The self-reported uptake of praziquantel among school-age children increased from 28.2% to 48.9% between the two surveys. There was no change in prevalence and intensity of S. mansoni infection as well as in levels of knowledge on schistosomiasis transmission and control and occurrence of side effects attributable to uptake of praziquantel.
Although the increase in uptake of praziquantel was statistically significant, it is unlikely to have public health impact as observed by the persistent high prevalence and intensity of infection with schistosomiasis in the schools. The observed increase in self-reported uptake may be attributable to the high level of engagement between the district health team and the teachers during MDA as well as the provision of incentives including facilitation allowances and T-shirts to the school teachers prior to MDA. Such incentives have been found useful in motivating drug distributors
. In addition, improvement in self-reported uptake could have been as a result of a more intensive follow-up by the district health team and the presence of researchers in the schools during the pre-visits and drug distribution. Such measured improvements in an aspect of behaviour due to the subjects’ awareness that they are being studied, the so-called “Hawthorne effect”, have been reported in other studies
[19, 20]. It is worrying that schools with moderate uptake at baseline did not improve and even declined at follow-up. A possible explanation is that concerted efforts to improve uptake, such as the supervision of teachers by the district health team during MDA, were concentrated on schools with very low uptake at baseline. This observation suggests that modification of the conventional school-based MDA programs may possibly improve drug uptake and further studies are needed to test this hypothesis.
The efficacy of praziquantel against S. mansoni infection is indisputable
[3, 8, 21–23]. With improved uptake, one would expect a reduction in prevalence and intensity of the infection. Indeed, significant reductions in prevalence were observed in schools (4, 5 and 6) with high uptake levels. It is important to note that this is not a cohort study which follows the same children from baseline to follow-up. In the present study, the two study populations in the two different time-points are not completely identical. The persistent high infections despite the increased uptake of praziquantel could be attributable to the fact that the realized level of uptake is lower than is recommended by the WHO and apparently too low to affect the prevalence and intensity of schistosomiasis among the children. Another factor that could have contributed to the sustained high prevalence and intensities of infection despite the increase in uptake level is that praziquantel is not effective against juvenile schistosomes
. The observed eggs may have been a result of immature schistosomes developing into egg laying adult worms during the follow-up period. In this study, 67% of the schools are located within a 5 km radius from lake victoria. Children from schools located closer to the lake frequently visit the lake to fetch water, bathe, to wash, and to swim
 and therefore get infected with schistosomiasis when they get into contact with contaminated water. This explains the variations in prevalence and geometric mean intensity across the different schools.
The fear of side effects of praziquantel, lack of knowledge about schistosomiasis transmission and prevention and lack of teacher support to take preventive treatment were highlighted as some of the major factors associated with the low uptake among school-age children as reported in the ealier paper from this study
. In the follow-up of this study, approximately 50% of the children who received treatment reported to have developed side effects and as such, resistance to swallow the treatment is perhaps inevitable as majority indicated that they would not swallow the drug during the subsequent MDA. Praziquantel causes transient side-effects of the gastro-intestinal and central nervous system including abdominal pain, nausea, vomiting, diarrhea, headache and dizziness, especially when the drug is taken on an empty stomach
[23, 26, 27]. To mitigate the side-effects, the drug should be taken with food
. However, most children in rural areas do not take any meals while at school
 and some take treatment on empty stomachs and experience the side-effects
[2, 22, 29]. Considerable reduction in occurrence of side-effects has been reported in countries where praziquantel was administered with food
[2, 10]. Therefore, implementing measures for mitigating the side effects attributable to praziquantel, such as providing food during MDA, may improve uptake of the drug among school children. High coverage of praziquantel treatment among school children was achieved by the national control program in Sierra Leone, where a special feeding program for the children to mitigate the side effects was provided
Knowledge of schistosomiasis transmission and control was evidently lacking in more than 50% of the children interviewed, a manifestation of the insufficient health education provided prior to and during MDA. During MDA, distribution of praziquantel takes precedence with diminutive, if any, health education on the infection transmission and control. In the absence of this knowledge and with lack of a clear understanding of the rationale of preventive treatment, there is a risk that the targeted populations may resist the treatment
[16, 30]. Improved compliance to treatment for schistosomiasis has been reported among school children with adequate knowledge of schistosomiasis transmission and prevention
[11, 30–32]. In this study, there was a considerable variation in levels of knowledge of schistosomiasis transmission and prevention across the primary schools that ranged from 12.8% to 73.2% at baseline and from 27% to 69% at follow-up. This variation in levels of knowledge of schistosomiasis transmission and prevention could explain the differences in uptake levels of treatment, and prevalence and intensity of infection across the primary schools in the two different time-points. Health education programs for providing school children with information about transmission and prevention are required if sustained drop in prevalence and intensity of S. mansoni infection among school children is to be achieved. It is urged that with chemotherapy, prevalence and intensity of decrease when health education is concurrently implemented
The lack of a comparison group makes it difficult to attribute the observed increase in uptake to strengthened supervision and teacher motivation strategy. Moreover, because data on self-reported uptake were derived from interviews, it is possible that the children could have provided desirable answers. However, the comparison of our findings with those of previous studies in other settings lend credibility to our observations and suggest that the observed increase in uptake could have ensued from the strengthened supervision by the district health team and teacher motivation to distribute the drugs
[32, 33]. The second limitation is the relatively low intrinsic capacity of the Kato-Katz technique to recover parasite eggs from specimens of low infection intensities compared to other parasitological methods
[34, 35]. To increase its sensitivity during the study, two samples were taken from each child and two slides were prepared per fecal sample.