Effect of azadirachtin on the development of Trypanosoma cruzi in different species of triatomine insect vectors: long-term and comparative studies.

Studies were carried out on the effects of azadirachtin on the course of Trypanosoma cruzi infection in the gut of different triatomine vector species. In Rhodinus prolixus the development of T. cruzi clone Dm28c decreased in a dose-dependent manner, and the ED50 of this inhibitory effect was 0.25 microgram azadirachtin/ml bloodmeal. Using this insect, we conducted a long-term experiment which showed that azadirachtin (1.0 microgram/ml bloodmeal) completely blocks the development of T. cruzi even 120 days after treatment with the drug, and after four infectant meals. Similarly, the elimination of T. cruzi in feces and urine was also completely blocked over a period of 50 days after infection in insects treated with azadirachtin. Fifth-instar larvae of R. prolixus, Triatoma infestans, and Dipetalogaster maximus, infected with different clone/strains of T. cruzi, displayed drastic inhibition of trypanosome development when treated with azadirachtin. The discussion of these results focuses on the possibility that azadirachtin may act directly on gut physiology and/or indirectly through the neurosecretory system.