Behavioral fever response in Rhodnius prolixus (Reduviidae: Triatominae) to intracoelomic inoculation of Trypanosoma cruzi.

INTRODUCTION

Behavioral fever is a response to infections with microorganisms observed in some poikilothermic animals. Rhodnius prolixus is involved in the transmission of two parasites: Trypanosoma cruzi (pathogenic for humans and transmitted in feces) and Trypanosoma rangeli (non-pathogenic for humans, pathogenic for Rhodnius and transmitted by the bite of an infected individual). Only T. rangeli is found in the hemolymph of Rhodnius as it travels to the salivary glands.

METHODS

To study vector-parasite interactions, we evaluated possible behavioral fever responses of R. prolixus to intracoelomic inoculation with T. cruzi or T. rangeli. Temperature preferences of fifth-instar nymphs of R. prolixus were evaluated after inoculation with T. rangeli KP1(+), KP1(-), T. cruzi I, or the Trypanosome culture medium. Four different fixed temperatures (25, 30, 35, and 40°C) in two simultaneous experiments (enclosed and free-moving insects) were evaluated. Free-moving insects were marked daily according to their temperature preferences on each of the 15 days after inoculation. Numbers of insects in each temperature shelter and daily mortality were compared with those enclosed shelters of different temperatures.

RESULTS

Rhodnius prolixus inoculated with both strains of T. rangeli and with the trypanosome culture medium showed preferences for the lowest temperatures (25°C). However, R. prolixus inoculated with T. cruzi I showed significant preferences for temperatures around 35°C.

CONCLUSIONS

This is the first known investigation to demonstrate a behavioral fever response in R. prolixus injected intracoelomically with T. cruzi I.