Malaria and Land Use: A Spatial and Temporal Risk Analysis in Southern Sri Lanka

Abstract

"Malaria in Sri Lanka is unstable and epidemic, with large spatial and temporal differences in transmission dynamics. The disease is of great public-health significance and, hence, identification of underlying risk factors is important to target the limited resources for most cost-effective control of the disease. Health-seeking behavior in Sri Lanka is primarily in government-based facilities, with malaria-incidence rates reported in a systematic manner. Recently, the International Water Management Institute launched a project of malaria risk mapping in Sri Lanka to investigate whether this tool could be utilized for epidemic forecasting. We present the first results of the study for the Uda Walawe region in southern Sri Lanka. Data on aggregate malaria-incidence rates, land-and-water -use patterns, socioeconomic features and malaria-control interventions were collected and put into a geographical information system. Malaria cases were mapped at the smallest administrative level, namely the Grama Niladhari Division. Relative risks for different variables were calculated employing multivariate analyses. Areas of high malaria risk were characterized by a) more than average rainfall, b) a large forest coverage, c) chena (slash-and-burn) cultivation, d) the presence of abandoned tanks, and e) a poor socioeconomic status. The risk of malaria in irrigated rice cultivation areas was lower than in other areas. People performing irrigated agriculture generally have higher socioeconomic, nutritional and health indicators, live in better-constructed houses, and use preventative measures more frequently, and these might explain their lower malaria risk. However, ecological idiosyncrasies in malaria vector density or species composition might also account for this difference. Our findings call for malaria-control strategies that are readily adapted to different ecological and epidemiological settings. Malaria risk maps are a convenient tool for discussion with control personnel and for assisting them in targeted and cost-effective interventions."