Abstract INTRODUCTION Triatomine bugs are hematophagous insects that are extremely important in public health because they are natural vectors of Trypanosoma cruzi, the causative agent of Chagas disease. In this study, we aimed to assess the occurrence of triatomine species and the natural T. cruzi infection in the Guaribas Valley territory, an endemic region for Chagas disease in northeastern Brazil. METHODS Insects were actively captured from July 2017 to October 2019 in the intra- and peridomiciles of 16 municipalities of the Guaribas Valley territory, in the southeast area of Piauí state. Triatomine species were identified following a taxonomic key, and natural infection was investigated through insects’ fresh feces exams. RESULTS A total of 430 triatomines were collected, including 211 nymphs and 219 adults. Of all collected specimens, 39 (9.1%) were from the intradomiciles and 391 (90.9%) from peridomiciles. Nine species, including two subspecies, could be identified: Triatoma brasiliensis brasiliensis, T. brasiliensis macromelasoma, T. pseudomaculata, T. sordida, T. juazeirensis, T. melanocephala, Panstrongylus lutzi, Rhodnius domesticus, R. nasutus, and R. robustus. T. brasiliensis were the most frequently collected bugs, representing 72% of all the identified insects. None of the examined invertebrates presented flagellate forms of T. cruzi. CONCLUSIONS: This is the first report of T. b. macromelasoma and T. juazeirensis in the Guaribas Valley territory. The persistence of triatomine species in the domiciles in an endemic area for Chagas disease emphasizes the relevance of entomological surveillance and vector control measures in the studied area.

Resumo: O período de seca pronunciado marca a região semiárida brasileira. Para superação dessa condição inúmeros reservatórios de pequeno porte são construídos, acumulando múltiplos usos e causando alterações importantes na paisagem e na biota local. Considerando as poucas informações sobre a malacofauna de reservatórios, principalmente na região nordeste do país, este trabalho apresenta o inventário das espécies de moluscos provenientes de três importantes reservatórios localizados no município de São Julião, estado do Piauí. As coletas foram realizadas mensalmente entre os meses de maio/2017 e abril/2018. Foi amostrado um total de 11.149 moluscos, correspondentes as espécies Melanoides tuberculata (Müller, 1774) (n=9,724), Biomphalaria straminea (Dunker, 1848) (n=1,361) e Pomacea lineata (Spix, 1827) (n=64). A riqueza de moluscos amostrados nos três reservatórios foi baixa, não diferindo daquelas descritas em estudos realizados em outras regiões do Nordeste do Brasil. Houve diferença significativa na abundância de M. tuberculata e B. straminea entre os reservatórios estudados os quais não são conectados e encontram-se instalados em áreas urbana e rurais, com condições ambientais distintas. A relação entre a população humana da região e os reservatórios, juntamente com a falta de saneamento representam riscos à propagação de doenças transmitidas pela água e desequilíbrio ambiental pela introdução de espécies exóticas.

Abstract: The pronounced dry season determines the characteristics of the semiarid region of Brazil. Numerous small reservoirs are built to overcome this condition, accumulating multiple uses and causing important changes in the landscape and the local biota. Considering the limited amount of information about the malacofauna of reservoirs, mainly in the Northeast region of the country, this inventory provides a list of mollusks from three important reservoirs located in the city of São Julião, state of Piauí. The collections were carried out monthly between May/2017 and April/2018, sampling a total of 11,149 mollusks, corresponding to the species Melanoides tuberculata (Müller, 1774) (n = 9,724), Biomphalaria straminea (Dunker, 1848) (n = 1,361) and Pomacea lineata (Spix, 1827) (n = 64). The richness of mollusks from the three reservoirs was low, similar to those described in studies conducted in other regions of Northeast Brazil. There was a significant difference in the abundance of M. tuberculata and B. straminea among the studied reservoirs. These environments are not connected and are installed in urban and rural areas, presenting different ecological conditions. The relationship between the human population and the reservoirs, associated with the lack of sanitation, increases the risks of spreading waterborne diseases besides the development of environmental imbalance by the introduction of exotic species.