Rhodnius prolixus impairs Trypanosoma cruzi growth through cold-seeking behavioral thermoregulation.

Chagas disease, caused by the parasite Trypanosoma cruzi, is a major neglected tropical disease affecting 6-7 million people worldwide. Rhodnius prolixus, one of the most important vectors of Chagas disease in Latin America, is known to be highly sensitive to environmental temperature, which influences both its biology and parasite development. However, few studies have investigated how this vector behaviorally modulates the effects of temperature by shifting their thermopreference, particularly in response to infection. We investigated how T. cruzi infection of R. prolixus fourth-instar nymphs influences thermopreference along a temperature gradient, while examining differences across times of day and time since blood feeding. Additionally, parasite load and infection maintenance were compared between free-moving nymphs and nymphs kept at a constant 26°C. Infected nymphs exhibited a preference for temperatures approximately 1°C cooler than uninfected controls. This cold-seeking behavior emerged around 15 days post-infection and persisted until shortly after molting. Importantly, infected insects allowed to thermoregulate showed significantly lower intestinal parasite loads and a higher rate of infection clearance compared to those kept at a constant 26°C. A diurnal cycle in temperature preference was also observed, with higher preferred temperatures shortly after the beginning of the photophase, followed by a gradual decline over the day and night. These results suggest the existence of an infection-induced behavioral anapyrexia response in R. prolixus that limits T. cruzi development. This potential form of adaptive thermoregulation has important implications for the ecology of Chagas disease transmission and the development of behaviorally informed vector control strategies.