BackgroundAlthough leishmaniases are regarded as serious public health issues in the State of Tocantins, as consequence of the impact of environmental changes, small advances in taxonomic and ecological studies of Phlebotominae fauna are taking place in this state. The present study aimed to improve the knowledge about the sand flies, as well as about the aspects of the bioecology of leishmaniases vectors from Porto Nacional, a city that was directly impacted by the construction of Luís Eduardo Magalhães Hydroelectric Plant (HEP – Lajeado).Methodology/Principal FindingsSand flies were collected monthly using CDC light traps and Shannon traps for a period of 40 consecutive months, at different monitoring stations, where 7162 specimens were collected and 48 species were detected. Among the species found, 22 are first records in the state and seven are considered important vectors of leishmaniases. Lutzomyia longipalpis, the vector of American Visceral Leishmaniasis (AVL) showed higher frequency in urban compared to rural areas, and Nyssomyia whitmani, the vector of American Cutaneous Leishmaniasis (ACL), predominated in rural areas. The frequency and habits of sand fly vectors are discussed considering environmental characteristics and climatic factors.Conclusions/SignificanceThe construction of dams requires a great amount of labor, therefore attracting people from elsewhere. Increased migration, without adequate structure, leads to bad living conditions in new and unplanned settlements. It also leads to deforestation associated with environmental impacts, which can facilitate the spread of leishmaniases.This study discusses the importance of Lu. longipalpis and Ny. whitmani on the transmission cycles of leishmaniases in Porto Nacional and the record of Bi. flaviscutellata in periurban area of the city.

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Leishmaniases are considered serious public health problems, and their geographical expansion has enabled their establishment in urban areas of medium and large cities in Brazil. Continuous processes of deforestation, construction of dams, and hydroelectric plants, among others, cause environmental impact and may favor the increase in the number of human cases of leishmaniases, as well as the establishment of epidemic outbreaks. This scenario reflects the reality of some regions of Brazil, such as Tocantins State, which in recent years has recorded high levels of American visceral leishmaniasis (AVL). This study is aimed to analyze environmental and epidemiological factors related with the spatial and temporal distribution of AVL and with the occurrence of Lutzomyia (Lutzomyia) longipalpis, the main vector of AVL, in the state of Tocantins. The results indicate that the vector is adapted to all environments, especially the ones under human influence, and that anthropogenic environmental impacts can support the development and adaptation of AVL in Brazil. Such information could be applied in control strategies aimed at decreasing AVL incidence.

SummaryChagas disease is estimated to affect 8 million people worldwide and is responsible for approximately 10,000 deaths in Latin America every year [1]. Control of the triatomine bugs that transmit the flagellated parasite Trypanosoma cruzi has been the most successful strategy to avoid disease spread. Genes containing small open reading frames (smORFs, < 100 amino acids) constitute a putative reservoir of new vector control targets, since hundreds of these genes are present in insect genomes [2]. Here, we show that the prototypic smORF-containing gene mille-pattes/polished-rice/tarsalless (mlpt/pri/tal) [3-6] is essential for postembryonic development of the kissing bug Rhodnius prolixus and for T. cruzi metacyclogenesis during the nymphal stages. Injection of double-stranded RNA against mlpt (Rp-dsmlpt) during the nymphal stages leads to a plethora of phenotypes, which impair postembryonic development. First, fourth or fifth stage nymphs injected with Rp-dsmlpt do not moult even in the presence of the ecdysone receptor (EcR) mRNA. Second, Rp-dsmlpt nymphs have defects in gut morphology, delayed haemoglobin digestion, and decreased defecation volume compared with those of the control nymphs. Third, Rp-mlpt knockdown inhibits T. cruzi differentiation to the trypomastigote infective stage (metacyclogenesis) inside the R. prolixus gut. Overall, our study is the first to provide evidence that a smORF-containing gene regulates vector physiology and parasitic cycle thus enabling the development of novel molecular strategies to eliminate Chagas disease transmission.