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

ABSTRACT The behavioural responses o f two schistosom e host snails (Bitlinus Iruncattts and Biomphalaria pfeifferi) to tw enty-six naturally occurring (crude and sem i-processed) products weic measured in diffusion olfactom eters. 15 out o f these 26 m aterials (i.e. 57% ) were found to act as statistically significant attractants for adult 13. pfeifferi w hile only 5 (19%) o f 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 m aterials com pared w ith their adult conspecifics; thus the juveniles o f B. truncatus responded to only 3 (i.e. 1 1.5%) o f the 26 natural products tested w hile those o f/i. pfeifferi responded to 34% o f the natural products. 13 out o f the 15 significant attractants for adult B. pfeifferi w ere found to be statistically significant arrestants w hile only 2 out o f the 5 significant attractants for adults o f B. truncatus elicited statistically significant arrestant responses. N one o f 26 test materials acted as statistically significant arrestant for juveniles o f B. truncatus. O f the 9 test m aterials w hich acted as significant attractants for juveniles o f B. pfeifferi 5 w ere found to aU as statistically significant arrestants. Preliminary investigations conducted under sim ulated natural conditions (SN C ) revealed that sugarcanc (Sacclianini officinarum) presented as chunks (whole) in bam boo cylinders (trapping units) attracted more snails (both Bulinus truncatus and Biomphalaria pfeifferi) than controls. This particular trapping unit was also found to be m ore effective than com parable units which used paw paw (Ccirica papaya), sw eet potato (lpomoea batatas) and cassava (Manihot esculenta). The efficacy o f the sugarcane-bam boo cylinder combination was again dem onstrated under field conditions in W eija lake w here in threeseparate cases a significantly higher num ber o f schistosom e host snails w ere caught in the test (raps com pared w ith controls. The im plications o f this study for the developm ent o f controlled released form ulations for the selective control o f schistosom e host snails are discussed.