Field trials of low dose Bayluscide on snail hosts of schistosome and selected non-target organisms in sahelian Cameroon

Abstract

(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...

Systematic Review and Meta-analysis of the Impact of Chemical-Based Mollusciciding for Control of Schistosoma mansoni and S. haematobium Transmission

“…The median and most common dose target in our included studies was 1 mg/L, consonant with the experience summarized by Andrews, et al in their detailed 1983 review [ 46 ]. Immediate impact of mollusciciding was usually assessed at breeding sites 24 h after delivery [ 52 ], and then if living snails were still present, reapplication of chemical, sometimes at higher concentrations [ 53 ], was frequently used to maximize snail suppression. Where drip feed administration was applied to running streams, significant molluscicide effects on snail numbers were detectable 900 meters [ 54 ], 1375 meters [ 55 ], 1700 meters [ 40 ], even up to 10 km [ 38 ] downstream.…”

Community acceptability of the use of low-dose niclosamide (Bayluscide®), as a molluscicide in the control of human schistosomiasis in Sahelian Cameroon

“…It remains unclear whether it is the clouding of the treated water caused by the death and putrefaction of aquatic animals (both 'target' and 'non-target'), the yellowish colouration caused by the molluscide itself and/or some other perceived risk that deters local communities from using water bodies recently treated with Bayluscide in the same way that they use untreated water bodies. Since, in terms of their effects on the target snails, the lower doses of Bayluscide appeared as effective as the highest dose tested, they are to be preferred (Takougang et al, 2006). Given that the present study was conducted in an area with endemic urinary schistosomiasis, it was disappointing to see this disease mentioned by only two of the interviewees as a possible reason for not using a particular water body.…”

“…Another four ponds were left untreated, as controls. [When checked 24 h after molluscicide application, all of the snails in the ponds treated with Bayluscide appeared to be dead (Takougang et al, 2006)]. …”

“…Although application of this niclosamide-based molluscicide at 0.5 g/m 3 produces a significant reduction in snail populations, it also results in the death and putrefaction of several non-target aquatic organisms, including fish, amphibians and earthworms (Takougang et al, 2006), and this could deter people from using treated water bodies. The relatively high toxicity of Bayluscide to freshwater snails is one of the reasons why it has been recommended as the molluscicide of choice for the control of snail hosts of schistosomes (Tchounwou et al, 1991).…”

A laboratory assessment of the potential molluscicidal activity of some Nigerian plant species used as anthelmintics

“…Their use is, however, constrained by high costs and toxicities to non-target aquatic biota (McCullough 1992, Pieri et al 1995, Yi et al 2005, Takougang et al 2006. These have given impetus to the continued search for suitable alternatives from indigenous plants, many of which have been found to be toxic not only to the snails that transmit schistosomiasis but also to those transmitting other important parasites of humans.…”