Increased Rate of Malaria Transmission found following Severe Flood Event in Western Uganda

by Hogan Marhoefer

As climate patterns and weather conditions continually change as a result of global warming, it is increasingly important to understand how these climate changes impact global health. Several areas of vector-borne disease control are very well-understood, however the influences of climate change on vector-borne disease transmission are understudied but very relevant. It is well-known that malaria is transmitted by mosquitoes and increased transmission rates relate to the success of local mosquito populations. It has also now known that global warming has contributed to increased precipitation and warmer weather in many regions, which provide a more favorable environment for mosquito reproduction success (due to increased precipitation). It is apparent that precipitation greatly influences disease transmission in Malaria, however temperature plays an equally influential role in vector-borne disease transmission. As temperatures rise, mosquito populations are able to occupy regions of higher altitude as they are no longer restricted by regions of cooler temperatures These factors are of great importance to this study because a significant number of the rural communities in the Kasese District are at relatively high elevation, and have experienced heavy rainfall.

Boyce et al. (2016) examined the changes in rates of malaria transmission following a significant flooding event in the Western Ugandan Highlands to better understand how transmission rates of malaria are affected by severe changes in local climate patterns. This study is not only pertinent to a better understanding of how severe flooding events can influence transmission rates but also sheds light on how even moderate increases in precipitation levels could potentially impact malaria transmission. Researchers analyzed data from the 12-month period directly before and after the severe flooding event, which they collected from the Bugoye Level III Health Center (BHC). The researchers chose to focus on the P. falciparum test positivity rate (or PfPR) and the “incidence rate of severe malaria” to asses the impact of the 2013 flooding event on malaria transmission.

The study found that the test positivity rate (PfPR) had increased from 25.8% to 39.4% from the preflood to the postflood period. The analysis of PfPR by month illustrated that the most significant increase had taken place during the month of November, noteably a low transmission period. In addition, researchers found that postflood PfPRs were significantly higher in villages that bordered flood-affected rivers. It was found that flood-effected rivers were present in all of the eight villages where significant changes in malaria risk had been seen, suggesting that villages in closer proximity to flooding rivers are more vulnerable to malaria transmission. This article highlights the need for more research to examine the disease control implications of other severe weather events as well as developing a better understanding of the magnitude of effect on transmission that could be seen by mere changes in precipitation levels resulting from global climate change.


Ross Boyce, Raquel Reyes, Michael Matte, Moses Ntaro, 2016. Severe Flooding and Malaria Transmission in the Western Ugandan Highlands: Implications for Disease Control in an Era of Global Climate Change. The Journal of Infectious Diseases (2016) 214 (9): 1403-1410.





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