Trypanosoma cruzi, Etiological Agent of Chagas Disease, Is Virulent to Its Triatomine Vector Rhodnius prolixus in a Temperature-Dependent Manner

Abstract

It is often assumed that parasites are not virulent to their vectors. Nevertheless, parasites commonly exploit their vectors (nutritionally for example) so these can be considered a form of host. Trypanosoma cruzi, a protozoan found in mammals and triatomine bugs in the Americas, is the etiological agent of Chagas disease that affects man and domestic animals. While it has long been considered avirulent to its vectors, a few reports have indicated that it can affect triatomine fecundity. We tested whether infection imposed a temperature-dependent cost on triatomine fitness. We held infected insects at four temperatures between 21 and 30°C and measured T. cruzi growth in vitro at the same temperatures in parallel. Trypanosoma cruzi infection caused a considerable delay in the time the insects took to moult (against a background effect of temperature accelerating moult irrespective of infection status). Trypanosoma cruzi also reduced the insects’ survival, but only at the intermediate temperatures of 24 and 27°C (against a background of increased mortality with increasing temperatures). Meanwhile, in vitro growth of T. cruzi increased with temperature. Our results demonstrate virulence of a protozoan agent of human disease to its insect vector under these conditions. It is of particular note that parasite-induced mortality was greatest over the range of temperatures normally preferred by these insects, probably implying adaptation of the parasite to perform well at these temperatures. Therefore we propose that triggering this delay in moulting is adaptive for the parasites, as it will delay the next bloodmeal taken by the bug, thus allowing the parasites time to develop and reach the insect rectum in order to make transmission to a new vertebrate host possible.

Screening of Fungi for Biological Control of a Triatomine Vector of Chagas Disease: Temperature and Trypanosome Infection as Factors

“…prolixus caused by T . cruzi infection at 24 and 27°C, reported recently [23] and observed again in the T . cruzi -parasitized insects here at the higher temperatures—i.e.…”

“…Parasites are passaged through triatomines and mice every six months to maintain the strain infectivity [23]. Briefly, nymphs are infected with culture epimastigotes through artificial feeding.…”

Triatomine bugs, their microbiota and Trypanosoma cruzi: asymmetric responses of bacteria to an infected blood meal

“…It is now known that T. cruzi reduces vector fitness [59, 60]. In situations where the host is unable to eliminate the parasite via direct immune responses, it may have to rely on its microbiota to fight against the parasite.…”

Projected expansion in climatic suitability for Trypanosoma cruzi, the etiological agent of Chagas Disease, and five widespread Triatoma species by 2070: the role of climate change on infectious diseases

“…Elevating temperature can directly increase the potential for vector-borne diseases and pathogens to increase in disease morbidity [62–64]. For instance, rises in temperature can increase the development time for Plasmodium, T. cruzi , and schistosome cercaria [63], [65–67]. Consequently, elevating temperature may affect the pathogen transmission potential and pathogen mortality might increase.…”

“…One group of authors examined the influence of temperature on the development of T. cruzi while in Rhodnius prolixus , which is a common South American vector [67]. The authors hypothesized that the temperature preference of R. prolixus also is an optimum temperature range of T. cruzi , which is 25.0-25.4°C [79].…”