Triatomine host preference in an experimental cafeteria: the impact of Trypanosoma cruzi infections

Abstract

BackgroundHematophagous triatomine vectors of the Chagas disease parasite, Trypanosoma cruzi, have a wide bloodmeal host breadth yet mammals are the primary competent reservoirs for T. cruzi. Accordingly, the transmission of T. cruzi is dependent on triatomines encountering mammalian hosts. We hypothesized T. cruzi-infected triatomines exhibit a preference for mammalian versus non-mammalian hosts, as compared to uninfected triatomines. Methodology/Principal FindingsWe used a dual-choice olfactometer to present individual T. cruzi-infected and uninfected Triatoma gerstaeckeri- an important North American triatomine species- to pairwise combinations of no host, dog, human, or chicken. We found that uninfected T. gerstaeckeri preferred dogs over chickens and humans, but T. cruzi-infected T. gerstaeckeri had no host preference. Additionally, T. cruzi-infected T. gerstaeckeri took less time to begin advancing towards hosts (average of 522 s {+/-} 577 s vs 801 s {+/-} 704 s) and spent more time on both sides of the olfactometer compared to uninfected insects As a comparative group,we tested Rhodnius prolixus- a potent South American vector- and found no statistical preference among hosts, yet they advanced towards hosts more often (63.2% vs 47.1%) and faster compared to T. gerstaeckeri. Conclusions/SignificanceThe increased locomotion of R. prolixus and T. cruzi-infected T. gerstaeckeri toward hosts may promote increased transmission of T. cruzi. Dogs are a preferred host for T. gerstaeckeri and may be considered in future host-targeted interventions for triatomine control. Author SummaryVectors are often generalists or opportunists with a wide range of available hosts, yet the parasites they transmit may have a narrower host range. It is in the parasites best interest for the vectors they infect to interact with competent hosts, thereby introducing the setting for parasite manipulation of vectors. We aimed to understand the foraging behaviors of vectors and how those behaviors may be different when the vector is infected with a parasite. We studied the triatomine ( kissing bug) insect vectors of the Chagas disease parasite, Trypanosoma cruzi, using one of North Americas most important vector species in comparison to a potent South American vector species. We tested if parasite-infected triatomines exhibited a preference toward vertebrate hosts that are also competent reservoirs for the T. cruzi (i.e., mammals). We used an experimental cafeteria, in which individual vectors were introduced to a dual-choice olfactometer and allowed to walk toward hosts including restrained humans, dogs, or chickens. We found differences in apparent host preference between species of vectors and between infected vs. uninfected vectors. Uninfected vectors displayed a host preference toward dogs, yet this preference was not significant among infected vectors. Uninfected vectors had higher frequency of locomotion in the arena, suggesting the opportunity for more vector-host contact.