IRS Demonstrates Malaria Reduction in Northern Uganda

Apr 2012
In May 2011, the program successfully reached more than 95 percent of the 922,000 targeted houses, protecting more than 2.8 million residents.
Okello PE, Van Bortel W, Byaruhanga AM, et al. 2006. Variation in malaria transmission intensity in seven sites throughout Uganda. American Journal of Tropical Medicine and Hygiene, 75:219-25

Since its launch in Uganda in 2006, PMI has supported implementation of a high quality IRS program in Northern Uganda’s 10 districts, an area of intense malaria transmission. Two rounds of spraying are implemented each year, just prior to the peak malaria transmission seasons. In May 2011, the program successfully reached more than 95 percent of the 922,000 targeted houses, protecting more than 2.8 million residents.

During the first rounds of spraying, in 2007–2009, the IRS program primarily used pyrethroids, except in Apac District, where DDT was used for the first spray round. Apac District is known to have one of the highest number of infectious mosquito bites per person per year (see graph). Despite multiple rounds of spraying, only modest decreases in the slide positivity rate were seen. After insecticide resistance surveillance demonstrated resistance to both DDT and pyrethroids, the program switched insecticide classes to carbamates (bendiocarb) for the 2010–2011 spray seasons. An analysis of health facility data at Aduku Health Center IV in Apac District showed a sharp decrease in malaria cases. After three rounds of spraying, slide positivity rates for malaria fell from 74 percent in August 2010 to 34 percent in August 2011 among children under five years of age and from 42 percent to 33 percent among those over five years of age. Similarly, reported malaria cases decreased significantly in St. Joseph’s Hospital in Kitgum and Lacor Hospital in Gulu, where slide positivity rates for malaria dropped from 60 percent to 20 percent and from 38 percent to 5 percent after three consecutive spraying rounds, respectively. These results show not only the high effectiveness of IRS as a malaria control measure, but also the crucial need for IRS programs to monitor insecticide resistance so that changes in insecticides can be made in a timely manner.

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