Human intervention in the Brazilian Amazon region promotes contacts between humans and vectors that may favor the propagation of anopheline mosquitoes and the spread of malaria in the absence of planning and infrastructure to control this disease. Vector ecology studies were carried out to determine the risk areas. These data should help in designing appropriate malaria control measures. Data from 14 different regions are reported. Vectors are able to adapt to different environments, which made it necessary to study each area. The parameters studied were Anopheles breeding sites, species distribution, incidence, feeding preferences, hours of maximum activity of adult mosquitoes, seasonality, resting places, and the presence of Plasmodium. Species complexes were also studied. Anopheles darlingi may be responsible for maintaining malaria in human populations in this region. A reduction in the population density of A. darlingi in a particular geographic area can sometimes cause the disappearance of malaria. This species feeds at night but has a peak of activity at the beginning of the evening and another at dawn. Other species are mainly crepuscular and all anophelines demonstrated pronounced exophilia. The timing of feeding activities was found to vary in areas altered by human intervention and also depended on the time of the year and climatic conditions. The larvae were more abundant in the rivers with a less acidic pH and rural areas showed the highest larval index.

SUMMARYVarious species of Anopheles (Nyssorhynchus) were studied in the Amazon with the objective of determining their importance as malaria vectors. Of the 33 known Anopheles species occurring in the Amazon, only 9 were found to be infected with Plasmodium. The different species of this subgenus varied both in diversity and density in the collection areas. The populations showed a tendency towards lower density and diversity in virgin forest than in areas modified by human intervention.The principal vector, An. darlingi, is anthropophilic with a continuous activity cycle lasting the entire night but peaking at sunset and sunrise. These species (Nyssorhynchus) are peridomiciliary, entering houses to feed on blood and immediately leaving to settle on nearby vegetation.Anopheles nuneztovari proved to be zoophilic, crepuscular and peridomiciliary. These habits may change depending on a series of external factors, especially those related to human activity.There is a possibility that sibling species exist in the study area and they are being studied with reference to An. darlingi, An. albitarsis and An. nuneztovari. The present results do not suggest the existence of subpopulations of An. darlingi in the Brazilian Amazon.

In 1998, the FMT/IMT-AM foundation implemented the surveillance system to diagnose acute undifferentiated febrile syndromes, with the objective of active and passive surveillance in Brazilian western Amazonian rainforest to identify and diagnose the etiologic agents of acute fever. The diagnoses were performed using serological tests to detect IgM antibodies by ELISA (Enzyme-linked-immunosorbent assay) CDC/OPAS or using commercial kits. A total of 8,557 serum samples obtained from patients with clinical suspicion of dengue virus were analyzed. ELISA positive reaction to dengue virus was presented by 40% of the serum samples and 26% of the serum samples had positive ELISA reactions to other exanthematous viral diseases, such as rubella, measles, parvovirus, Oropouche virus and Mayaro virus.

Um inquérito entomològico foi realizado na área de influência da Hidrelétrica de Balbina, situada a 146 km de Manaus, Amazonas, para avaliar os possíveis efeitos sobre as populações de Anophelese de outros culicídeos. Cinco anos após a formação do lago, An. darlingi, An. nuneztovarie An. triannulatusforam as espécies encontradas com maior freqüência nas coletas realizadas em 1. Rodovia BR-174, 2. Acceso á Usina Hidrelétrica de Balbina e 3. Área Uatumã-Morena. Para cada espécie os índices mosquito/homem/hora foram respectivamente: Area 1 - 0,57; 12,85; 0,43. Área 2 - 0; 3,75; 0,18 e Área 3 - 0; 26,38; 0,34. Representantes das duas primeiras espécies se mostraram positivas para Plasmodiumcom testes imunoenzimáticos. A prevalência de mosquitos positivos foi 1:35 para An. darlingie apenas 1:548 para An. nuneztovari.A densidade dos outros culicídeos foi baixa (Área 1 - 3,23 m/h/h; Área 2 - 4,5 m/h/h; Área 3 - 7,40 m/h/h) embora a diversidade foi comparável ( 32 espécies diferentes) com as encontradas em outras hidrelétricas construídas em rios de águas brancas ou claras da Amazônia. Nas águas pretas da Balbina, uma proliferação inicial de macrófitas foi seguida pela redução destas possivelmente pela falta de nutrientes na água. A diminuição no crescimento de macrófitas deve estar relacionada com a escassez de Mansoniasp. na área.

The residual potential of an aqueous solution of Deltamethrin (FW 25 mg i.a./m) was evaluated on raffia curtains. These are sheets of synthetic material used in the construction of huts to house miners. Experiments were conducted during 420 days and the curtains were always rolled up in the daytime and unrolled in late afternoon. Data analyzed by logarithmic regression indicated that raffia treated with Deltamethrin had higher mortality indices than that covered with DDT. The residual capacity of Deltamethrin on raffia was high. The mortality percentage was above 85% after 360 days and dropped to about 50% at 420 days. The effect of DDT was reduced after 180 days and reached zero by the end of the experiment. Based or the results of these experiments, it is recommended that Deltamethrin be used to spray raffia curtains in mining regions and other areas that are endemic for malaria.