Epidemiology of the malaria in communities of the river Padauiri, medium Black river, an area of vegetal extraction of piaçaba in the State of Amazon, Brazil.
The Padauiri River - a tributary of Rio Negro in the Amazonas state - is a ?piaçaba? extraction area located in a high endemic malaria region. In this study, an investigation of the local epidemiology, which has not been previously reported, wasaccomplished. In order to establish Plasmodium infection prevalence, malaria new cases and to determine risk factors we conducted a cohort study (n=188) after carrying outbasic epidemiology researches in that area (a retrospective analysis and a cross-sectional study). Following a questionnaire and physical examination of all local inhabitants, bloodsamples were collected for carrying out thick and thin smears, DNA extraction for molecular diagnosis and serological probes. Simultaneously, entomological studies were conducted to figure out the main vectors and their behavioral. Breeding water collections were also searched for in the surrounding forest. Malaria case was defined as the patients presenting signs and symptoms of malaria disease with at least one of thehuman Plasmodium parasite determined by thick smear. Asymptomatic infection was defined as carriers of Plasmodium parasite - observed by thick smear and/or positive PCR- without presenting symptoms before or after 30 days of the blood sample collection. Asymptomatic carriers could not have used antimalarial drugs in the last 30 days beforeblood collection. During the follow-up period, any death or hospital admission caused by malaria was registered in the area in the cohort. A total of 53.2% (100/188) ofinhabitants had malaria with 169 malaria episodes. The Annual Parasitic Incidence (API) was 602.3 / 1000 inhabitants. The mean of malaria episodes was 1.7. Children lt;5 yearsold showed higher risk for disease compared with older people (RR: 1.64, CI95%=1.26- 2.14, p=0.012). The mean of malaria episodes in those children was 2.2. P. vivax wasthe main parasite detected in this cohort, which showed an epidemiology changing pattern. Interestingly, P. falciparum was the prevalent parasite in the last decade. Wefound asymptomatic Plasmodium infections (both P. vivax and P. falciparum) ranging from 8.2 to 24.0%. The clinical malaria episodes were seasonal with a trend to occur inthe beginning and end of the rainy season. Asymptomatic infection was more frequent in the dry season. The most important insect vector in the studied area was the Anophelesdarlingi with epidemiological regional differences. The probability of capture the vector was higher in the ?piaçaba´s? areas. In this place of the Amazonian region, An. darlingihas predominantly endofagic behavioral. The main determinant risk for parasite transmission was geographical localization. The population living in localities near at the ?piaçaba? collocations had more malaria cases and asymptomatic Plasmodium infections. Likewise, An. darlingi was found inside of the dwellings although permanent breedingwater collection was not observed in the surrounding area. On the other hand, only temporary breeding water collections were found with anophelines immature phases. Weobserved differences in the malaria prevalence and asymptomatic Plasmodium infection along the few kilometers within the researched area. Diverse malaria situations wereobserved in a small geographical space limiting the control strategies. It is crucial to apply different malaria control strategies for each transmission area.
Advisor:José Rodrigues Coura
School:Faculdades Oswaldo Cruz
Source Type:Master's Thesis
Date of Publication:04/11/2007