The contribution of existing health facilities to the control of urinary schistosomiasis in northern Cameroon.

This paper attempts to analyse the impact of the regular functioning of existing health services on the control of urinary schistosomiasis in two villages in northern Cameroon. The health centres' diagnostic systems selectively recognise heavy infections. The efficacy of reaching and subsequently treating heavily infected subjects, however, is low. No more than around 5% of the heavily infected subjects in the health centres' catchments areas is reached on an annual basis. Further analysis shows that the percentage of infected and heavily infected subjects is not higher among the visitors of the health centre than in the inhabitants of the villages involved. Heavy infection is not a reason to visit the health centre, in these villages. To increase the role of the existing health structure in coping with Schistosoma haematobium infections, the diagnostic system, used in the health centres, could be improved by a standardized inclusion of laboratory examination of clinically suspected individuals. Simultaneously, the awareness of the infected population to respond to infection by visiting the health centre needs further development.

An attempt to quantify the role of existing health facilities in controlling vesical schistosomiasis in rural northern Cameroon.

Around the artificial reservoir in the Benue River near Lagdo in Northern Cameroon, Schistosoma haematobium and S. mansoni are prevalent. The primary health care structure has been reinforced in recent years, but no special attention has been paid to schistosomiasis. This setting was considered ideal to estimate the contribution of the existing health facilities in the control of morbidity due to schistosomiasis. The patients locally diagnosed as having vesical schistosomiasis, were subsequently examined with a standardized quantitative filtration method. Furthermore, surveys were carried out in the surrounding villages to estimate the age-specific prevalences of vesical schistosomiasis in the health centre's catchment area. The number of heavily infected people is low in the region (12%), but heavy infections represented 64% of the visitors with vesical schistosomiasis at the health centre. The data suggest that the health centre is efficacious in 'passively' detecting the most heavy infections. It was also possible to identify villages with large numbers of heavily infected people from the health centre's records. Finally, a calculation model is presented to estimate the expected number of visitors to the health centre, based on data from the field survey.

Prey selection by molluscivorous cichlids foraging on a schistosomiasis vector snail, Biomphalaria glabrata.

This paper considers prey size selection by four molluscivorous cichlids feeding on the intermediate host snail of Schistosoma parasites, Biomphalaria glabrata. Haplochromis ishmaeli obtains its prey by crushing the snails between the pharyngeal jaws, whereas H. xenognathus, H. sauvagei and Macropleurodus bicolor apply both pharyngeal crushing and oral shelling. The fishes crushed significantly more snails with the highest reward in biomass per second of crushing. Oral shelling occurred far less often than pharyngeal crushing. Encounter rates with prey showed significant variations between different size classes of prey. The fish have no overall knowledge of snail availability in a tank. The probability that a snail will be eaten at encounter, calculated from the number encountered and the number eaten, reflects the prey size preference of the fish. Those snails with the highest biomass/crushing-time ratio had the highest probability of being crushed; observed and predicted prey size preferences corresponded well. Although for oral shelling the potential reward in biomass per second is of the same magnitude as for crushing, the probability of successful shelling is very low. Apparently the fish prefer prey with lowest risks.