Density-dependent timing of defaecation by Triatoma infestans.

Defaecation timing of the Triatominae vectors of Trypanosoma cruzi directly affects the transmission probability of Chagas disease to mammal hosts. Experimental studies with fifth instar nymphs of Triatoma infestans showed that defaecation time was negatively affected by blood meal size and positively affected by starvation period and bug initial weight. Since blood meal size and starvation period are both density-dependent, low density domestic populations of T. infestans would represent a higher transmission risk than high density populations. As low density populations could occur in recently reinfested houses after control using insecticide, vigilance activities should be reinforced to protect the human population at the highest risk of disease transmission.