Epidemiology and Transmission Patterns of Schistosoma haematobium Infections in Central Ebonyi State, Nigeria
Chapter One
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:
- Determine the prevalence and intensity of Schistosoma haematobium infection among inhabitants of Ebonyi Central senatorial
- Determine types of water-contact activities in the study communities in relation to Schistosoma haematobium transmission.
- Identify the intermediate hosts of Schistosoma haematobium at the water-contact sites
CHAPTER TWO
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, 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.
Life cycle of Schistosomahaematobium
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 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).
CHAPTER THREE
MATERIALS AND METHODS
Study Area
The study area (Ebonyi Central, Ebonyi State; see figure 2) consists of four Local Government Areas (Ishielu, Ezza South, Ezza North and Ikwo Local Government Areas). According to Nigeria Population Commission (NPC, 2006), Ebonyi Central Senatorial Zone covers a total land area of 3,364km2 (Uneke, 2011) with a population of 578,604 people. The population live in scattered village settlements that are entirely rural. The study area lies between latitudes 6000”N and longitude 7040”E. The climate of the area is tropical and the vegetation characteristics is predominantly the Guinea savannah with an average annual rainfall of about 1,300mm and average atmospheric temperature of 300C between June and December but rises from 31 – 350C between January and April (Uneke, 2011) . There are two distinct seasons in the area, the wet and dry seasons. The former takes place between April and October, while the later occurs from November to March. Most of the communities in the area lie below 300 metres above sea level on the plain of Ebonyi River. The inhabitants of the study area are predominantly farmers. The major farm produce include yam, cassava and rice which is grown in the swamp fields. Some inhabitants of the study area also engage in lead excavation, dredging of sand from Ebonyi river and quarry activities. The fresh water hydrology of the study area is dominated by the Akpara stream which bisects the area and flows in a north-south direction into the bigger Ebonyi river that demarcates the southern periphery of Ebonyi central senatorial zone
Selection of communities
Sixteen communities (See figure 3) out of fourty seven communities that make up the four Local Government Areas of Central Ebonyi State were randomly selected for this study due to reported cases of schistosomiasis in the area, that is, four communities from each of the four Local Government Areas. The sixteen communities are Agba, Amuzu, Echara, Enyibichiri, Igweledeoha, Nchionu, Amagu, Alike-Ikwo, Ntezi, Ogboji, Ohaigbo, Ohoffia, Umuoghara, Okpoto, Oshugbu and Umuome. In Ikwo Local Government Area with a population of 165,302 people (NPC, 2006), the four communities studied include Alike-Ikwo, Enyibichiri, Nchionu and Echara. In Ezza South Local Government Area with a population of 124,000 people (NPC, 2006), the four communities studied are Amagu, Amuzu, Ohaigbo, and Oshugbu. In Ezza North Local Government Area with a population of 143,631 people (NPC, 2006), the four communities studied include Igweledeoha, Ogboji, Umuoghara and Umuome while in Ishielu Local Government Area with a population of 145,671 people (NPC, 2006), the four communities studied are Agba, Ntezi, Ohoffia and Okpoto.
CHAPTER FOUR
RESULTS
Prevalence of Schistosoma haematobium Infection
The overall prevalence of Schistosoma haematobium infection in Central Ebonyi senatorial zone was 19.0% (n=342) which falls within WHO classification of endemicity, with the prevalence in different communities within the zone ranging from 6.6% to 32.2% (See table 1).
Prevalence of infection in the Study communities
Table 1 shows the summary of the study conducted in sixteen communities in the four Local Government Areas that make up the Central Ebonyi State for Schistosoma haematobium infection. A total of 1800 persons were examined using reagent strips between July, 2013–April, 2014. The infection was recorded in all the communities in the study area with Enyibichiri (32.2%, n=39) having the highest prevalence followed by Umuoghara (25.5%; n=26) while Oshugbu (6.6%; n=5) had the least prevalence. Across communities, the prevalence of the infection differed significantly (X2=71.049; P<0.0001).
CHAPTER FIVE
DISCUSSION
The overall prevalence of Schistosoma haematobium infection recorded in Cental Ebonyi State was 19.0% which falls within the WHO classification of endemicity (WHO, 2002). The present study supports a number of previous reports in this geographical region which have consistently shown that Schistosoma haematobium infection endemicity in Nigeria is on the increase particularly in the rural areas, with school aged children at the greatest risk (Korve, 2002; Okoli and Odaibo, 1999). Poverty, ignorance, inadequate sanitation and water supplies as well as deplorable personal and environmental hygiene characteristics of many rural communities in Nigeria as in other developing tropical countries are identified as important factors contributing to increase in transmission of schistosomiasis (WHO, 1999).
The high prevalence rate of urinary schistosomiasis in Central Ebonyi state may be attributable to low literacy level, lack of basic amenities, proximity of infested water bodies like streams, quarry pits, ponds and the biggest river (Ebonyi river) where daily chores activities like washing, fetching of water domestic uses, fishing, irrigation, swimming and bathing take place, as well as inadequate and indiscriminate disposal of human sewage. This is similar to observations made by Ivoke et al. (2014) who recorded a prevalence rate of 15.3% at Okposi in Ebonyi state and Uneke et al. (2007) who recorded a prevalence rate of 11.0% at Onicha in Ebonyi state while Anosike et al. (2001) recorded a prevalence rate of 21.5% at Ikwo in Ebonyi State. Anosike et al. (2006) also obtained a prevalence rate of 22.1% at Ezza in Ebonyi state but Ezeagwuna (2010) recorded a prevalence rate of 15.3% at Umuikwu-Anam settlement in Anambra state. Egwunyenga et al. (1994) recorded a prevalence rate of 21.2% in Bauchi state while Chidozie and Danijan (2008) recorded prevalence rate of 12.9% in Minna. Ugbomoiko (2000) also recorded a prevalence of 22.9% in three geographical zones in Edo state. In contrast, the result obtained in this study is lower than the high prevalence rates of 25.7%, 30.6%, 40.7%, 43.8%, and 47.9% reported by Ekwunife et al. (2008) at Ndokwa East, Delta state; Abolarinwa (1999) at Esie community of Kwara state; Ameh (2008) at Ginga village in Kebbi state; Oniya and Olofintoye (2008) in Ondo state and Uneke et al. (2007) at Ohaukwu Local Government Area in Ebonyi state respectively, all in Nigeria. Similar studies in other sub-Saharan areas of Africa have been reported. These include a prevalence of 47.6% in Dar-es-salam Tanzania, reported by Ndyomugyenyi and Minjas (2001) while 50.8% was recorded in South-West Cameroon by Nkengazong et al. (2009). Sama et al. (2007) obtained a prevalence rate of 32.1% in Kumba, Cameroon but Brouwer et al. (2004) recorded a prevalence rate of 60.0% among school children in Zimbabwe while Kapito-Tempo et al. (2009) reported a prevalence of 10.4% among school children in Blantyre district, Malawi. This variation as reported by earlier researchers may be attributable to the variation in the degree of exposure to infection as well as the variation in the ecological conditions necessary for the breathing of the snail intermediate hosts of the disease.
A close look at the prevalence of infection for the communities studied, showed variations which can be interpreted to mean that transmission was higher in Enyibichiri (32.2%) followed by Umuoghara (25.5%) while at Alike-Ikwo it was (23.5%). This is similar to observation made by Ekejindu et al. (2002) who reported a prevalence rate of 25.5% in the farm settlement of Ezi- Anam, Okoli and Iwuala (2004) in selected foci in Imo state (25.1%), and Anosike et al. (2003) in Ebonyi- Benue river valley (24.2), South Eastern Nigeria. The least prevalence rate was recorded in Oshugbu (6.6%) which could be due to availability of bore-hole which supplies them with safe water for their domestic uses, thereby reducing their contact with infested ponds, thus reducing the infection. This shows the important role safe water supply plays in the control of urinary schistosomiasis as reported by Udonsi (1990), Okoli et al. (2006), WHO (2007) and Uneke et al. (2007). In this study, the prevalence rate of infection was observed to be higher in males (20.3%) than females (16.9%) (P<0.05), similar to the work of Ivoke et al. (2014) where males had a significantly higher prevalence rate of 20.7% than the females (7.6%) and Ekejindu et al. (2002) with males (29.3%) recording higher infection than the females (16.3%). Mba and Useh (2008) also reported a significant higher rate in males (23.5%) than females (15.7) in a rural community in Cameroon. Ameh (2008) recorded a higher rate among the males than females (43.1% against 37.6%). They reported that sex is not significant in the distribution of infection but could be due to socio-cultural and religious factors that expose males to activities at the infested ponds, such as fishing, swimming and bathing thereby increasing their rate of exposure to infection. Among the muslims, the females are restricted from swimming and bathing in water bodies due to religions and socio-cultural practices and therefore this reduce their chances of being highly infected when compared with their male counterparts (Ogbe, 1995).
In contrast, Ekwunife et al. (2008) observed that sex played no significant role in Schistosoma haematobium distribution among sexes because of equal water contact activities by both sexes. Therefore, persons who have greater contact with the breading foci have higher prevalence of the disease, irrespective of the sex of the individual (Ivoke et al., 2014; Uneke et al., 2007; Ndyomugyenyi et al., 2001). In this study, the highest prevalence of infection among various age groups was recorded among the age group 11 – 20 years (27.3%) which is similar to a report by Ekejindu et al. (2002) who recorded a high prevalence rate among the age group 10 – 14 years. Okon et al. (2007) also recorded highest prevalence rate among 12 – 18 years while Bello et al. (2003) observed highest prevalence in 10 – 19 years age group. In contrast to the above observations, Ekwunife et al. (2008) and Mba and Useh (2008) recorded a higher rate among the age groups 5 – 9 years with a rate of 45.9% and 45.7% respectively, while Ameh (2008) recorded a higher prevalent rate (47.8%) among the age group 21 – 30 years. This could be attributed to the fact that young people are more engaged in unrestrained water contact activities such as swimming and bathing, therefore they are more likely to contact cercaria and acquire infection. The least prevalence was observed among age group 31–40 years which may be attributed to the low human-water contact pattern as a result of maturity or awareness of the source of infection. Immunity can as well play a role here as observed by Abebe et al. (2001). The onset of infection noticed in boys and girls in the age group 0–10 years could be because of early exposure to ponds as mothers in the studied communities usually go to the farms with their infants and bath their children in infested ponds or streams after the daily farm work. The decrease in prevalence rate with increase in age could also be due to reduced water contact and increased immunity with increase in age as reported by Okoli et al. (2006) and Uneke et al. (2007). In this study, it was observed that the transmission of urinary schistosomiasis is higher in the dry season than in the rainy. This may be attributed to the fact that the vulnerable school age children are not allowed to visit water bodies during rainy season for fear of being drowned because of high water level at this period. Harvested rain water also solve our immediate water need rather than going to the stream. But in dry season, one is left with no option than to go to the nearby water bodies for your contact activities. The results of human water contact activities in the study area shows a marked seasonal variation in both the frequency and duration of water contacts. A similar trend was reported by Ugbomoiko (1998) who observed peak water activity during the dry season and least in the periods coinciding with heavy rainfall in Ikpeshi, Edo State Nigeria.
In any intervention programme, therefore, focal attention should be on the most heavily infected, which in this study is the 11–20 years age group. Considering the egg count load of the infection, intensity studies showed that majority of people examined in this study have light to moderate infection. Of the 342 infected persons in the studied communities, 60.5% were excreting below 50eggs/10ml urine, 32.5% were excreting between 50–100eggs/10ml urine while only 7.0% were excreting above 100eggs/10ml urine. Consistent high intensities were recorded for age groups of 1–30 years but peak intensity was observed within 11 – 20 age groups. About 10.2% of the 138 infected candidates in 11–20 years category were also excreting over 100eggs/10ml urine. There was a decrease in heavy intensity from 0–10 years. From 31 years upwards, no candidate was observed excreting more than 100eggs/10ml urine.
The World Health Organisation (WHO, 1985) set a threshold egg intensity of >50eggs/10ml urine to indicate the risk of Schistosoma haematobium morbidity at the level of the individual. Haematuria was the predominant presenting symptom observed among the infected persons. Haematuria as observed herein showed that 188 (55.0%) of the 342 infected individuals had visible haematuria. This finding is in line with the report of Emejulu (1994) and Anosike et al. (2003) who reported a significant relationship between haematuria and the presence of Schistosoma haematobium ova. Haematuria in urinary schistosomiasis in this study showed similar age prevalence pattern as a greater number of individuals within the 11 – 20 years category (62.3%) had haematuria, which then decreased with increase in age, a phenomenon attributed to the waning of egg hypersensitivity with age (Nduka et al., 1995).
Considering the occupation related prevalence, farmers had the highest infection rates of 35.4% compared with other occupational groups. This could be attributed to their frequent contact with water bodies as they perform water-related activities such as rice farming and bathing. Majority wash their bodies after a hard day’s work in a nearby water body, exposing themselves to cercaria. The students/pupils had the second highest infection rate due to their swimming habits which may be during or after school. They are followed by civil servants while artisans had the least infection prevalence due to the nature of their work which guarantees reduced contact with water bodies.
This study has revealed that persons between the age group of 0–20 years are important in the spread of this disease, since the first two decades of life is the age of active life, hence increased human activity increase the predisposition of people in this age group to infection especially through increased water contact (Ivoke et al., 2014; Uwaezuoke et al., 2006). Personal and economic activities were found to be the principal activities of both males and females and are therefore considered as risky contacts. It was also observed that the recreational contacts were mostly recorded during the dry season when water level is low. This is attributed to the high rise of water level during the rainy season which scares people from going to water sites for their water related activities for the fear of being drowned. Also, people can still perform their major water related activities at home during the rainy season with harvested rain water leaving them with little or no reason of going to the stream.
The report from this study is an indication that the school children, teenagers and young adults are the population at risk of schistosomiasis infection in the study area. The pattern of seasonal variation observed in this study suggests that transmission occurs in dry season. The highest frequency of contact recorded among school age children and teenagers of age groups 10 – 20 years and young adults 20 – 30 years conforms to the reports of several workers in tropical Africa (Dalton and Pole, 1978; Tayo et al., 1980; Kloose et al., 1983; Chandiwana et al., 1987; Ugbomoiko, 2004; Owojori et al., 2006). Bulinus globosus has been incriminated as a vector of
Schistosoma haematobium (Ejezie et al., 1989; Arene et al., 1989). While snail population increased with the volume of rainfall, snail infection was higher in the drier months. Identification of the snails collected from various fresh water bodies showed five snail species. They include Bulinus globosus, Bulinus truncates, Bulinus forskali, Bulinus senegalensis and Lymnaea natalensis. The relative abundance of Bulinus globosus and its high infection revealed that this snail species is responsible for the transmission of urinary schistosomiasis in Central Ebonyi State, Nigeria.
Conclusion/Recommendation
Based on the findings of this study, which showed that the prevalence of the Schistosoma haematobium infection in the Central Ebonyi State falls within WHO classification of endemicity of schistosomiasis. This shows that urinary schistosomiasis is still on a high trend in the area. Thus, suggesting that there might be more foci of endemic urinary schistosomiasis in the South Eastern Nigeria than previously reported. Urinary schistosomiasis contributes to malnutrition among residents of rural agricultural community in developing countries where poverty, ignorance, ecological conditions and lack of government commitment among other factors constitute serious threat to public health. This disease is thus highly prevalent in most settlements in Nigeria and would be a threat to important socio-economic development in all the infected areas.
Notwithstanding the efforts made to control schistosomiasis in endemic areas, global incidence of the disease is still increasing. To disrupt transmission more effectively and achieve prolonged disease control, it is hereby recommended that there is need for schistosomiasis control program in the state. This is to educate the populace on risk factors that predispose them to urinary schistosomiasis such as good personal hygiene, supply of safe drinking water, diagnosis, treatment, management of the environment and control of the intermediate host. Since personal and economic contacts were considered as the principal contacts in the water body, people making such contacts should be educated on the implication of their involvement with the water. Also, the report from this study is an indication that the school age children, teenagers and young adults are the population at risk of schistosomiasis infection and it will provide a guide for the treatment of people and help in eradicating schistosomiasis infection in the study area. Health education of the community members, including school children should be continuously embarked upon. This would not only serve as a reminder to those that are already aware of the disease but also as a source of information to the migrants in Central Ebonyi State. Teachers and church leaders are essential tools in this regard and should be encouraged and equipped with necessary information on the risk of water contact activities. Government should provide enough bore-holes across the communities to minimize the use of unsafe drinking water. This is to discourage children from having little or no reason to visit the streams until the vector and intermediate host are eliminated. The state government should provide toilet facilities in schools and markets within the study area. Treatment of urinary schistosomiasis is by mass chemotherapy and focal application of molluscicides in the community ponds during the dry season. Praziquantel should continue to be the drug of choice for the treatment of schistosomiasis due to its high rate of compliance with the recommended dose, however criteria of cure should be taken into consideration, to avoid the attribution of unequivocal efficacy of this drug especially in chronic cases.
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