Background

Schistosomiasis known as bilharziasis or snail fever is a parasitic disease that seriously affects internal organs with the popular symptom being blood in urine and/faeces and an enlarged liver. The disease mostly affects the health of school-age children (Adeyaba & Ojeaga, 2002). Urinary schistosomiasis is a parasitic infection causing serious inflammatory changes and continues to damage different organs of the body. The infection is acquired through contact with cercaria-polluted water during washing clothes and utensils, swimming, wading or bathing (Akinboye et al., 2011).

More than 66 million people throughout 54 countries in Africa are affected by S. haematobium infection (Badmos & Komolafe, 2007). In S. haematobium infection, the eggs are trapped in tissues and cause progressive damage to the bladder, ureters and kidney. There is dysuria (painful urination) and haematuria (blood in urine) (Bello, Jimoh, Shiitu, & Hudu, 2014). In a study conducted in Nigeria, 26% of more than 1000 cases of appendicitis were attributed to S. haematobium (Carter Center, 2015).

The disease can present as chronic, which is most common, or acute. Haematuria (blood in urine) and dysuria (painful urination) are the main early symptoms of the disease. For most people who are regularly exposed, the severity of disease depends upon the intensity of infection. Mostly individuals with few schistosome worms, and especially adults, remain asymptomatic, although about 80% of infected children show early symptoms and signs of disease (Mott, 1983; Olds, 2000). It was estimated that 70 million individuals out of 282 had experienced haematuria and 32 million had dysuria associated with S. haematobium infection. It was estimated that 18 million suffer bladder wall pathology and 10 million had hydronephrosis (Van der Werf et al., 2003).

Parasitological diagnosis of S. haematobium infection is readily undertaken by urine filtration. While urine is easily collected, due to the circadian pattern of egg excretion, specimens should ideally be collected between 10:00 am and 2:00 pm and preferably after physical exercise (World Health Organization, 2012). For S. haematobium infection, the presence of micro- or macrohaematuria has enabled the development and validation of a range of indirect diagnostic tests useful for epidemiological mapping of prevalence, such as the dipstick methods which detect micro- and macrohaematuria (Guyatt, Brooker, Lwambo, Siza, & Bundy, 1999).

In children, schistosomiasis can cause anaemia and physical weakness and consequently reduce their ability to learn, although these negative impacts can be reversed with appropriate treatment. Chronic schistosomiasis may result in death. In sub-Saharan Africa, more than 200,000 deaths per year are caused by the disease (WHO, 2012).

If freshwater contact is unavoidable, bathing water should be heated to 50 °C for 5 min or treated with iodine or chlorine as for the treatment of drinking water. Water can also be strained through paper filters, or allowed to stand for 2 to 3 days before use. High waterproof boots or hip waders are recommended if wading through streams or swamps. Vigorous towel drying, and rubbing alcohol on exposed skin immediately after contact with untreated water, may also help reduce cercarial penetration. Vegetables should be well cooked and salads avoided as these may have been washed in infected water, allowing cercariae to attach themselves to the leaves (Robson, 2013).

Minimizing morbidity can be effectively supported through parallel preventive measures, i.e. reducing the contamination of water with schistosome eggs and at the same time preventing exposure of humans to schistosome-infested water (World Health Organization, 2002). Unfortunately, health education, water supply and sanitation programmes have only a marginal impact on the youngsters playing in and around water bodies and on people, whose occupation involves water contact. Therefore, snail control is an important preventive measure in an integrated approach to control schistosomiasis transmission (Madsen & Christensen, 1992; Sturrock, 2001).

Urinary schistosomiasis poses a public health problem. Despite the intervention, the disease still persists. This study was carried out to determine the prevalence of urinary schistosomiasis among primary school pupils in Wamakko Local Government Sokoto State, Nigeria.

Materials and methods

Study area

The study was carried out in Wamakko Local Government Area of Sokoto State, Nigeria, which lies between latitude 12° N and 13° 58 N and longitude 04° 8′ E and 6° 54 E (Fig. 1). Wamakko was estimated to have an area of 697 km2 and a population of 209,204 (National Population Census, 2015). Wamakko Local Government Area was described by the presence of hills, sandy savannah, in addition to numerous rivers, streams and dams. The annual rainfall is about 50 mm with the highest peak in August. The predominant tribe in Wamakko is Hausa. The residents were mainly farmers and fishermen (Kabiru et al., 2013).

Fig. 1
figure 1

Map of Nigeria, Sokoto State, and Wamakko Local Government Area showing the four districts

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Study design

A cross-sectional study was carried out in which urine samples were collected from the pupils and examined to estimate the prevalence of urinary schistosomiasis among primary school pupils in Wamakko Local Government, Sokoto State, Nigeria.

Sample size determination

The sample size was estimated using the single proportion formula with a confidence interval of 95% and a precision of 5%. N = Z2 pq/d2, where N = sample size to be determined, Z = standard normal deviate at 95% confidence interval (= 1.96), P = proportion of the population estimated to have attributed from the previous study, and this was obtained from the study conducted in Wamakko local Government by Kabiru et al. (2013) where they recorded a prevalence of 38.3%.

Collection of urine samples and parasitological examination

Each pupil was given a 30-ml sterile wide mouth, screw-capped plastic container carrying their identification number and was instructed on how to collect the urine sample. A total of 400 urine samples were collected between 10:00 am and 14:00 pm. The samples were taken to parasitology Laboratory, Usmanu Danfodiyo University, Sokoto, and were analysed using standard filtration technique as described by Pugh (1978). Questionnaires were administered to the pupils to obtain information on the source of drinking water and water contact activity.

Data analysis

Data obtained were summarized into tables. Prevalence was calculated using the formula: No. of pupils infected/(No. of pupils examined) × 100. Chi-square (χ2) statistical analysis was used to determine the association of frequency of infection occurrence with schools, class, sex, age, the source of drinking water and water contact activity. p values less than 0.05 were considered significant. Data were analysed using Quantitative Parasitological (QP) Software version 3.0.

Results

Schistosoma haematobium infection was recorded among primary school pupils in Wamakko Local Government, Sokoto State. Out of the 400 samples examined for urinary schistosomiasis, 192 were found to be positive having a prevalence of 48% and mean egg intensity of 12.02 eggs/10 ml of urine. The highest prevalence (57%) was recorded among pupils from Tangwale primary school while pupils from Kaura Kimba and Gidan Bubu primary schools had the least prevalence (40% each) (Table 1).

Table 1 School and class prevalence of Schistosoma haematobium infection among primary school pupils in Wamakko Local Government Area, Sokoto
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It could be seen from Table 2 that males had a higher prevalence (49.49%) than females with a prevalence of 43.93%. The occurrence of S. haematobium did not significantly associate with gender (χ2 = 0.972: df = 1, p = 0.147). Similarly, there was a higher mean egg intensity in males (14.3 egg/10 ml) than in females (4.98 eggs/10 ml). However, statistical analysis indicated no significant difference (p > 0.05) in the mean egg intensity of the pupils with respect to gender (Table 2).

Table 2 Sex and age prevalence of urinary schistosomiasis among primary school pupils in Wamakko Local Government Area, Sokoto
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Pupils aged 4–6 years had the highest prevalence of 62.86%, while pupils aged 7–9 years had the least prevalence of 40.67%. Statistical analysis indicated no association between the occurrence of infection and age group (χ2 = 8.37: df = 3 p > 0.699). On the other hand, the mean egg intensity was significantly (p < 0.05) highest in pupils aged 13 years and above (16.19 eggs/10 ml) while pupils aged 4–6 years had the lowest mean egg intensity (6.50 eggs/10 ml) (Table 2).

It could be seen from Table 3 that pupils who use the river as their source of drinking water had the highest prevalence (100%) while pupils who use well recorded the least prevalence (45.51%). No significant association exists between the occurrence of infection and source of drinking water (χ2 = 4.62: df = 2 p > 0.265). The mean egg intensity was the highest among pupils who use well as their source of drinking water (13.57 eggs/10 ml) while pupils who use river had the least mean egg (6.50 eggs/10 ml). There is no significant difference (p > 0.05) in mean egg intensity with respect to the source of drinking water (Table 3).

Table 3 Prevalence of Schistosoma haematobium among primary school pupils in Wamakko Local Government Area, Sokoto, in relation to the source of drinking water, water contact activity and painful urination (dysuria)
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The prevalence of S. haematobium infection in relation to water contact activity was found to be highest among pupils who visit river to wash (83.33%) while those who do not know their water contact activity had the least prevalence (37.23%). Statistical analysis indicated no significant association between the occurrence of S. haematobium infection and water contact activity (χ2 = 22.6: df = 5 p > 0.81). The mean egg intensity of the infection was the highest among pupils who engage in irrigation farming (25.88 eggs/10 ml) while those who feed animals and those who fetch water both recorded mean egg intensity (2.70 eggs/10 ml). Statistical analysis indicated a significant difference (p < 0.05) between mean egg intensity of pupils with respect to water contact activity (Table 3).

Discussion

The current study showed the occurrence of S. haematobium infection among primary school pupils in Wamakko Local Government, Sokoto State, Nigeria, with an overall prevalence of 48%. The prevalence of 48% recorded in this study is higher than 18.7% reported by Damen, Kopkuk, and Lugos (2018) in North Central Nigeria, 38.3% reported by Kabiru et al. (2013) in Wamakko Local Government, 37.7% reported by Bello et al. (2014) in Wurno Local Government all in Sokoto State, and 32.0% reported by Hassan et al. (2017) in Kebbi State, Northwestern Nigeria. This prevalence reflects the high exposure of the pupils to cercaria-contaminated water bodies.

Findings of this study revealed that S. haematobium infection did not significantly associate with gender. This is in conformity with other findings such as that of Kabiru et al. (2013) in Wamakko Local Government, Sokoto State; Dawet, Benjamin, and Yakubu (2012) in Jos North, Plateau State; and Nwachukwu, Ohaeri, Ukpai, Irole-Eze, and Amaechi (2018) in Ebonyi State, Nigeria. This indicates that both sexes are equally exposed to the source of S. haematobium infection. However, other authors such as Badmos and Komolafe (2007) in Ibadan, Oyo State; Sarkinfada, Azeez-Akande, Isa, and Zubairu (2009) in Kano State; Joseph, Gaji, Muhammad, Baba, and Thilza (2010) in Maiduguri, Borno State; Ladan et al. (2011) in Gusau, Zamfara State; Bello et al. (2014) in Sokoto State; Dawaki et al. (2016) in Kano State; and Hassan et al. (2017) in Kebbi State observed significant association of S. haematobium infection with males.

The lack of significant association of S. haematobium infection with age is an indication that regardless of age, all pupils are equally exposed to cercaria-contaminated water bodies. This agrees with the findings of Joseph et al. (2010) in Maiduguri, Borno State; Dawet et al. (2012) in Jos North, Plateau State; Kabiru et al. (2013) in Wamakko, Sokoto State; Damen et al. (2018) in North Central; and Nwachukwu et al. (2018) in Ebonyi State where they reported no significant association in the occurrence of S. haematobium infection with age. However, Dawaki et al. (2016) in Kano and Hassan et al. (2017) in Kebbi State reported a significant association of S. haematobium infection with age.

Although Kabiru et al. (2013) in Wamakko reported significant association in the occurrence of S. haematobium infection with fishing, findings of this study revealed lack of significant association in the occurrence of S. haematobium infection with water contact activity. This indicates that the schools examined were close to the river, hence frequent exposure of pupils to the source of S. haematobium infection.

The lack of significant association of S. haematobium infection with a source of drinking water shows that all pupils are equally exposed to contaminated water bodies. This agrees with the findings of Dawaki et al. (2016) in Kano. However, Dawet et al. (2012) in Jos North, Plateau State, and Nwachukwu et al. (2018) reported a significant association of S. haematobium infection with a source of drinking water, as a subject who obtain their water from stream was significantly more infected than those who use well.

Conclusion

In conclusion, this study demonstrated that S. haematobium infection was prevalent among primary school pupils in Wamakko Local Government, Sokoto State, and that all pupils in the study area are equally exposed to the sources of S. haematobium infection. Therefore, mass chemotherapy, provision of health education to the communities, provision of safe water supply and sanitation facilities are highly advocated.