Linking rainfall and irrigation to clinically reported malaria cases in some villages in Chikhwawa District, Malawi

Abstract

Irrigation is a major coping strategy in many areas experiencing unreliable rainfall distribution and pattern for rain fed agriculture. The benefits of irrigation may however be challenged by its potential to increase malaria incidences through creating breeding grounds for malaria vectors. This study compared malaria trends from archived malaria records in the rainy season and the dry season in Mbewe Extension Planning Area (EPA) in Chikhwawa District, Malawi. This is an area where irrigation has been intensified as a means of coping with floods and drought effects, which often result in crop destruction and failure. Data of monthly incidences of malaria from 2002 to 2009 from Ndakwera Health Centre in the area were used. Rainfall data for the area from 1971 to 2008 were also used. Mwanza River discharge from 1951 to 1992 was considered. Rainfall data were lagged to four months taking into consideration the breeding period of malaria vectors and the incubation period for malaria in human host. We assessed correlation between rainfall and malaria using data of 2004–2009, by fitting a generalised linear model to the data via an over-dispersed Poisson model. The highest malaria cases corresponded with the rain season. Malaria cases in the dry season, when irrigation is implemented, were low. The Pearson correlation coefficient for the monthly rainfall and discharge was not statistically significant at 0.34 (p > 0.05). The results suggest that direct contribution of the rainfall to flooding in the area is minimal and the floods experienced are generated in the upstream areas. Further, the malaria pattern was mainly associated with the rain season flooding and not irrigation