Epidemiology of Resurgent Malaria in Eastern Zimbabwe: Risk Factors, Spatio-Temporal Patterns and Prospects for Regaining Malaria Control

Mufaro Kanyangarara and her PhD thesis adviser, Luke Mullany, of the Johns Hopkins Bloomberg School of Public Health Department of International Health, have been looking into the challenges of controlling and eventually eliminating malaria in a multi-country context in southern Africa. We are sharing abstracts from her pioneering work. The first seen below provides an overview of the three components of the study.

Incidence 2012Despite recent reductions in malaria morbidity and mortality due to the scale up of malaria interventions, malaria remains a public health problem in sub-Saharan Africa, especially among children under five years of age, pregnant women and people living with HIV/AIDS. A recent resurgence in malaria, in areas where malaria control was previously successful, has brought to the forefront the importance of research to understand the epidemiology of malaria and the effectiveness of malaria control efforts in resurgent settings. Using cross-sectional surveys, routine data from health-facility based surveillance and freely available remotely sensed environmental data, this research examined the distribution of malaria and the impact of vector control in Mutasa, a rural district in Zimbabwe characterized by resurgent malaria.

Firstly, individual- and household level factors independently associated with individual malaria risk were identified using multilevel logistic regression models based on data from cross-sectional surveys conducted between October 2012 and September 2014. Secondly, geostatistical methods and remotely sensed environmental data were used to model the spatial and seasonal distribution of household malaria risk; then develop seasonal malaria risk maps with corresponding maps of the prediction uncertainty. Lastly, an evaluation of the effect of introducing an organophosphate for indoor residual spraying was conducted using routine health facility data covering 24 months before and 6 months after the campaign.

The results of multilevel model suggested that malaria risk was significantly higher among individuals who were younger than 25 years, did not sleep under a bed net, and lived close to the Zimbabwe-Mozambique border. The spatial risk maps depicted relatively increased risk of finding a positive household in low-lying areas along the Mozambique border during the rainy season. Lastly, the introduction of organophosphates to this pyretheroid resistant area resulted in a significant reduction in malaria incidence following spraying. These findings elucidate the heterogeneous distribution of malaria, identify risk factors driving malaria transmission and assess the quantitative impact of switching insecticide classes on health outcomes. Collectively, the findings provide evidence to guide country-specific decision making for regaining malaria control and underscore the need for strong between-country initiatives to curb malaria in Mutasa District and elsewhere.

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