In Campaign Against Malaria-Carrying Mosquitoes, Ugandan Government Should Monitor And Guard Against Development Of Resistance To Insecticides

Main Category: Tropical Diseases
Article Date: 23 Jun 2008 - 4:00 PDT

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Malaria is the leading cause of death and illness in Uganda, taking hundreds of lives every day, especially among pregnant women and young children. The disease accounts for almost a quarter of all deaths in children under age 5. Last year the Ugandan government began a program to spray insecticide -- including DDT -- inside homes, institutions, and settlements in order to kill or repel the mosquitoes that spread malaria. But the effectiveness of this campaign will be threatened if mosquitoes develop resistance to the insecticides, something that has already happened in many parts of sub-Saharan Africa, including parts of Uganda.

As the Ugandan government continues its program, it should monitor mosquito populations to determine whether they are developing resistance, and manage insecticides in ways that minimize resistance, says a new report from the Uganda National Academy of Sciences. Resistance is inevitable if a single class of insecticide is used over a long period, noted the committee that wrote the report.

The report, produced by consensus from a committee of public health and malaria experts, is the first study to be issued by the Uganda National Academy of Sciences. The academy was launched in 2000 with the objective of providing an independent forum for the exchange of scientific knowledge.

To get a clearer view of mosquito resistance throughout Uganda, the Ministry of Health should confirm previous tests and conduct new ones to determine which insecticides remain effective, the report says. For these tests, the country should be divided into ecological zones based on the species of mosquito and the frequency with which the insects transmit malaria. If resistance is detected in a zone, further tests should be conducted in the specific districts targeted for spraying, and the mechanisms of resistance determined. These results will help guide the choice of insecticide in order to best manage the resistance.

The Ministry of Health also should set up "sentinel" sites to monitor mosquito populations as the program continues, to determine whether the insecticides remain effective over time, the report says. Sites should be dispersed through the major ecological zones, and priority should be given to areas where insecticides have been used heavily in agriculture or past public health campaigns, which would increase the likelihood of resistance.

In addition, the ministry should develop a long-term strategy for minimizing the emergence of resistance and institute strict practices for use of insecticides. These chemicals should be used judiciously and applied using high-quality techniques, the report says. The ministry also should track the use and transport of insecticides, and ensure that they are not illegally diverted to agriculture.

Once an insecticide spraying program is started in an area, it must be sustained over the long term to be effective at protecting public health, the report says. Strong acceptance by communities is essential to the program's success, and the ministry should take steps to build awareness of the campaign and engage communities in dialogue about it. In addition, the ministry should evaluate the effectiveness of its program over time, which will involve collecting data on rates of malaria transmission, the size of mosquito populations, and the length of time insecticides are staying effective in homes, among other variables.

The Ministry of Health and other ministries also should support studies that monitor the concentrations of DDT and other insecticides in the environment and food chain. The same qualities that make DDT a powerful tool against malaria -- the chemical persists despite time and rains, and does not have to be reapplied often -- make it necessary to monitor in the environment for ecological and economic reasons, the report adds.

The Uganda National Academy of Sciences is a participant in the African Science Academy Development Initiative, a joint effort among several African academies and the U.S. National Academies to advance science advice and evidence-based public policy in Africa. A committee roster follows.

National Academy of Sciences

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