Effect of Bacillus thuringiensis var. israelensis Endotoxin on the Intermediate Snail Host of Schistosoma japonicum

Bacillus thuringiensis demonstrates a very wide spectrum of biological activities. It is gaining widespread acceptance in the control of pests and vectors of diseases. Few reports have described the responses of the intermediate host of Schistosomes to B. thuringiensis toxins. This preliminary study showed the effect of Bacillus thuringiensis israelensis endotoxin on the intermediate host of Schistosoma japonicum under laboratory conditions. The alkali soluble endotoxin protein of two B. thuringiensis israelensis strains; (977) and (NRRL HD-522) were bioassayed for its toxicity against non-infected Chinese Oncomelania snails then analyzed using SDS-PAGE. The toxin concentration of 20 ng mL-1 from both strains resulted in 0% mortality after 48 h, but the concentration of 0.9 μg mL-1 resulted in 70% mortality after 24 h. Bioassays indicated that non-infected Chinese Oncomelania snails are susceptible for the soluble protein of the test strains at high concentrations only. SDS-PAGE polypeptide pattern of the soluble proteins investigated against snails, with a predominant protein bands at about 66, 53, 35 and 28 kDa. The soluble proteins of the test strains have molluscicidal activity towards non-infected Chinese Oncomelania snails at high concentrations only.