Malaria vectors in two indigenous reserves of the Brazilian Amazon

Abstract

OBJECTIVE: To describe the composition, ecological and behavioral characteristics and infectivity of Anopheles species in indigenous reserves of the Amazon region. METHODS: The study was performed in villages of the Nhamundá-Mapuera and Cuminapanema indigenous reserves, in the state of Pará, Northern Brazil, in 2002. A total of three two-week collections were conducted in each reserve, with the capture of adult and immature forms. Adult Anopheles specimens were captured using a Castro sucking tube with human landing trap in indoor and outdoor environments, from 6.00 pm to 9.00 pm and from 6.00 pm to 6.00 am, and subsequently assessed to verify parity and infectivity by plasmodiums using dissection and ELISA. Water collections near the villages were surveyed using 500 ml ladles, with 20 ladlefuls for each 10 m, covering the maximum extent of 200 m of perimeter around the breeding spot. RESULTS: Adding up the collections from both reserves, a total of 8,668 females were captured. Anopheles darlingi was the most frequent species, with higher frequency around the homes. In the Mapuera reserve, blood feeding activity was concentrated between 8.00 pm and 12.00 am, while, in Cuminapanema, it remained high until 12.00 am, decreasing after this time and increasing again early in the morning. Of all the 6,350 An. darlingi females analyzed, 18 were infected with Plasmodium vivax VK247, VK210, P. falciparum and P. malariae. In addition, other 1,450 females of other species were analyzed, but none was found infected. An. nuneztovari and Chagasia bonnae were the most frequent species in the breeding spots of the Mapuera and Cuminapanema villages, respectively. Immature An. darlingi forms were not located in Mapuera and were captured in only one of the collections of the Cuminapanema reserve. CONCLUSIONS: An. darlingi populations in the two reserves showed exophilic behavior and intense nocturnal activity. The occurrence of immature forms was little frequent and larval density was low. Vector behavioral characteristics were not favorable for the usual vector control activities.