cercaria which
can successfully penetrate his unbroken skin and survive to maturity (Butterworth, 1998).
25
Generally, human schistosomiasis passes through four recognisable stages which according to
Rudge et al. (2008) can be considered separately as;
Ø This stage involves the invasion of the host by cercaria through the development and
migration of schistosomulum to the eggs producing adult. Cercariae dermatitis caused by
invading non-human schistosome cercaria can be induced at this point.
Ø This is the deposition of eggs in the various organs and their passage in the excreta. This
stage may be associated with acute, sub-acute inflammatory hypertrophic, toxic or
allergic reaction to the host.
Ø This stage involves tissues reactions, such as fibrosis. Repairs can be affected at this
stage. Anatomical complication may commence and the passage of eggs is maximal.
Ø Here, there are possible irreversible anatomical changes. Eggs may no longer be passed
during this stage.
1.2.13 Prevention/Control
Control measures are very necessary to reduce, if not eradicate this life threatening disease. In
planning for adequate preventive and control measures against schistosomiasis, Nnoruka (2000)
emphasized on the following areas:
Ø Health education.
Ø The supply of adequate drinking water and the planning of adequate health care facilities.
Ø Diagnosis and treatment.
Ø Management of the environment.
Ø Control of the fresh water snail intermediate host.
Ø Building foot bridges across infected rivers.
26
Control approaches for each of the schistosomiasis vary and should depend on epidemiological
situations, available financial resources and particular local culture (Nnoruka, 2000). This
strategy has produced excellent result; in some regions it has met the planned objectives within
20 years. It is nevertheless essential to plan surveillance and maintenance over period of 10 to 20
years. Health education on schistosomiasis has greater importance than ever before. The
introduction into schools of the diagnosis and treatment has made children and parents much
more aware of the problems connected with the disease (Useh and Ejezie, 1996). Campaigns in
the Egyptian mass media have proved particularly successful in increasing awareness of the need
for diagnosis and treatment. The supply of safe drinking water is fundamental to schistosomiasis
control. The high prevalence of schistosomiasis is clearly a reliable criteria to select communities
for installing a clean water supply (North et al., 2003). Prevention and control of schistosomiasis
has its ultimate aim, the interruption of the life cycle of the parasites thus bringing about a break
in transmission. This depends largely on the understanding of the biology, ecology and
distribution of the parasites, the intermediate snail host(s) and mammalian reservoir of infection
(Ivoke et al., 2014).
Although this disease remains a major public health concern in many parts of the world
particularly in the poorest developing countries, cost effective solutions are both available and
desirable (Chitsulo et al., 2000). Approaches have been developed for the control of
schistosomisasis; they include aggressive chemotherapeutic and defensive approaches. One of
the approaches which hold out the greatest promise in the control of schistosomiasis is
aggressive snail control (Pearce, 2003). The snail as the intermediate host is considered the
greatest link in the disease cycle. Different methods of snails control have been tried with
varying degree of success. Of these, the greatest success has been achieved with chemical control
27
using molluscide (Ukoli, 1990). The molluscicide in use include Sodium Pentachlorophenate,
Copper Sulphate Aqualin, (Acrotein), Niclosamide (Bayliscide), Nitritymorpholine. However,
Niclosamide is the molluscicide of choice. In addition, there are many compounds like the
organition and organo-lead components which are effective snail killers and may prove useful
(Ukoli, 1990). Several attempts have been made to develop natural products with strong
mollusicdal properties and causing less harm to the environment from plants. The most
significant contribution in this direction has been made by Lengeler et al. (2002) in Ethiopia
where he produced the compound Endod from the fruits of the plant Phytolaca dodecandra which
is an effective molluscicide. Neafie and Matty (1993) in Ibadan recorded that extracts from a
sub-aquatic macrophyte, Alternautera sessile has a mollusicidal, ovacidal and cercariacidal
properties. Useh and Ejezie (1996) noted that the highly potent sapanius as a group of glycosides
in the berries of Phytolaca dodecandra appear to be the most promising chemical of plant origin
for snail control.
In addition to chemical control, other methods are also employed. These include the reduction of
the carrying capacity of the habitat either by habitat alteration or by the introduction of
competitors such as that the habitat is only able to support a small population of the target
species, reduction of snail rate of natural increase through the influence of predators and
parasites, and genetic manipulation mainly by developing non-susceptible strains of the snail and
introducing them into the environment (Ukoli, 1990). Schistosomiasis control has been shifting
from the snail host towards a direct attack on the parasite, through the large scale application of
chemotherapy. It is an effective form of control that reduces both the number of eggs in the urine
and in the body (Ivoke et al., 2014). Generally, the control of schistosomiasis requires an
integrated practice which includes the analysis of the macro-determinant factors such as basic
28
sanitation, habitation, education and health care (Gryseels et al., 2006). Individual protection
from infection as in the case of travellers can be achieved by avoiding contact with unsafe water
(Anosike, 1992). However, this requires an understanding of the risk of contact with water as
knowledge of the site where infected snails are likely to occur for people living in areas of
endemicity, contact is often unavoidable or difficult to prevent (WHO, 1995).
No vaccine is available, nor is any drug recommended as chemoprophylactic agents. Because
there is no practical way for the traveller to distinguish infested from non-infested water,
travellers should be advised to avoid swimming or other contact with fresh water in disease
endemic countries (Chitsulo et al., 2000). Untreated pipe borne water coming directly from
canals, lakes, rivers, streams or springs may contain cercaria but heating bathing water to 5oC for
5 minutes or filtering water with fine mesh filters can eliminate the risk of infection. If such
measures are not feasible, travellers should be advised to allow bathing water to stand for 2 days
because cercaria rarely remains effective longer than 48 hours (Chitsulo et al., 2000). Swimming
in adequately chlorinated swimming pools is virtually always safe, even in disease endemic
countries (Okafor, 1990b). Vigorous towel drying after accidental exposure to water has been
suggested as a way to remove cercaria before they can penetrate the skin. However, this may
prevent only some infections and should not be recommended to travellers as a preventive
measure. Although typical application of the insect repellent can block penetrating cercaria, this
effect is short lived and cannot reliably prevent infection (Ugbomoiko et al., 2010).
1.2.14 Treatment of urinary schistosomiasis
Latif (2004) recommended praziquentel as the effective drug of choice for treating Schistosoma
infections. According to WHO (1995), the most feasible approach to the control of
Schistosomiasis is chemotherapy. Surgical method could also be used depending on the degree
29
of infection (Bassey and Umar, 2004). Chemotherapeutic agents such as antimony compounds
were the earliest antischistosomidal agents for the treatment of schistosomisasis reported, but
they are toxic and have been superseded by Niridazole (Amilharz).
Currently, three safe and effective drugs are now available for the treatment of schistosomisasis
and they are now included in the WHO model list of essential drugs. They are Praziquentel,
Oximiquine and Metriphonate (WHO, 1999). Comparison of different chemotherapy strategies
against schistosomiasis has been demonstrated. Accordingly, Praziquantel (Bitricide) is highly
effective against Schistosoma haematobium than the other species (Latif, 2004). The normal dose
is 25mg per kg per day orally in three divided doses for 5 days. Metriphonate (Bilacil) is only
effective against Schistosoma haematobium (WHO, 1999). The recommended dose is 7.5 to
10mg per kg orally taken three times at two weeks intervals.
Pugh et al. (1980) in Malumfashi endemic disease research project (V) reported that concurrent
single dose of Metriphonate, oximiquine and Niridazole is very effective in the treatment of
urinary schistosomiasis. These three drugs are contra-indicated if there is any previous history of
psychiatric illness, renal failure or any intercurrent infections. Surgical measure could be applied
usually in the treatment of the bladder in later stages of urinary schistosomiasis especially if its
capacity is severely restricted or if patients suffer pain and fatigue. It is the method of choice if a
carcinoma is found in its early stage (Poggensee and Feldmeier, 2001).
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