Avaliação da susceptibilidade de Rhodnius prolixus e Triatoma maculata à infecção pelo Trypanosoma cruzi após submissão ao xenodiagnóstico de pacientes com doenças de Chagas

Abstract

INTRODUCTION: American trypanosomiasis, better known as Chagas disease, in honor of its discoverer, physician Carlos Chagas, is among the five most important endemic diseases in Latin America. This disease is caused by the flagellate protozoan, Trypanosoma cruzi, and is traditionally transmitted to humans through the contaminated feces of vector insects belonging to the subfamily Triatominae, known as barbeiros. Xenodiagnosis is a method used as a parasitological examination to complement the diagnosis of this disease. The procedure uses triatomines as a biological culture medium for the detection of T. cruzi infection. Studies suggest that xenopositivity may be associated with greater or lesser susceptibility of the triatomine species. OBJECTIVE: To evaluate the susceptibility of two species of triatomines (Rhodnius prolixus and Triatoma maculata) to T. cruzi infection used during the xenodiagnosis of patients with Chagas' disease. METHODS: Two groups of 20 nymphs of the 3rd stage of the species, created in the laboratory, used in the xenodiagnosis of 16 carriers of Chagas' disease were followed up. The nymphs were weighed before and after the blood meal and the feces were observed on slides, through the fresh examination, in readings, performed at intervals of 15, 60, 90, 180 days after the xenodiagnosis. RESULTS: It was observed that Rh. prolixus ingested a greater amount of blood (mean of 0.199g) than T. maculata (0.143), with a difference of 0.056. The average Rh weight. prolixus before the meal was 0.033g and after it was 0.232g while T. maculata before it was 0.068g and after it was 0.211g. There was no positivity for T. cruzi infection in the two species after the analysis of 496 slides in the four established time intervals. CONCLUSION: The presence of infection by T. cruzi in the species observed during 180 days after xenodiagnosis was not observed using the direct fresh examination method. It is observed, however, that Rh. prolixus ingested a greater amount of blood than T. maculata, which indicates the need for investigation of infection by more sensitive methodologies before inferring the absence of parasitemia in carriers or that the species is not susceptible to infection by Trypanosoma cruzi. Keywords: Chagas disease, Xenodiagnosis, Susceptibility.