Elucidating the Mechanism of Acquisition by Triatomine Insects: Evidence from a Large Field Survey of .

Blood-sucking triatomine bugs transmit the protozoan parasite , the etiologic agent of Chagas disease. We measured the prevalence of infection in 58,519 captured in residences in and near Arequipa, Peru. Among bugs from infected colonies, prevalence increased with stage from 12% in second instars to 36% in adults. Regression models demonstrated that the probability of parasite acquisition was roughly the same for each developmental stage. Prevalence increased by 5.9% with each additional stage. We postulate that the probability of acquiring the parasite may be related to the number of feeding events. Transmission of the parasite does not appear to be correlated with the amount of blood ingested during feeding. Similarly, other hypothesized transmission routes such as coprophagy fail to explain the observed pattern of prevalence. Our results could have implications for the feasibility of late-acting control strategies that preferentially kill older insects.