Strong Host-Feeding Preferences of the Vector Triatoma infestans Modified by Vector Density: Implications for the Epidemiology of Chagas Disease

Abstract

BackgroundUnderstanding the factors that affect the host-feeding preferences of triatomine bugs is crucial for estimating transmission risks and predicting the effects of control tactics targeting domestic animals. We tested whether Triatoma infestans bugs prefer to feed on dogs vs. chickens and on dogs vs. cats and whether vector density modified host choices and other vital rates under natural conditions.MethodologyTwo host choice experiments were conducted in small caged huts with two rooms between which bugs could move freely. Matched pairs of dog–chicken (six) and dog–cat (three) were assigned randomly to two levels of vector abundance and exposed to starved bugs during three nights. Bloodmeals from 1,160 bugs were tested by a direct enzyme-linked immunosorbent assay.Principal FindingsConditional logistic regression showed that dogs were highly preferred over chickens or cats and that vector density modified host-feeding choices. The relative risk of a bug being blood-engorged increased significantly when it fed only on dog rather than chicken or cat. Bugs achieved higher post-exposure weight at higher vector densities and successive occasions, more so if they fed on a dog rather than on a cat.ConclusionsOur findings strongly refute the hypothesis that T. infestans prefers to blood-feed on chickens rather than dogs. An increase in dog or cat availability or accessibility will increase the rate of bug feeding on them and exert strong non-linear effects on R 0. When combined with between-dog heterogeneities in exposure, infection, and infectiousness, the strong bug preference for dogs can be exploited to target dogs in general, and even the specific individuals that account for most of the risk, with topical lotions or insecticide-impregnated collars to turn them into baited lethal traps or use them as transmission or infestation sentinels based on their immune response to Trypanosoma cruzi or bug salivary antigens.

High Frequency of Human Blood in Triatoma dimidiata Captured Inside Dwellings in a Rural Community in the Yucatan Peninsula, Mexico, but Low Antibody Seroprevalence and Electrocardiographic Findings Compatible with Chagas Disease in Humans

“…Notably, we observed that, when mouse, dog, and chicken blood was identified in T. dimidiata, human blood was also identified, suggesting that the vector is able to disperse between peridomicile and domicile sites to search for better host availability and accessibility as previously reported. 21 The above data, in addition to the infection index of triatomines trapped inside houses of 38%, may suggest that high risk of T. cruzi infection to humans could exist in this community, but seroprevalence against T. cruzi in the population revealed only 2.3% (3/128). This seroprevalence is low compared with other endemic regions, such as the states of Chiapas and Oaxaca in Mexico (their seroprevalence is above 10%), 22 and exceptionally high 67% and 32% in some communities of Oaxaca and Chiapas, respectively.…”

Vector host-feeding preferences drive transmission of multi-host pathogens: West Nile virus as a model system

“…Culex nigripalpus, a major vector for Saint Louis encephalitis in the southern United States, preferred chickens to bobwhite quail in a host-choice experiment in Florida, USA [64]. Host preferences are not exclusive to mosquitoes: Triatoma bugs that transmit Chagas' disease demonstrated strong feeding preferences for dogs over both chickens and cats in a recent study [65]. At least one species of tsetse fly (Glossina morsitans morsitans), vector of human (sleeping sickness) and animal trypanosomiasis in Africa, show feeding preferences towards buffalo and oxen but avoid other hosts such as waterbuck (reviewed in [66]).…”

Vector Blood Meals Are an Early Indicator of the Effectiveness of the Ecohealth Approach in Halting Chagas Transmission in Guatemala

“…Various factors such as season, developmental stage, and vector density, may affect the feeding patterns of vectors, thus it would be important to monitor blood sources at different times of the year if blood sources are to be used to evaluate control programs. 32,33,35,36 Although there was a significant decrease in vectors containing dog blood meals, dogs remain an important reservoir animal in Guatemala, as they are elsewhere [37][38][39] ; the majority of the blood meals found before the interventions were dog, and even after the interventions nearly 30% of vectors had fed on dog. Usually houses have many dogs and there is no breeding control.…”