Background Chagas disease is a parasitic infection with high re-emergence rates in some Amazon regions. The main vectors of Trypanosoma cruzi are haematophagous insects, the triatomines. Only a few reports are available about the occurrence of these wild vectors and their contact with the inhabitants of the riverside regions of the Amazon. This study describes the unusual behaviour of the triatomines that have invaded the homes of the residents of Abaetetuba, the city that has the second highest number of cases of Chagas disease. Methods Two cross-sectional studies were conducted using sero-epidemiological surveys of the inhabitants of Abaetetuba with registered triatomine home invasions. The frequencies of the variables of interest were analysed using Epi Info version 7.2. Results In 2014 and 2017, 145 persons registered home invasions of triatomines in their domiciles and 16.55% reported having been bitten by insects. The environmental features described indicated potential conditions for the persistence of the parasite's life cycle. Of the enrolled inhabitants, 0.47% were positive for immunoglobulin G anti-T. cruzi antibodies. Conclusions Home invasions of triatomines were confirmed in two periods, with a description of unusual behaviour for the genus Rhodnius. The use of serological surveillance in human populations at risk of this occurrence may constitute a new tool for the early detection of silent infections.

No abstract

Chagas disease is a parasitic infection with a large reemergent rates in some Amazon regions with usual features of outbreaks of the acute disease mainly by oral transmission. The main vectors of Trypanosoma cruzi are hematophagous insects, the triatomines. Some of them can establish themselves in human dwellings and their annexes but others are mostly wild. In the state of Pará, few records have been made about the occurrence of those wild vectors in fortuitous contact with inhabitants in riverside regions in the Amazon. These vector behaviours have been studied by our group since 2006, trying to explain their role in transmission of the silent disease or asymptomatic infection. The objective of this study is to describe the epidemiological profile of populations exposed to random triatomine home invasion in riverside areas with this registered occurrence. This is a cross-sectional study developed in Abaetetuba city, in the state of Pará, where we conducted a seroepidemiologic survey in inhabitants that registered triatomine home invasion. The results demonstrated that triatomine invasions occur especially in the in-home environment and in the rural zone. The genus Rhodnius was the most found in residences of the municipalities. Direct contact through the vector was reported by 15.55% of the total participants, and an unusual vector behaviour were observed during the day. Despite this small casuistic, 0.47% of the enrolled inhabitants had positive serology IgG anti- T. cruzi antibodies. We confirm one occurrence of asymptomatic infection in a child and, also, favourable links to the Chagas disease transmission chain. Faced with the scarcity of information on triatomine aggression in the Amazon, the authors recommended an entomological study of greater scope in those areas. The record of unusual vector behaviour and the serological surveillance of human populations under this risk may constitute a new tool for the early detection of silent infections and reinforce the knowledges about the behaviour of invading insects. At the same time, health education can assist in strategies for the prevention of Chagas' disease.