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

Abstract

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 fi fth-instar nymphs of R. prolixus were evaluated after inoculation with T. rangeli KP1(+), KP1(-), T. cruzi I, or the Trypanosome culture medium. Four different fi xed 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 signifi cant preferences for temperatures around 35°C. Conclusions: This is the fi rst known investigation to demonstrate a behavioral fever response in R. prolixus injected intracoelomically with T. cruzi I.

Activity of the prophenoloxidase system and survival of triatomines infected with different Trypanosoma cruzi strains under different temperatures: understanding Chagas disease in the face of climate change

“…For instance, Botto-Mahan [61] found that T. cruzi infection delays the development and reduces survival rates in the triatomine Mepraia spinolai . Studies more closely related to our work found that T. cruzi reduced the survival of the triatomine Rhodnius prolixus , but only at 20 °C and 30 °C [31, 34]. In our case, the insects were more affected by the Chilpancingo strain than by the Morelos strain.…”

“…It is worth noting, however, that despite the strong effect of higher temperatures on reduced survival, this does not mean that the triatomine bugs do not rely on a fever response to deal with pathogens. Actually, other studies have found that triatomines show fever responses when sick [34]. It would be interesting to see whether M. pallidipennis bugs increase their fitness when allowed to choose ambient temperatures while facing different T. cruzi isolates.…”

“…Such an increase would result in a higher risk of T. cruzi transmission [28–30], but a balance could be established due to a possible decrease in triatomine survival [26, 31–33]. It is not clear whether this decrease in survival rate is due to an interaction with the parasite, since higher temperatures are expected to favor a more robust prophenoloxidase activity (a proxy of the insect’s immune response) in the vector [28, 34–36].…”

An Update on the Knowledge of Parasite–Vector Interactions of Chagas Disease

“…As in other animals, the immune system of triatomines consists of cellular and humoral components that respond to pathogens and parasites, 52–54 also including behavioural fever responses. 55 Cellular components have only been found in the hemolymph and not in any section of the intestine. If viruses, bacteria, fungi and parasites gain access to the intestine, the humoral immunity is activated via the immune deficiency (IMD), Toll and JAK-STAT pathways 52 , 56 that induce the production of different antimicrobial peptides (eg, lysozymes, defensins, prolixin, prophenoloxidase cascade), unidentified bacteriolytic compounds and antimicrobial molecules (eg, nitric oxide).…”

Coinfection by Trypanosoma cruzi and a fungal pathogen increases survival of Chagasic bugs: advice against a fungal control strategy

“…Peterson et al ., 2016; Cordero-Montoya et al ., 2019; reviewed by de Oliveira et al ., 2018). This cost could lead the insect to enhance its immune response (de Fuentes-Vicente et al ., 2016), removing up to 80% of the parasites within hours after ingesting infected blood (Elliot et al ., 2015; Hinestroza et al ., 2016).…”