Killets, Keswick Caroline (2021-11). Comparative Feeding and Defecation Behaviors of Triatomines and Their Relation to the Risk of Trypanosoma cruzi in the United States. Master's Thesis.
Thesis
Triatomines are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. They exhibit stercorarian transmission, in which T. cruzi is transmitted via fecal contamination to the host. Differential feeding and defecation behavior may contribute to the lower burden of human Chagas disease in the U.S. compared to Latin America, but behaviors of species in the U.S. have been infrequently studied. We hypothesized that U.S. triatomines less commonly defecate during or shortly after blood-feeding when compared to a South American triatomine species. We reared T. cruzi-infected (TcI and TcIV) and uninfected Triatoma gerstaeckeri and Triatoma sanguisuga (both of the southern U.S.) and Rhodnius prolixus--a South American triatomine sourced from a colony maintained by the U.S. Centers for Disease Control and Prevention. Single nymphs were allowed to interact with a restrained guinea pig for one-hour during which insect feeding and defecation events were measured. In 148 trials across all three species, 40.0% of insects fed at least once, of which 71.2% defecated during the observation period. Compared to R. prolixus, T. gerstaeckeri were more likely to feed and had more feeding events, and T. sanguisuga fed longer. The average interval between feeding to the first defecation was 4.5 min for R. prolixus, 9.8 min for T. gerstaeckeri and 20.7 min for T. sanguisuga, and there were observations of simultaneous feeding and defecation in all three species. The defecation index reported a similar pattern with R. prolixus having the highest infection capacity, followed by T. gerstaeckeri and then T. sanguisuga. Triatomines that were infected with T. cruzi DTU TcI were less likely to feed than uninfected controls, while those infected with TcIV had no significant differences. Finally, T. cruzi-infected insects had shorter post-feeding defecation intervals when considering multiple defecation events. These data suggest that while the feeding and defecation behaviors of T. gerstaeckeri and T. sanguisuga result in them being less efficient vectors compared to R. prolixus, they are still capable of stercorarian transmission. These observations suggest that other extrinsic and intrinsic factors contribute to the reduced autochthonous transmission of T. cruzi in the U.S. compared to elsewhere in the Americas.
