This study was directed towards the use of non-harmful, non-pathogenic bacteria, Bacillus thuringiensis (B.T.) as a nematicide against Trichostrongylus colubriformis in rabbits. Eggs and larvae of adult nematode worms, T. colubriformis were obtained and exposed to six dilutions of B.T. Kurstaki 0.3, 0.6,1,1.5,2 and 2.5 mg and toxin. The biologically treated eggs and larvae were incubated at 28 degrees C. and examined for development, activity and motility. The ovicidal and larvicidal activity of B.T. Kurstaki and its toxin were recorded. Also anthelmintic activity of B.T. Kurstaki against T. colubriformis infection in rabbits were evaluated by SC injection of infected rabbits with a dose of 5mg/kg body weight. Both treated infected rabbits and control ones were sacrificed after 2 weeks post treatment and the intestine was prepared for worm detection. The data were subjected to statistical analysis based on the work of Polo- Pc (Robertson et. al. 1980) to determine LD50 values. The ovicidal and larvicidal activities were higher with prolonged exposure of parasitic eggs and larvae to bacteria and its toxins. The ovicidal activity of bacteria and toxin were increased to be 93.71% and 93.66% respectively at 2.5 mg concentration. The larvicidal effects of bacteria reached to 100% and 98% for bacteria and toxin respectively at 2mg. Also the anthelmintic activity of B.T. kurstaki against T. colubriformis in rabbits showed a daily gradual decrease in number of eggs/gm. Feces and disappearances of eggs after 10 days post treatment. Also the intestine of sacrificed infected rabbits were free from adult nematode. The study reaveled the successful biological treatment of infested rabbits with T.colubriformis by non- harmful bacteria, B.T. kurstaki.

This work was supported by the National Research Center, Egypt.