Alternate wetting and drying and its influence on zoonotic disease vectors in northern Vietnam : can changing the rice-growing method reduce the presence of Japanese encephalitis virus?

Abstract: Japanese encephalitis is an important disease affecting 70,000 people every year, with young children constituting the major part. Growing rice with alternate wetting and drying (AWD) methodology reduces water consumption at the same time as it contributes to a reduction in greenhouse gas emission. In this study, mosquitoes and mosquito larvae were collected at ricegrowing farmers’ households, comparing the number of mosquitoes at households using AWD with households practicing conventional methods. Mosquitoes were also analyzed with PCR regarding Japanese encephalitis virus. In addition, a survey was conducted at the households, concerning the farmers knowledge about mosquito-borne diseases in general, Japanese encephalitis in particular and their measurements taken to avoid these diseases. In total, 2,072 mosquitoes were trapped, identified and analyzed. No difference in the number of mosquitoes were found between AWD-practicing households and households practicing conventional rice growing. None of the mosquito pools tested positive for Japanese encephalitis virus. Correlations between level of education and knowledge about mosquito-borne diseases were found. Knowledge about these diseases needs to be improved to increase the preventions practiced. This study shows that more research, with a greater number of material and in areas with different constitutions between AWD and conventional rice-growing methods, is needed.