The current epidemiological status of urogenital schistosomiasis among primary school pupils in Katsina State, Nigeria: An imperative for a scale up of water and sanitation initiative and mass administration of medicines with Praziquantel
[['Human schistosomiasis , though less fatal , but debilitating and chronic in nature , is among a set of 17 neglected tropical infectious diseases of poverty that is currently posing a threat to the wellbeing of 2 billion people in the world [1] .', 'The aetiological agent of urogenital schistosomiasis is the infective stage ( cercaria ) of Schistosoma haematobium , a digenetic trematode plathyhelminth whose intermediate hosts are some species of gastropod snails in the genus Bulinus [2 , 3] .', 'Maturity of S . haematobium worms takes place at the portal vein of a human host .', 'Subsequently , each male worm carries a female partner in its genaecophoric canal to the veins of the pelvis where the latter lays a very large number of eggs equipped with terminal spines .', 'Consequently , they rupture the endothelial linings of the vesical and urethral walls , leading to granulomatous inflammation , ulceration , pseudopolyposis , and haematuria [4–6] .', 'As a result of its associated morbidities , an estimate of 280 , 000 people die annually from human schistosomiasis [7] .', 'Currently , sub-Saharan Africa ( SSA ) is regarded as the poorest part of the world with 73% of its population living on USD 2 per day [8] .', 'This index of abject poverty is of no doubt a key player in the reported astounding 112 million cases of urogenital schistosomiasis ( less than a decade ago ) out of the 203 . 15 million ( 85% of global figure ) active cases of human schistosomiasis in the region [9 , 10] .', 'Schistosomiasis was reportedly transmitted into the Northern part of Nigeria by invading Fulani herdsmen from upper Nile valley in the ancient times [11] .', 'However , documented evidence was not obtained until 1881when a German immigrant , Gustav Nachtigal , commented on a high incidence of haematuria in Borno , a northeastern State of Nigeria close to Lake Chad [12] .', 'In 1963 , the first map showing the distribution of schistosomiasis in Nigeria was produced by Professor Cowper [13] .', 'Currently , Nigeria has 29 million cases of schistosomiasis , the highest in SSA , with 101 . 3 million people living in close proximity to various endemic foci [14] .', 'The endemicity of schistosomiasis was ascertained in Katsina State as far back as 1963 when prevalences of 95% and above 90% were recorded in Katsina and Kankia Local Government Areas [12] .', 'In 2010 , UNICEF signed a contribution agreement with the Government of United Kingdom and Northern Ireland to implement Sanitation , Hygiene and Water in Nigeria ( SHAWN ) between March 2014 and November 2018 .', 'Among others , the initiative aims at providing Water , Sanitation and Hygiene ( WASH ) facilities for 3 , 500 schools and 1 , 200 health centers .', 'The benefit of this initiative is that pupils would have the capacity to promote personal , domestic , and environmental cleanliness .', 'Invariably , schistosomiasis control programme will be enhanced because the risk of contracting the disease will be drastically reduced to the barest minimum .', 'However , only 11 out of 34 LGAs in Katsina State were supported by the SHAWN initiative as at February 2015 [15] .', 'The SHAWN/ WASH initiative vis a vis Mass Administration of Medicines ( MAM ) with Praziquantel ( PZQ ) in Katsina State require epidemiological data to achieve their aims .', 'Nonetheless , there is limited information in the literature about the current epidemiological status of urogenital schistosomiasis among Primary School pupils in Katsina State .', 'Therefore , we embarked on this study with the aim of investigating the prevalence , intensity and risk factors of urogenital schistosomiasis in the study area .'], ['Dutsin-Ma Local Government Area ( LGA ) [12 . 45°N and 7 . 50° E] is located in the eastern part of Katsina State in North western part of Nigeria .', 'It covers a total surface area of 527 km2 and is inhabited by a population of 169 , 829 people as at 2006 National Census [16] .', 'It is predominantly inhabited by Hausa-Fulani tribes whose major occupations are trading , farming , and animal rearing .', 'With a characteristic tropical continental climate type , Dutsin-Ma LGA ( see Fig 1 ) has a temperature range of 29─31°C and mean annual rainfall of 700mm which commences in May and ends by September [17] .', 'As a result of these , its soil is typically sandy and shallow , supporting only cereals like sorghum , millet and grasses .', 'However , short , drought-resistant and scattered trees are present .', 'This vegetation type makes the study area most suitable for pastoralists .', 'Dutsin-Ma is a rural area characterized with a poor network of healthcare facilities .', 'Generally , potable water is not readily available to average inhabitant of the area .', 'Residents depend on water from unwholesome sources like dams , lakes , and ponds .', 'On the average , a Mono pump , where available , serves over 30 households .', 'In the study area , MAM with Praziquantel ( PZQ ) was last carried out in December , 2014 .'], ['In this study , a total number of 491 primary school pupils with age range of 6─15 years were recruited from 5 communities in Dutsin-Ma Local Government Area of Katsina State .', 'The mean age ± standard deviation ( S . D ) was 9 . 57 ± 2 . 14 years and 40 . 29% were females .', 'However , 7 of these pupils did not submit urine samples following interview with questionnaires ( see Fig 2 ) .', 'Of noteworthy are the facts that 88 . 64% had lived in the study area for more than 4 years; 60 . 33% lived more than 100m away from potentially infested open water sources; only 5 . 37% had a previous access to Praziquantel while 13 . 08% and 50 . 81% reportedly experienced macrohaematuria and dysuria respectively .', 'Level of illiteracy among mothers of the respondents doubled that of their fathers while access to tertiary education in their fathers almost doubled mothers’ .', 'The most common paternal occupational category was “brown collar jobs while mothers of respondents were majorly housewives ( see Table 1 ) . The results about knowledge , attitudes and health-seeking practices of the respondents about urogenital schistosomiasis are shown in Table 2 . It was found that 426 ( 88 . 02% ) and 405 ( 83 . 68% ) , a majority had the awareness of urogenital schistosomiasis ( locally called tsagiyya or sarajini ) and the snail intermediate host respectively . Meanwhile , the prevalence of the disease was found to be significantly associated with knowledge about the snail host ( χ2 = 4 . 23; P = 0 . 0398 ) . Of the total number of respondents , 46 ( 9 . 50% ) had visited health facilities , 18 ( 3 . 72% ) opted for traditional healing , while 37 ( 7 . 64% ) received no medication for urogenital schistosomiasis . The results displayed in Table 3 showed that urogenital schistosomiasis was significantly associated with water contact activities for domestic , recreational and farming purposes ( χ2 = 25 . 788; P = 0 . 0001 ) . Respondents who indulged in the habit of swimming for recreation recorded the highest prevalence of 24 . 59% ( 17 . 20─33 . 20 ) while being 3 times more likely to be infected with urogenital schistosomiasis compared with those who only had contact with closed , non-infested water sources [COR ( 95% CI ) : 3 . 39 ( 2 . 01─5 . 72 ) ] . Those who combined swimming with play in shallow waters had the second highest prevalence ( see Fig 3 ) of 23 . 36% ( 15 . 70─32 . 50 ) and as well 3 times more likely to be infected [COR ( 95% CI ) : 3 . 18 ( 1 . 82─5 . 49 ) ] . Nonetheless , those who combined open and closed water sources , against expectation , recorded the highest mean intensity of the infection [27 . 83 ( 15 . 78─49 . 09 ) eggs/ 10ml of urine sample] followed by respondents with experience of water contact by irrigation [26 . 92 ( 12 . 92─56 . 08 ) eggs/ 10ml of urine sample] . Results of Table 4 convincingly show that gender ( χ2 = 16 . 722; P = 0 . 0001 ) ; age ( χ2 = 9 . 589; P = 0 . 0019 ) ; economic status of school attended ( χ2 = 4 . 869; P = 0 . 0273 ) ; residence distance from open water sources ( χ2 = 10 . 546; P = 0 . 0012 ) ; mothers’ occupational ( χ2 = 6 . 081; P = 0 . 0137 ) and educational status ( χ2 = 4 . 139; P = 0 . 0419 ) were additional determinant factors of urogenital schistosomiasis in the study area . In this study , the overall Prevalence and Arithmetic Mean Intensity of the infection were 8 . 68% ( 6 . 39─ 11 . 64 ) and 80 . 09 ( 30 . 92─129 . 28 ) eggs per 10ml of urine . Of the 42 respondents infected , 27 ( 64 . 29% ) belonged to the ‘light intensity’ status while 15 ( 35 . 71% ) fell to the ‘heavy intensity’ category . Highest values of prevalence were obtained in: males: 90 . 48% ( 77 . 38─ 97 . 34 ) ; age group 11─15: 54 . 76% ( 38 . 70─70 . 20 ) ; public schools: 88 . 09% ( 74 . 40─96 . 00 ) ; respondents whose residence distance are < 100m from open water sources: 64 . 29% ( 48 . 03─78 . 45 ) ; those with brown collar jobs as fathers’ occupation: 61 . 90% ( 45 . 64─76 . 43 ) ; respondents whose mothers were housewives: 59 . 52% ( 43 . 28─74 . 37 ) ; and respondents whose fathers: 50 . 00% ( 34 . 19─ 65 . 81 ) and mothers: 54 . 76% ( 38 . 67─70 . 15 ) attained secondary level of education . Similarly , highest mean intensities of urogenital schistosomiasis were recorded in age group 11─15: 36 . 37 ( 18 . 25─72 . 47 ) eggs per 10ml ( see Fig 4 ) ; respondents whose mothers were housewives: 31 . 43 ( 16 . 30─60 . 61 ) eggs per 10ml; and respondents whose fathers attained secondary level of education: 41 . 34 ( 20 . 99─81 . 39 ) eggs per 10ml . However , contrary to expectation , highest mean intensities of the infection were recorded in females: 33 . 01 ( 2 . 88─378 . 16 ) eggs per 10ml; private schools: 76 . 19 ( 23 . 28─249 . 34 ) eggs per 10ml; respondents whose residence distance were ˃ 100m from open water sources: 28 . 97 ( 12 . 23─68 . 62 ) eggs per 10ml ( see Fig 4 ) ; those with white collar jobs as fathers’ occupation: 42 . 08 ( 15 . 55─113 . 85 ) eggs per 10ml and respondents whose mothers attained tertiary level of education: 255 . 15 ( 0 . 00─9 . 46e+07 ) eggs per 10ml . Table 5 presents data on the strength of association between urogenital schistosomiasis and determinant factors that were found to be significantly associated with it . Male respondents were discovered to be 7 times [AOR ( 95% CI ) : 7 . 23 ( 2 . 54–20 . 60 ) ] more likely to be infected with the cercariae of S . haematobium compared to their female counterparts . Age group 11–15 years [AOR ( 95% CI ) : 2 . 81 ( 1 . 48–5 . 34 ) ] , respondents from public school sector [AOR ( 95% CI ) : 2 . 82 ( 1 . 15─8 . 25 ) ] and those living < 100m from open , infested water sources [AOR ( 95% CI ) : 3 . 02 ( 1 . 56─5 . 85 ) ] were found to be about 3 times more likely to be infected compared to others in their respective categories . In Mothers’ occupation category , respondent with “other brown collar jobs” [AOR ( 95% CI ) : 8 . 66 ( 1 . 13─66 . 49 ) ] and “housewives” as mothers’ occupation [AOR ( 95% CI ) : 8 . 85 ( 1 . 18─66 . 33 ) ] were about 9 times more likely to be infected compared to those whose with “white collar jobs” as mothers’ occupation .', 'It is puzzling that respondents whose mothers attained secondary level of education were 6 times [AOR ( 95% CI ) : 6 . 09 ( 1 . 40─26 . 45 ) ] more likely to be infected compared to those whose mothers attained a tertiary education level .', 'With respect to the risk of infection with S . haematobium , males who lived in the study area were found to be 6 times more at risk than females [RR ( 95% CI ) : 6 . 41 ( 2 . 33─17 . 67 ) ] .', 'In similarity to the odd of infection , age group 11–15 years [RR ( 95% CI ) : 2 . 55 ( 1 . 43─4 . 53 ) ] , respondents from public school sector [RR ( 95% CI ) : 2 . 63 ( 1 . 06─6 . 55 ) ] and those living < 100m from open , infested water sources [RR ( 95% CI ) : 2 . 74 ( 1 . 49─5 . 01 ) ] were found to be about 3 times more at risk of being infected compared to others in their respective groups .', 'Respondent with “other brown collar jobs” [RR ( 95% CI ) : 7 . 90 ( 1 . 07─58 . 51 ) ] and “housewives” [RR ( 95% CI ) : 8 . 06 ( 1 . 11─58 . 54 ) ] as mothers’ occupational categories were about 8 times more at risk of being infected compared to those with “white collar jobs” as mothers’ occupation .', 'The results of our multivariate analysis further showed that subjects whose mothers attained secondary level of education were 5 times [RR ( 95% CI ) : 5 . 48 ( 1 . 32─22 . 72 ) ] more at risk of being infected compared to those whose mothers attained a tertiary level of education .', 'Finally , subjects who suffered macrohaematuria were found to be about 2 times [RR ( 95% CI ) : 1 . 72 ( 1 . 04─2 . 85 ) ] more at risk of contracting urogenital schoistosomiasis compared to those who experienced dysuria .'], ['The concept of IDM was devised less than two decades ago to act as a “catalyst” in the control strategies of diseases that are proving difficult to eliminate although effective tools are available .', 'The fundamental principle of this intervention is to ensure that barriers to control strategies are destroyed using the level of awareness about the disease in the population at risk , knowledge of the current epidemiological status of the disease , and the availability and efficacy of available medicines , vaccines and diagnostic tools among others [22] .', 'In the context of this study , knowledge about haematuria and Bulinus spp .', 'was used as a strong indicator of awareness about urogenital schistosomiasis .', 'Our findings showed that 426 ( 88 . 02% ) of the school children surveyed had a knowledge of the disease through the local name for haematuria , tsagiyya , while 405 ( 83 . 68% ) , had the awareness of the snail intermediate host .', 'The latter was significantly associated with the disease ( see Table 2 ) .', 'The logicality of these findings cannot be subjected to a doubt because infection with the cercariae of S . haematobium is practically impossible without a transmission cycle involving the suitable snail intermediate host .', 'The strong association clearly suggests that infected respondents most likely came across the snail intermediate host while swimming , bathing , fishing , and/or fetching water in infested streams , rivers , ponds , lakes , and so on .', 'Hunting snails in aquatic terrains might also have been responsible for this .', 'In summary , the cause of this association could be linked to a significant contact ( with the snail host versus its aquatic medium ) that was enough to encourage transmission of the disease .', 'This knowledge about the snail intermediate host is a strong boost because SAC could be integrated into future control programmes for the disease with the aim of targeting the snails with molluscicides .', 'Besides , physical control measure by handpicking could be enhanced .', 'Our results on the knowledge of the current epidemiological status of urogenital schistosomiasis showed that the prevalence and arithmetic mean intensity of the disease were 8 . 68% ( 6 . 39─11 . 64 ) and 80 . 09 ( 30 . 92─129 . 28 ) eggs per 10ml of urine sample respectively ( see Table 4 ) .', 'It is obvious that the study area is hypo-endemic ( prevalence < 20% ) for urogenital schistosomiasis [23] while , based on the arithmetic mean of 80 . 09 ( 30 . 92─129 . 28 ) eggs per 10ml of urine sample , an average infected respondent had a heavy intensity of infection .', 'As expected , male respondents had higher prevalence ( 90 . 48% Vs 9 . 52% ) and mean intensity of infection ( 81 . 87 Vs 63 . 25 ) .', 'We also showed through the adjusted Odds Ratio that for every female respondent infected , seven males were infected .', 'Previous studies have reported higher odds of infection with S . haematobium in male students [24–26] .', 'Meanwhile , previous findings have shown that increase in intensity of infection with urogenital schistosomiasis increased the risk of Female Genital Schistosomiasis ( FGS ) evidenced by cervical inflammation , intraepithelial neoplasia , postcoital bleeding and genital ulceration [27] .', 'This has been identified as a risk factor in Human Immuno-deficient Virus ( HIV ) transmission to women [28] .', 'In males , genital schistosomiasis has been reported to induce pathology of the seminal vesicles and the prostate with irreversible long-term consequences which may culminate in bladder cancer , urethral fibrosis and hydronephrosis [28] .', 'Studies have also shown that such high infection intensities make eggs of schistosomes to be trapped in tissues of the liver , spleen and peritonium with severe and complex pathological consequences which may degenerate to late-stage sequelae .', 'Besides , school-age children suffer academic setbacks as well as Iron status deterioration .', 'Organs damaged may not recover until at least six months after cure with Praziquantel [21] .', 'The Risk Ratio obtained from this study revealed that male inhabitants of the study area were six times more at risk of infection with urogenital schistosomiasis ( see Table 5 ) .', 'This could be explained by the already known fact that boys are more involved in water contact activities like swimming , fishing , playing in shallow water , irrigation , and making of bricks to build mud houses than girls .', 'Currently , there are no vaccines against S . haematobium .', 'However , there exist effective diagnostic tools and chemotherapeutic intervention with PZQ , the global drug of choice [21 , 29] .', 'Apart from the gold diagnostic standard of microscopy [29–31] , a rapid , non-invasive dipstick called Medi-Test , though expensive but readily available in capital cities of Katsina State , was used for the survey as stated earlier .', 'The study area is known for some spurious sentiments about MAM and Public Health survey .', 'Consequently , chemotherapeutic interventions are sometimes seen as attempt to render females infertile .', 'Sometimes , physical attacks with weapons are launched at researchers/ healthcare workers [24] .', 'This probably informed the low PZQ coverage of 5 . 37% recorded in this survey .', 'As a matter of fact , the record we had on our school-based questionnaires showed that three of the five schools surveyed did not benefit from the previous MAM carried out in 2014 .', 'One of the other two who benefitted claimed to have distributed it but response from the pupils during interview negated such claim .', 'It was also likely that it was not done due to the fear of stiff resistance from the mostly uneducated misinformed and indoctrinated parents .', 'The juxtaposition of this peculiar challenge with the fact that Nigeria ranks number three globally among the countries in most urgent need of chemotherapeutic intervention [22] shows there is still a long way to go to achieving the roadmap for the control of schistosomiasis .', 'Water , sanitation and hygiene ( WASH ) have been identified as part of the key factors determining the state of health in any epidemiological settings [22] .', 'The implication of this is that poor or no access to potable water supply tend to contribute to high prevalence and mean intensity of infection with urogenital schistosomiasis .', 'Our findings in this present study proved this to be true .', 'It showed that respondents who had experience of swimming recorded the highest prevalence , followed by those who combined both the recreational activities of swimming and playing in shallow water .', 'Those who were involved in farm-related activities of fishing had the third placed prevalence .', 'Respondents who combined open , potentially infested with closed water sources recorded the highest mean intensity of the infection , being closely trailed by those who came into contact with open , unwholesome water through the activity of irrigation .', 'Generally , respondents whole came into contact with open water sources like rivers , ponds , streams and lakes were two or three times more likely to be infected with the infective larval form of S haematobium ( see Table 3 ) compared to their counterparts who had contact with well , tap water , bore hole and sachet water ( closed water sources ) .', 'We stated earlier that only 11 out of 34 LGAs in Katsina State were covered by the SHAWN as at February 2015 .', 'This report vis a vis the data obtained in this present survey ( more importantly; the heavy mean intensities of infection ) pointed to the fact that the initiative has a long way to go in view of its deadline of November 2018 given to round up its intervention in the Nigerian State .', 'Extrapolation of our findings to the whole communities in the study area will amount to painting a wrong epidemiological picture of urogenital schistosomiaisis [23] partly because of its age-sensitivity and focal nature .', 'To corroborate this , previous studies among high school children have identified the study area as being at “moderate-risk” for the disease [24 , 25 , 32] as opposed to the “low risk” reported in this present study involving primary school pupils .', 'This study employed urine centrifugation technique for egg concentration due to a lack of polycarbonate filters that would have provided a better picture of mean intensity of infection .', 'Thus , it is likely that the mean intensity of urogenital schistosomiasis in this survey is under-reported here .', 'The overall prevalence obtained in this survey shows that the study area was at a low-risk degree of endemicity for urogenital schistosomiasis .', 'Beneath this is the subtle , latent and deadly morbidity-inducing heavy mean intensity of infection which encompassed all determinant ( risk ) factors identified in this study , thus calling for urgent intervention .', 'Based on these premises , we uphold the recommendation of Crompton & World Health Organization ( WHO ) on the execution of chemotherapeutic intervention with PZQ twice for School-Age Children ( enrolled or not enrolled ) during their primary schooling age ( once each at the point of admission and graduation ) in the study area [33] .', 'We deemed it fit that , as in the case of loiasis , an NTD , the criteria for classifying endemic areas for schistosomiasis be reviewed to capture the magnitude of mean intensity of infection rather than prevalence only as this may underplay its epidemiological severity .', 'While concluding that SHAWN/WASH and MAM programmes in the study area are seriously lagging behind as evidenced in our findings , we strongly recommend that the State Government vis a vis Non-Governmental Organizations ( NGOs ) , as a matter of urgency , form a problem-solving alliance to provide water , sanitation and hygiene facilities as well as PZQ with appropriate networking to the grass-root level .', 'Health education should also be carried out at the grass-root level to create awareness about the various factors that predispose people to the infection .']]
['Introduction', 'Materials and methods', 'Results', 'Discussion']
['Human schistosomiasis , a debilitating and chronic disease , is among a set of 17 neglected tropical infectious diseases of poverty that is currently posing a threat to the wellbeing of 2 billion people in the world .', 'The SHAWN/WASH and MAM programmes in the study area require epidemiological data to enhance their effectiveness .', 'We therefore embarked on this cross-sectional study with the aim of investigating the prevalence , intensity and risk factors of urogenital schistosomiasis .', 'Interviewed 484 respondents produced terminal urine samples ( between 10 . 00h – 14 . 00h ) which were analyzed with Medi ─Test Combi 10 and centrifuged at 400 r . p . m for 4 minutes using C2 series Centurion Scientific Centrifuge .', 'Eggs of S . haematobium were identified with their terminal spines using Motic Binocular Microscope .', 'Data were analyzed with Epi Info 7 .', 'In this study , the overall prevalence and arithmetic mean intensity of the infection were 8 . 68% ( 6 . 39─ 11 . 64 ) and 80 . 09 ( 30 . 92─129 . 28 ) eggs per 10ml of urine respectively .', 'Urogenital schistosomiasis was significantly associated with knowledge about the snail host ( χ2 = 4 . 23; P = 0 . 0398 ) ; water contact activities ( χ2 = 25 . 788; P = 0 . 0001 ) , gender ( χ2 = 16 . 722; P = 0 . 0001 ) ; age ( χ2 = 9 . 589; P = 0 . 0019 ) ; economic status of school attended ( χ2 = 4 . 869; P = 0 . 0273 ) ; residence distance from open water sources ( χ2 = 10 . 546; P = 0 . 0012 ) ; mothers’ occupational ( χ2 = 6 . 081; P = 0 . 0137 ) and educational status ( χ2 = 4 . 139; P = 0 . 0419 ) .', 'The overall prevalence obtained in this survey shows that the study area was at a low-risk degree of endemicity for urogenital schistosomiasis .', 'Beneath this is a subtle , latent and deadly morbidity-inducing heavy mean intensity of infection , calling for urgent implementation of WHO recommendation that MAM with PZQ be carried out twice for School-Age Children ( enrolled or not enrolled ) during their primary schooling age ( once each at the point of admission and graduation ) .', 'The criteria for classifying endemic areas for schistosomiasis should also be reviewed to capture the magnitude of mean intensity of infection rather than prevalence only as this may underplay its epidemiological severity .']
['In 1851 , human schistosomiasis was discovered in Egypt by a German surgeon named Theodor Bilharz .', 'Therefore , it is alternatively called ‘bilharziasis’ .', 'Being a disease that is closely associated with poverty in the tropics , chiefly the sub-Saharan Africa , Urinary Schistosomiasis is transmitted to humans who source for non-potable water in open and unwholesome water bodies infested with the infective stage of schistosomes which are excreted by Bulinus globosus , a freshwater snail and suitable intermediate host .', 'Before now , many endemic foci of the disease have been discovered with many unidentified yet .', 'Meanwhile , the initiative on Sanitation , Hygiene and Water in Nigeria ( SHAWN ) in the study area is suffering a major setback due to poor data availability despite being due to round up her activities by early 2018 .', 'Consequently , we embarked on this survey to determine: the extent at which Urinary Schistosomiasis is prevalent , its severity , and factors that were responsible for its transmission .', 'We found out that the study area was at a low-moderate risk of endemicity for the disease .', 'However , mean intensity of infection was too high .', 'Based on these , a need for Praziquantel is indisputable .', 'Criteria for categorizing areas endemic for the disease should be revised to embrace the novelty of capturing mean intensity of infection .']
['schistosoma', 'invertebrates', 'medicine and health sciences', 'body fluids', 'education', 'helminths', 'sociology', 'tropical diseases', 'social sciences', 'parasitic diseases', 'animals', 'health care', 'urine', 'gastropods', 'neglected tropical diseases', 'sanitation', 'snails', 'urogenital schistosomiasis', 'public and occupational health', 'schistosoma haematobium', 'schools', 'molluscs', 'people and places', 'helminth infections', 'schistosomiasis', 'environmental health', 'professions', 'eukaryota', 'anatomy', 'physiology', 'biology and life sciences', 'population groupings', 'organisms']