Characterisation of the Chemoreception Niche of Biomphalaria Pfeifferi as an Aid to the Development of Slow - Release Molluscicides.

Abstract

The behavioural responses of the schistosome host snail Biomphalaria pfeifferi to 40 naturally occurring (crude and semi - processed) plant products were studied using diffusion olfactometers. Out of the 40 plant products, 21 were tested in the raw (unprocessed) states, 3 were boiled, 4 were dried and 12 were fermented. Seven (7) out of the 21 raw plant product (33.33%) acted as significant attractants/ arrestant for the adult snails while 6 emerged statistically significant attractants / arrestant for the juveniles. Also 2 (9.52 %) exhibited significant repellent effects on the juveniles. On the whole, the adults were more responsive to the test materials than the juveniles One each (33.33%) of the boiled products acted as a statistically significant attractant for both the adult and juvenile snails. None of the boiled products exhibited repellent effects. For the dried products, none (0%) had any significant effects on the adult snails; however, only dried lettuce (25%) exhibited significant attractant effects on the juveniles. Five of the 12 fermented products had statistically significant repellent effects with none having any significant attractant effects on the adult snails. In the case of the juveniles however, 3 day fermented cassava was the only attractant while 3 products elicited statistically significant repellent effects on them. Screening the plant materials which elicited statistically attractant effects on both the adult and juvenile snails under simulated natural condition (SNC) revealed that all seven plant products in plastic cylinders (trapping units) attracted more B. pfeifferi snails than the control traps. Lettuce was found to be the most potent attractant (P < 0.001) under SNC,

followed by pawpaw leaves (P < 0.001) > cocoyam leaves (P < 0.001) > cabbage (P < 0.001) > water melon (P < 0.001) > sweet potato (P < 0.001) > 3 day fermented cassava (P < 0.01). The implications of these findings for the development of slow - release molluscicides for the selective removal of schistosome host snails are discussed.