Temporal and spatial patterns of malaria reinfection in northeastern Venezuela

We stratified the risk of malaria transmission (Plasmodium vivax) in 35 vil lages along a coastal range in northeastern Venezuela (51 km(2)) where the main vector is the mosquito Anopheles aquasalis. After 20 years without loc al malaria transmission, reinfection of the entire area occurred from May t o December 1985 by local (continuous) and jump (discontinuous) dispersal. E pidemiologic, environmental, and vector variables were investigated with th e aid of a Geographic Information System. Risk factors for malaria transmis sion were human population density, proximity to pre-adult mosquito habitat s (( 500 m), and the number of pre-adult habitats nearby. Most inhabitants, immature mosquito habitats, and malaria cases were located at low elevatio ns and on gentle slopes. High prevalence of malaria during the dry seasons was associated with the presence of permanent bodies of water containing An . aquasalis. Occurrence of a La Nina event in 1988 (wet and cool phase of t he El Nino Southern Oscillation) triggered malaria transmission to unusuall y high levels, consolidating infection in the area, and rendering tradition al control efforts useless. We recommend tracking malaria persistence per v illage and associated risk factors as methods to reduce the cost of malaria control programs.