Fatores entomológicos envolvidos na transmissão de malária em comunidades da área de abrangência da Hidrelétrica de Curuá-una, Santarém, Pará, Brasil

Abstract

An entomological survey was conducted in the area of influence of Hydroelectric Curuá-una, Pará State, to study the occurrence and behavior of species of Anopheles. We analyzed the records of the 9th Regional Health Centre (9 CRS / SESPA) and the obtained data on the incidence, distribution and behavior of species of epidemiological importance, and on the infectivity of Anopheles. The study was conducted from July 2008 to December 2009 at sites located upstream and downstream of Curuá-una dam. Captures were conducted in both adult (winged) and immature stages (larvae of 3rd and 4th instar). The adult specimens were collected with catcher Castro in indoor and outdoor environments in the period from 18h to 22h and 06h to 18h. After identification, specimens were evaluated to assess of natural infection rate with Plasmodium sp. by means of PCR. Considering the two study areas - upstream and downstream of the dam, the identification of specimens collected enabled the recording of 12 species of Anopheles. Of the total of 6715 specimens, 6534 were adults and 181 specimens consisted of immature forms. The species are distributed in three genera; Nyrssorhynchus, Anopheles and Stethomya. Anopheles albitarsis was the predominant species, that Anopheles darlingi was the second most frequent. In general, the Anopheles were found more frequently in peridomestic environment. Anopheles darlingi owned nocturnal activity concentrated between 19 and 21-20h-22h, and the same pattern observed in the downstream. Of the 317 samples (pools) analyzed, nine were positive for Plasmodium vivax, seven for A. darlingi, one for A. albitarsis and one for Anopheles nuneztovari. Based on the results it was concluded that the populations of A. darlingi predominate in animal sheds and biting activity continued during the night. Catches of 12 hours in the species was also recorded throughout the schedules. It has been found a very low frequency of larvae in breeding sites. The rates of anthropophilic and zoophilia found, show that A. darlingi shows marked anthropophily compared with A. nuneztovari showing marked zoophilia. The study of these factors enabled entomological consider the dynamics of malaria transmission in the area of influence of Hydroelectric Curuá-una.