Studies on malaria in Serra do Navioegion, Amapa State, Brazil

This study evaluated the status of malaria transmission in Serra do Navio region where a malaria control programme had been carried out for more than 20 years, which included the provision of a daily intake of chioroquinised salt. Malaria endemicity in the study areas [target area: Serra do Navio (SNV); control areas: Colonia Agua Branca (CAB), Porto Terezinha (PT) and Arrependido (ARR)] was established based on the spleen rate and prevalence of malaria parasites among the 2-9 years age group. SNV was defined as a non-endemic area for malaria since both rates were zero, while CAB and ARR were concluded to be mesoendemic areas since the rates were between 10 and 50%, and PT was considered hypoendemic area because both rates were under 10%. Antibody prevalence measured using IFAT with asexual form antigens of Plasmodium .falciparum and Plasmodium vivax and ELISA (asexual forms of P.falciparum, sporozoites of P.falciparurn, P.vivax type 1, P.vivax type 2, P.vivax type 3 and P.malariae/P.brasilianum) was determined for individuals from each study area. These results showed a high frequency of P.falciparum antibodies in all areas. The level of haptoglobin in 100 children from all these areas demonstrated the close relationship between hypohaptoglobinaemia and malaria in the control areas. Haskin's method , a qualitative method, was applied for testing chioroquine in urine. Therefore, chioroquine levels were measured in serum and urine using the ELISA test and the results were in agreement with the reports of the intake of chioroquine salt. The distribution and potentiality of the malaria vectors in all areas was determined. Fifteen anopheline species were identified among 3053 mosquitoes collected by human biting catches in the 4 study areas. 96.4% of the total mosquitoes caught belonged to 4 species, namely, An.albitarsis, An.braziliensis, An.nuñeztovari and An.triannulatus. An.darlingi which is considered the main vector of malaria in the Amazon region of Brazil was very scarce. Using ELISA for the detection of Plasmodium spp sporozoites a positivity rate of 0.799% (23/2876) was found covering six species: 15 An. albitarsis, 4 An. nuñeztovari, and 1 of each: An. braziliensis, An. triannulatus, An. oswaldoi and An.rangeli. 9 out 23 positive mosquitoes were infected with P. raalariae ; 9 with P. vivax- variant VK 247; 3 with P. falciparum and 2 with the classical P.vivax.