Relationship between malaria infection intensity and rainfall pattern in Entebbe peninsula, Uganda

Background: This study was to assess malaria prevalence in relation to rainfall pattern in different localities of Entebbe Municipality, Uganda. A cross sectional study was conducted amongst the local community residing in the area from January 2003 to January 2004 to investigate the incidence and intensity of malaria infection. Methods: Thick and thin blood smears were made from each patient with fever (body temperature ≥ 37.5° C). The slides were examined microscopically for malaria parasites. A total of 616 residents aged 2 to 50 years were registered in the study by name, age, sex and residential location. Spearman correlation coefficient (r) was used to evaluate relationship between parasite density, age and body temperature on one hand and rainfall plus parasite density on the other hand. Results: A direct relationship was observed between malaria transmission and monthly rainfall in Entebbe Municipality. About 69.8% of the patients had fever. Parasite density fluctuated according to monthly rainfall pattern. Two peaks of high parasite density was observed, each peak coinciding with a peak rainfall pattern of the bimodal annual rain seasons. There was a negative but significant correlation (r = -0.09271; p < 0.0214) between parasite density and age, suggesting that mature individuals clear parasites more effectively than children. Furthermore, we observed a bimodal peak of mean parasite density in children and adults; peak in children is higher than of adults, each peak coinciding with rainfall pattern. There is also a significant positive correlation between parasite density and body temperature (r = 0.1927; p = 0.0001). However, there is no significant variation in mean parasite densities in the different locations of Entebbe Municipality. Conclusions: Our study confirms rainfall pattern and age influence parasite density and are important determinants of malaria infection and transmission in Entebbe Municipality. Increased parasite density in children is a useful indicator for monitoring intensity of infection. This information is valuable in policy formulation for control of malaria during periods of intense transmission