Abstract
This study aimed to contribute to our knowledge of the parasite-vector interaction associated with Trypanosoma cruzi (Chagas, 1909) infection in Panstrongylus megistus (Burmeister, 1835), an important vector of Chagas' disease in Brazil. The prevalence and intensity of T. cruzi infection, the incidence of metacyclogenesis and the frequency of nuclear phenotypes in Malpighian tubules were investigated in nymphs of P. megistus, reared at 28 °C and subjected to heat shock (40 °C, 1 hour) two days after infection with T. cruzi II (Y strain). Following the 45-day post-infection period, the frequency of epimastigotes was much higher than that of trypomastigotes in both heat-shocked and non-shocked insects, and the prevalence of infection was not altered by heat shock. Fewer epimastigotes and trypomastigotes were found in the infected insects subjected to the heat shock, indicating that the multiplication and metacyclogenesis of the parasites were affected by the stress. In infected specimens heat shock promoted an increased frequency of cell nuclei with heterochromatin decondensation, a cell survival response to stress, and did not affect insect survival. The effects of infection and heat shock, especially on the multiplication and metacyclogenesis of T. cruzi, and the observed resistance to heat shock developed by P. megistus nymphs are suggestive that they should be considered when adequate conditions for rearing these infected insects in the laboratory are pursued.
Highlights
Trypanosoma cruzi (Chagas, 1909), the etiological agent of Chagas’ disease, is a flagellate protozoan with variable patterns of virulence, pathogenicity and infectivity in animals (Contreras et al, 1998)
We examined the prevalence and intensity of infection by T. cruzi and the level of metacyclogenesis 45 days post-infection in P. megistus reared at 28 °C and subjected to heat shock
The frequency of T. cruzi - 77.7% in non-shocked insects (n = 36) and 71.8% in shocked insects (n = 39) found 45 days after parasite ingestion did not significantly differ (p = 0.410), indicating that heat shock did not alter the prevalence of infection
Summary
Trypanosoma cruzi (Chagas, 1909), the etiological agent of Chagas’ disease, is a flagellate protozoan with variable patterns of virulence, pathogenicity and infectivity in animals (Contreras et al, 1998). In the case of T. cruzi, some vector species can potentially limit human and animal infection because they do not favour metacyclogenesis (Perlowagora-Szumlewicz and Moreira, 1994). The use of xenodiagnosis in the chronic phase of Chagas’ disease, either as a diagnostic aid or in conjunction with the administration of drugs against trypanosomes, has led to a search for hemipteran species that are highly susceptible to T. cruzi and could serve as experimental models (Alvarenga and Bronfen, 1984; Silva et al, 1994)
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