Why Not DDT?              BioVision position paper 2006

In the last few decades we have seen a dramatic growth in chemical manufacturing and other human activities that result in the release of toxic pollutants into the environment. Some of these activities pose a serious threat to human health and the environment. Of particular importance in pests and vector control is DDT that was extensively used in the 1950’s and 60’s during the malaria eradication campaign.  This otherwise very effective compound was banned globally for agricultural use, but restricted for mosquito control. The specific action of DDT is the blockage of the rate-limiting step in the synthesis of cortisol and other hormones.  DDT was banned because it persists in the environment for a long time before it breaks down, it can travel over long distances in water, it accumulates in the fatty tissue of mammals, and it poisons both human and wild life causing cancers, birth defects and fertility problems.

Recently, there has been a movement to re-introduce DDT in Kenya and other African countries such as Uganda and Tanzania for mosquito control. This is not only dangerous to human health and the environment, but also retrogressive, since Kenya is one of the few countries in Africa that potentially has resources and expertise to control malaria in other ways.  It should be understood that the use of DDT for indoor residual spraying to control mosquitoes is just one of several possible components of integrated vector management (IVM).  In turn, IVM is just one component of integrated disease management. One of the main goals of IVM is to reduce the use of synthetic insecticides whenever possible.  It promotes decision-making criteria and management procedures that ensure the best local mix of alternatives for vector management at a given place and time.

The alternatives are:

• Alternative products to chemical control, i.e., biological agents (pathogens like Bti, Bs), botanicals ( e.g. pyrethrum, neem )
• Alternative methods of vector control such as environmental management and personal protection (new plant based repellents)
• Alternative strategies that are based on scientifically sound criteria, cost-effectiveness analysis and a delivery system compatible with current trends in health sector reforms.

BioVision finances projects focused on IVM to fight Malaria and continues the support of Malaria-pilot projects with the International Centre of Insect Physiology and Ecology. For the last 6 years ICIPE has been developing tools and strategies in the quest for an IVM approach to malaria control that can serve as an alternative to the use of insecticides, specifically avoiding the use of DDT.  These include bioprospecting for adult mosquito repellents and larvicides from plants, development of odor baited traps, testing of Bacillus thurigiensis var. israeliensis and neem for larval control.  The studies on larval ecology at the coast region, lake region and the highlands of Kenya have shown that over 90% of mosquito breeding sites are man-made. This implies that man can reverse this trend and should be aware of the location of these breeding sites. It is easier to control mosquitoes in their sedentary and larval stage, than when they fly out in search of a blood meal.  ICIPE’s efforts in this area have shown that use of Bacillus thuringiensis israeliensis (Bti) and B. sphaericus (Bs) can drastically reduce the mosquito populations.  Bti and Bs have and are being used successfully in western countries to control mosquitoes in nature.  

BioVision feels that it is imperative to address the issue of alternatives such as Bti rather than the reintroduction of DDT  -  a major step backwards that not only will cause new harm to an already stressed environment, but also pull the “rug” from under the development and implementation of alternatives. BioVision also believes in assisting the suffering population immediately. Although intervention was possible years ago with environmentally safe strategies, priorities always went to elusive silver bullets (e.g. new drugs, vaccine).  People have to acknowledge that drugs and insecticide treated bed nets are a needed component in an integrated approach that will and must also include the control of the key factor in malaria, the MOSQUITO.