Effects of azadirachtin on Rhodnius prolixus: immunity and Trypanosoma interaction

The effects of azadirachtin, a tetranortriterpenoid from the neem tree Azadirachta indica J., on both immunity and Trypanosoma cruzi interaction within Rhodnius prolixus and other triatomines, were presented. Given through a blood meal, azadirachtin affected the immune reactivity as shown by a significant reduction in numbers of hemocytes and consequently nodule formation following challenge with Enterobacter cloacae beta 12, reduction in ability to produce antibacterial activities in the hemolymph when injected with bacteria, and decreased ability to destroy the infection caused by inoculation of E. cloacae cells. A single dose of azadirachtin was able to block the development of T. cruzi in R. prolixus if given through the meal at different intervals, together with, before or after parasite infection. Similarly, these results were observed with different triatomine species and different strains of T. cruzi. Azadirachtin induced a permanent resistance of the vector against reinfection with T. cruzi. The significance of these data is discussed in relation to the general mode of azadirachtin action in insects.