Density-dependent timing of defaecation by Rhodnius prolixus, and its implications for the transmission of Trypanosoma cruzi.

Transmission of Trypanosoma cruzi is crucially dependent on the timing of defaecation by their insect vectors. Experimental studies on Rhodnius prolixus nymphs revealed a negative correlation between blood meal weight and defaecation time. Bugs which fed to repletion defaecated on average 7 min after feeding, whereas bugs with interrupted feeds defaecated about 1 h later. As blood meal weight of triatomine bugs is density-dependent, these results suggest that the greatest risk of successful T. cruzi transmission would occur in recently colonized houses where the bug population is still increasing, or in houses recolonized after a vector control attempt.