HYPOENDEMIC MALARIA IN RONDONIA (BRAZIL, WESTERN AMAZON REGION) - SEASONAL-VARIATION AND RISK GROUPS IN AN URBAN LOCALITY

A longitudinal epidemiologic survey (1989-1991) plus a cross-sectional parasitologic, clinical, and sociodemographic survey (July-October 19 90) were conducted in Candeias do Jamary, a village with approximately 7,000 inhabitants in Rondonia, Brazil. Analysis of the results reveal ed hypoendemic malaria with a complex epidemiology. Plasmodium vivax p redominated over P. falciparum infections while infections with P. mal ariae were absent. Malaria is present throughout the year but was clea rly seasonal with epidemic outbreaks in the dry season from June to Au gust. Malaria prevalence was lower in children less than 10 years of a ge and significantly higher in young adult males, which represent the high-risk group. The incidence of locally acquired infections (autocht honous cases) was significantly lower in the rainy season as compared with the dry season. This is not true with respect to heterotochthonou s (imported) malaria cases, that is, malaria acquired elsewhere by Can deias residents, most of whom are male adults working outside the town . In both cases, however, the age and sex distribution of prevalence a nd its relationship with occupational activities indicate a predominan ce of outdoor transmission. The results of the cross-sectional survey are in agreement with those of the longitudinal passive survey and, in addition, disclose the absence of asymptomatic infection.