BackgroundSchistosomiasis and soil-transmitted helminthiasis (STH) are widely distributed in Cameroon. Although mass drug administration (MDA) of mebendazole is implemented nationwide, treatment with praziquantel was so far limited to the three northern regions and few health districts in the southern part of Cameroon, based on previous mapping conducted 25 years ago. To update the disease distribution map and determine where treatment with praziquantel should be extended, mapping surveys were conducted in three of the seven southern regions of Cameroon, i.e. Centre, East and West.MethodologyParasitological surveys were conducted in April–May 2010 in selected schools in all 63 health districts of the three targeted regions, using appropriate research methodologies, i.e. Kato-Katz and urine filtration.Principal FindingsThe results showed significant variation of schistosomiasis and STH prevalence between schools, villages, districts and regions. Schistosoma mansoni was the most prevalent schistosome species, with an overall prevalence of 5.53%, followed by S. haematobium (1.72%) and S. guineensis (0.14%). The overall prevalence of schistosomiasis across the three regions was 7.31% (95% CI: 6.86–7.77%). The prevalence for Ascaris lumbricoides was 11.48 (95% CI: 10.93–12.04%), Trichuris trichiura 18.22% (95% CI: 17.56–18.90%) and hookworms 1.55% (95% CI: 1.35–1.78%), with an overall STH prevalence of 24.10% (95% CI: 23.36–24.85%) across the three regions. STH was more prevalent in the East region (46.57%; 95% CI: 44.41–48.75%) in comparison to the Centre (25.12; 95% CI: 24.10–26.17%) and West (10.49%; 95% CI: 9.57–11.51%) regions.Conclusions/SignificanceIn comparison to previous data, the results showed an increase of schistosomiasis transmission in several health districts, whereas there was a significant decline of STH infections. Based on the prevalence data, the continuation of annual or bi-annual MDA for STH is recommended, as well as an extension of praziquantel in identified moderate and high risk communities for schistosomiasis.

Although field trials of the application of molluscicides for the control of human schistosomiasis have been conducted in several settings, the acceptability of molluscide use at the community level has been poorly documented. The death and putrefaction of aquatic organisms in water treated with niclosamide (Bayluscide), for example, and the yellowish colouration of such water, may decrease the molluscide's acceptability. It may be possible, however, to use doses of a molluscicide that are only just high enough to kill the target snails but not high enough to kill non-target fish and frogs, thereby reducing the application's impact on water quality and colour and improving its acceptability to local communities. In a study in northern Cameroon, Bayluscide WP70 was applied to ponds at concentrations of 0, 0.25, 0.5 or 1 g/m(3). Changes in human contact with the water in the ponds were explored both by direct observation and by in-depth interviews with key informants from the local community. Although all applications of niclosamide greatly decreased human use of the treated ponds for a few days, most informants (99%) were in favour of niclosamide application and only 6% of the interviewees gave change in water colour or bad smell as a reason for not using a particular water body. Over the few days post-application, use of ponds treated with 0.25 or 0.5 g Bayluscide WP70/m(3) was higher than that of the ponds treated with 1 g/m(3), indicating that relatively low-dose applications, if effective in controlling snails, may be more acceptable to local communities than applications at higher doses.

(Hunter et al. 1996). Snail host control measures are best considered as part of an integrated approach in schistosomiasis morbidity control activities, dominated by population-based chemotherapy (Ripert 2003, Clennon et al. 2004. Molluscicides have been used to control schistosomiasis since the 1950s, but this strategy has been criticized for its high cost and the damage that molluscicides cause to non-target organisms. Bayluscide, the most used synthetic molluscicide is effective against all developmental stages of snails and schistosomes (Tchounwou et al. 1991, 1992, Abu-Elyazeed et al. 1993, Lowe et al. 2005. At molluscicidal concentrations, Bayluscide is lethal to fish unless they can escape to unaffected parts of waterbodies (Evans 1983, Goll et al. 1984. Focal mollusciciding is a cost effective method for schistosomiasis control, particularly in arid regions where transmission sites are small and seasonal (Klumpp & Chu 1987, Sarquis et al. 1997. Bayluscide application following the simplified technique (Greer et al. 1996) is effective at 0.5 g/m 3 , half the recommended dose. The advantage of the simplified technique resides in the fact that heavier doses of the concentrate are applied to the margins of the water bodies where most snail hosts are found. Unfortunately, the death and putrefaction of non-target aquatic organisms such as fish, tadpoles, frogs, and earth worms reduce the acceptability of molluscicide application. The present study was designed to field test whether a lower dose (0.25 g/m 3 ) of Bayluscide would kill fewer nontarget organisms, while maintaining its effect on snail host. MATERIALS AND METHODSThe present investigations were carried out in the locality of Lara in the Mayo Kani Division of the sudanosahelian zone of Cameroon from July to October 1998. This study site was selected for its high prevalence of urinary schistosomiasis, its focal transmission in temporary habitats which are ideal conditions for mollusciciding. During a preliminary visit, health, administrative and village authorities were contacted and explained the goal of the project. Community consent was obtained from the traditional authorities. Ethical clearance was obtained from the Ministry of Health and the Ethical Committee of the Faculty of Medicine & Biomedical Sciences. All study procedures followed were in accordance with the the Helsinki Declaration of 1975, as revised in 1983.In order to assess the effect of Bayluscide on snail populations, water contact sites were identified, test and control ponds randomly assigned. Niclosamide or Bayluscide wettable powder 70% active ingredient (a.i.) was applied to study ponds at concentrations of 0, 0.25, 0.5, and 1 g/m 3 , following the simplified technique. The weight of niclosamide required for each application was derived from estimates of pool volumes assuming that the contours of pools approximated a segment of a sphere. The volume of water in each pond was determined based on a paced measurement of circumference from a standard scale developed earlier (Gree...