Epidemiologia da leishmaniose americana da região do Parque Nacional dos Lençóis Maranhenses: enfoque na identificação das espécies de leishmânias e na capacidade vetorial dos flebotomíneos

Abstract

Leishmaniasis are a group of neglected infectious and parasitic diseases, with major repercussions at global and national level. In the State of Maranhao, both the American Cutaneous Leishmaniasis (LTA) and the American Visceral Leishmaniasis (LVA) are endemic and have great prominence at the national scene. Within the state territory, one of the leading regions is the Lençóis Maranhenses National Park - PNLM, whose surroundings have undergone environmental and ecological damage caused by man, resulting from direct and indirect tourism activities. As a result of this process every year are recorded cases, mostly LTA ones. Goals. Facing such reality, this study aimed: to define the epidemiological profile of the LTA between the years 2007 and 2013, taking into account demographic (age and gender), occupational and chronological features of the affected populations (reported cases); to demonstrate through a cartographic tool, a survey of the timeline distribution of cases of LTA; and an interactive map to determine the risk rate for acquisition of LT. It has been also proposed to study the transmission cycle of the disease, based on the identification of species of sandflies, their sources of blood and their Leishmania genus parasites, and additionally determining vector capacity of Lu. Whitmani toward Le. Braziliensis and Le. Amazonians. Methodology. The county of Barreirinhas was selected for this study because it is the main gateway to PNLM. In short, investigation of LTA cases was carried out in SINAN files, comprising all neighborhoods of the county (158), through the cycle 2007-2013, and sandflies collections were held in 62 of these communities. The species were identified taxonomically and females analyzed at the molecular level to research for natural infection by Leishmania, along with the animals that served as a food source. Results. 458 positive cases of LTA were reported between the years 2007 and 2013, predominantly in men from rural areas and farmers. The cases were concentrated in the south central area of the county, all year round. There was some geographic expansion with the emergence of new outbreaks, however, it was observed the persistence of the former areas of occurrence of the disease. As for the risk rates, villages Sítio Barra, Engenho and Manoelzinho were those who were positive for all variables. On the other side, the communities Quebra, Santa Rosa and Fumaça, presented less risk, since almost all the variables studied were negative for these locations. As for the sandflies, 9,853 specimens of 18 species have been collected, all present in extra-domicile (forest) and only 12 occurring in peri-domicile areas. The incidence was higher in areas surrounding dwellings (56.2%) than in extra-domicile environment (43.8%) and females predominated (51.4%) over males (48.6%). The dominant species were Lu. whitmani (53.83%), Lu. longipalpis (25.60%), Lu. Lenti (11.69%), Lu. evandroi (5.50%) and Lu. flaviscutellata (0.87%). Natural infections due to Le. infantum, were found in females captured in peri-domicile in five villages and extra-domicile in other two. The species Lu. longipalpis, vector of Le. Infantum, indicated a positivity rate of 3.7% for this species. While species not considered insect vector of this leishmania, such as Lu. Lenti and Lu. Whitmani, even so presented infection rates of 0.6% and 0.9%, respectively. Rates of natural infection due to Le. braziliensis, were detected in peri-domicile in two locations; while in Lu. Whitmani, considered the vector of this Leishmania species, rate of 0.3% was found. The rate of infection due to Le. amazonensis was 8% for Lu. Flaviscutelata, captured in peri-domicile in two villages and extra-domicile in just one. Lu. whitmani was able to get infected with Le. Braziliensis and Le. Amazonians. Concerning food source hosts, the following were identified: equines (9.0%), human (1.4%), canine (27.4%), rodent (3.3%), fowl (20.9%) and hogs (37.9%). Conclusion. All elements of the epidemiological chain of Leishmaniasis were present within the area of study, both in peri-domicile and extra-domicile areas, which explains the endemic state of the disease in the region.