Prevalence and factors associated with urogenital schistosomiasis among primary school children in barrage, Magba sub-division of Cameroon

Schistosomiasis or bilharzia is a parasitic disease caused by blood-dwelling flukes of the genius Schistosoma. Schistosomiasis affects 240 million people worldwide [1]. Every year, an estimated 200,000 people die from the disease [2, 3]. The infection is more prevalent in poor communities without portable water and adequate sanitation, characteristic of most developing countries in Africa, Asia and South America. A great majority (85%) of cases occur in Africa [4]. An estimated 700 million people, in more than 70 tropical and sub-tropical countries, live in areas where the disease is common [2]. In tropical countries, schistosomiasis is second only to malaria as the most important parasitic disease with the greatest economic impact [5].

Schistosomiasis can be grouped into two categories based on the organ affected – urogenital schistosomiasis and intestinal schistosomiasis. Urogenital schistosomiasis is caused by Schistosoma haematobium and intestinal schistosomiasis by any of the following organisms namely; S. guineensis, S. intercalatum, S. mansoni, S. japonicum, and S. mekongi. Among the schistosomes, S. haematobium is the deadliest [6]. It infects over 112 million people annually in sub-Saharan Africa Alone [6].

Schistosomiasis is highly endemic in Cameroon but its distribution is uneven. Prevalence is higher in the northern regions. Unlike the northern regions where infection is widespread, transmission in the southern regions is focalized to areas where the snail intermediate host are found [7]. Prevalence of schistosomiasis in the country ranges from 1.7 to 55.5% [8‐12] and rural communities are the most affected. In the west region where this study was performed, the prevalence is estimated at 3.98% [10]. Species of schistosomes endemic in Cameroon include S. haematobium, S. mansoni and S. intercalatum [13, 14], with the former being the most prevalent. Schistosomiasis in Cameroon affects mainly school-aged children [15]. The development of dams for hydroelectric power, irrigation canals and lack of portable drinking water are some of the factors that have greatly contributed to the high prevalence of schistosomiasis in the country [16]. The variation in the distribution of schistosomiasis in Cameroon also extends to the snail intermediate host; Bulinus globusus and B. senegalensis are the most common hosts transmitting S. haematobium in the northern half of the country meanwhile B. truncatus is the principal host transmitting S. haematobium in the southern half [17].

Control of schistosomiasis in Cameroon is embedded in the National Control Program for NTDs and generally involves the distribution of several drugs to school-aged children including membendazole, albendazole, ivermectin and praziquantel, with the latter distributed only in high endemic areas of schistosomiasis [10, 18]. Despite considerable efforts to scale-up activities to encompass all the regions in country, coverage still remains poor in rural areas, partly as a result of the unavailability of documented transmission [18]. For example, in Barrage, a rural community in Magba subdivision in the West region of Cameroon, all the factors that favour transmission of schistosomiasis are present including the presence of a dam to generate electricity, irrigation scheme, absence of portable water and the snail intermediate host, but no documented transmission of schistosomiasis in the area exists. This study was aimed at determining the prevalence and intensity of urogenital schistosomiasis as well as determine the associated factors for infection in the study area, so as to generate baseline data that may raise awareness of the impending problem and also mobilize control efforts directed towards the study area.

Out of the 413 children approached, 382 provided urine sample and were included into the study. Those excluded did not differ from those included in the study in terms of their age (p = 0.285) or gender (p = 0.604). The sex ratio (M/F) of the participants was 1 with 191 males and 191 females. The ages of the participants ranged between 7 and 14 years (mean ± SD = 10.2 ± 1.9). The majority of the participants were recruited from EP Matta Barrage.

The most frequent clinical presentation observed in the children was passage of bloody urine or haematuria 125 (32.7%) (Table 1).

A majority (57.9%) of the participants admitted to be using water from the dam for bathing and other household chores (Table 1).

Among the 382 participants, 157 were shedding eggs of Schistosoma haematobium in their urine, giving an overall prevalence of 41.1% (95% CI: 36.1–46.2). The prevalence of urogenital schistosomiasis (US) was significantly higher in children below 10 years (p = 0.009), and in males (p = 0.029) (Table 2). The prevalence of US was highest in children recruited from EP Manbonko Bord. A significant association was observed between prevalence of US and the primary school attended (p < 0.001) (Table 2). The prevalence of US was highest in children whose parents’ main occupation was fishing and lowest in children whose parents were civil servants. A significant association was observed between prevalence of US and the occupation of the parents (p < 0.001). The prevalence of US was significantly higher in children who had frequent contact with water from the dam (p < 0.001). No significant association was observed between prevalence of US and knowledge on the disease (p = 0.755).

A significant association was observed between prevalence of US and pain on urination (p < 0.001), increased frequency of urination (0.010), and haematuria (p < 0.001) (Table 2).

Overall, the mean parasite load was 154.7 (±8.3) ova/10 ml of urine. The intensity of infection was higher in children below 10 years (p < 0.001), and in males (p = 0.001) (Table 3). Children attending EP Manbonko Bord had the highest parasite load compared to children from the other schools (p < 0.001). The intensity of infection was highest in children who presented with haematuria compared to the other clinical presentations (p < 0.001) (Table 3).

Multinomial logistic regression analysis revealed that use of water from the dam and having a parent whose occupation was fishing were the factors associated with Schistosoma haematobium infection (Table 4).

The prevalence of urogenital schistosomiasis (US) observed in this study was 41.1%. The prevalence observed was similar to that reported in other foci in the South West region: 40.27% in Munyenge [9] and 41.3% in Marumba [21]. The prevalence of US observed in this study was however higher compared to the overall prevalence of schistosomiasis reported in the West Region [10] and in other areas of Cameroon: 1.7% in Kékem [12], 32.1% in Kumba [22] and 22.9% in Maroua [15]. These areas have regularly been targeted for control of schistosomiasis and geohelminths which may have accounted to the lower prevalence of schistosomiasis reported. Another reason that might have accounted for the lower prevalence of schistosomiasis observed in these studies compared to the current study could be the differences in the geographical settings; these studies were performed in urban and semi-urban settings meanwhile the current study was performed in a rural setting. Higher prevalence of schistosomiasis in rural areas have also been reported in other parts of the country [9, 16, 23, 24]. As noted by Njiokou et al. [23], urbanization reduces transmission points and the creation of modern water points limits the frequency of human water contacts.

In this study, haematuria, increased frequency of urination and pain on urination were identified as the most common symptom of infection with Schistosoma haematobium which is not very different from the findings in the study performed by Saotoing et al. [15]. Compared to the other clinical presentations of US, children with haematuria had significantly higher parasite load (p < 0.001). This suggest that higher parasite load is needed to cause the damage that leads to extrusion of blood into the bladder as seen during urination.

In the current study, schistosomiasis was significantly more common in males. The higher prevalence in males could be attributed to the higher tendencies of water contact through swimming, playing, fishing and engagement in other activities like the making of burnt bricks along infested water bodies besides the primary domestic activities of washing and fetching water which exposes both sexes to infection. The finding of higher prevalence of schistosomiasis among males in this study is in line with other studies performed elsewhere [14, 25‐27]. These findings are however contradictory to the study by Ntonifor et al. [9] and Ndamukong et al. [24] in which infestation with schistosomes were more common in females. The difference could be attributed to the fact that boys compared to girls were the ones who frequently come into contact with infested water either through playing, bathing, or fishing in the current study.

Infection with S. haematobium was observed to be more common in children below 10 years of age compared to children aged 10 years and above. The finding of lower prevalence of schistosomiasis in older children could be attributed to the fact that as the children grow older, they become more aware and begin to follow the basic rules of hygiene limiting their contact with infested water bodies. The finding of higher prevalence in children below 10 years is contradictory to the study by Ntonifor et al., [9] in which infestation was more common in older children. The difference between their studies and ours could be attributed to the different behavioural pattern and cultural practices of the different populations. Fishing is one of the principle activity of the inhabitants of barrage, and younger children are frequently expose as they come in contact with infested water through fishing, meanwhile in the study of Ntonifor et al. [9], the principal activity of the inhabitants was farming which explains why older children were more infected.

Urogenital schistosomiasis was observed to be more common in EP Manbonko Bord (p < 0.001). The high prevalence of US in this school was probably due to its close proximity to the dam where the children frequently move to the dam within a few minutes. Moreover compared to the other schools, this school was poorly constructed without cemented floors which needed to be constantly watered to avoid dust, and the dam was the only source of water closest to the school. All these increases the exposure of the children to infection. Similar observations have been reported in studies performed elsewhere [9, 28]. The prevalence of schistosomiasis was lowest in EP Matta village. This low prevalence in this school is understandably so because Matta village is about 2 km away from the dam, and the inhabitants tend to use water from the stream present in the area. This finding affirms the fact that closeness of the school to the dam has a bearing on the prevalence of schistosomiasis. The few children infected with S. haematobium in this school were probably those who went for fishing at the dam. The finding of significant association between prevalence of schistosomiasis and the school attended is contrary to the study performed in Kékem [12] in which no significant association was observed. This difference could be attributed to the low prevalence of US in Kékem. This therefore shows how control programs could be beneficial provided coverage was extensive especially in rural areas.

The mean parasite load was 154.7ova/10 ml of urine. The intensity of infection was significantly higher in children below 10 years. The intensity of infection was significantly higher in males. This may be a reflection of the frequency of contact with infested water; as mentioned earlier, in this study, children below 10 years and males were the groups that frequently come into contact with infested water and therefore tend to be infected on multiple occasion. This hypothesis is supported by the observation that in this study, the intensity of infection was higher in children attending EP Manbonko Bord, which was the closest school to the dam. The finding of higher parasite load in males in this study is contrary to the study by Nkengazong et al. [21] in which no significant difference was observed in the intensity of infection between males and females. The difference between this study and ours could be attributed to differences in the exposure between the two populations; unlike in our study where males were more exposed than females through fishing activity, in the study by Nkengazong et al. [21], the rate of exposure was similar between males and females since they frequent the lake in the area equally to get water for their domestic use.

In this study, frequent contact with water from the dam and having parents whose occupation was fishing were identified as the associated factors for infection with Schistosoma haematobium. Many inhabitants in Cameroon especially in rural areas have limited access to portable water for domestic use leaving them with the option of using natural water bodies such as lakes, rivers, ponds and dams which may be infested with the parasite. As the dam in Barrage was the main source of water for fishing and domestic use, it is more likely that the children became infected as the come in contact with the infested water. The finding of higher rate of infections in children whose parents had fishing as their main occupation is further incriminating to the dam as the source of the infections. Development of irrigation schemes and other water bodies have also been incriminated in the increase of transmission of schistosomiasis in other areas in Cameroon [9, 16, 29].

In this study, children were recruited only from the three schools mentioned above. The findings are therefore not generalizable to preschool and school-aged children not attending these primary schools. This constitute a major limitation to this study. Studies designed to target children at the level of the communities will therefore be needed to provide a clearer picture of urogenital schistosomiasis in the study area. Furthermore, this study relied only on statistical methods to establish the factors associated with schistosomiasis in the study population, studies will therefore be needed to confirm that the dam is infested with snails which harbour the infective larvae of the parasite.

This study shows a high prevalence of 41.1% for urogenital schistosomiasis in the study area putting Barrage within the WHO [30] classification as endemic. Prevalence of urogenital schistosomiasis was observed to be higher in children below 10 years and in males. Furthermore prevalence was observed to be significantly higher in children attending EP Manbonko Bord which is very close to the dam and in children whose parents’ main occupation was fishing. The intensity of infection was significantly higher in children below 10 years, in males and in children attending EP Manbonko Bord. Frequent contact with water from the dam and having parents whose main occupation was fishing were all observed to be the independent predictors of infection with Schistosoma haematobium. To effectively control transmission of the disease in the area will entails limiting contact with water from the dam, eliminating the snail intermediate host, educating the population and mass drug administration of praziquantel to the entire population of Barrage.