Identification and field evaluation of bioactive natural products for use in schistosome host snail traps

Abstract

The behavioural responses of two schistosome host snails (Bitlinus Iruncattts and Biomphalaria pfeifferi) to twenty-six naturally occurring (crude and semi-processed) products weic measured in diffusion olfactometers. 15 out of these 26 materials (i.e. 57%) were found to act as statistically significant attractants for adult 13. pfeifferi while only 5 (19%) of the lest materials clicited statistically significant responses from the adults o f B. truncatus. The juveniles oil the whole were less responsive to the lest materials compared with their adult conspecifics; thus the juveniles o f B. truncatus responded to only 3 (i.e. 1 1.5%) of the 26 natural products tested while those o f /i. pfeifferi responded to 34% of the natural products. 13 out of the 15 significant attractants for adult B. pfeifferi were found to be statistically significant arrestants while only 2 out of the 5 significant attractants for adults o f B. truncatus elicited statistically significant arrestant responses. None of 26 test materials acted as statistically significant arrestant for juveniles o f B. truncatus. of the 9 test materials which acted as significant attractants for juveniles o f B. pfeifferi 5 were found to aU as statistically significant arrestants. Preliminary investigations conducted under simulated natural conditions (SNC) revealed that sugarcanc (Sacclianini officinarum) presented as chunks (whole) in bamboo cylinders (trapping units) attracted more snails (both Bulinus truncatus and Biomphalaria pfeifferi) than controls. This particular trapping unit was also found to be more effective than comparable units which used pawpaw (Ccirica papaya), sweet potato (lpomoea batatas) and cassava (Manihot esculenta). The efficacy of the sugarcane-bamboo cylinder combination was again demonstrated under field conditions in Weija lake where in three separate cases a significantly higher number of schistosome host snails were caught in the test (raps compared w ith controls. The implications of this study for the development of controlled released formulations for the selective control of schistosome host snails are discussed