Decline in use for DDT vector control

In many countries, disease vector control has moved away from large, centrally organised programmes to regional or district-based programmes(1).  
    The older insecticides are still the mainstay of vector control. DDT, for example, is widely used for malaria and leishmaniasis vector control. But the World Health Organisation (WHO) now says it no longer merits DDT as 'the insecticide of choice' for vector control.
    The Mexican government will phase out all uses of the organochlorines DDT and chlordane within 10 years(2). There will be an 80% reduction in the use of DDT over the next five years, culminating in a total phase out by 2007. Chlordane use will stop by 2008. Mexico is one of the few remaining countries producing DDT, and the phase out also includes closing the production plant.
    DDT use is declining in Mexico but it is still applied to control the Anopheles mosquitoes that carry malaria.
    The annual incidence of the disease in Mexico has declined from 2.4 million cases in the 1940s and 1950s to 5,000 cases today-while reducing annual domestic production and use of DDT from 25,000 tons to a current production rate of 600 tons.
    The use of the bacterial insecticide (Bacillus thuringiensis) has increased as a response to the need for safe, pest-specific control. Insect growth regulators (IGRs) have also become more widely used over the last 12 years, especially to control mosquitoes. IGRs have a high margin of safety to fish, birds, mammals, and most aquatic non-target species, although some are safer than others. However, some IGRs do adversely affect aquatic crustaceans and species closely related to mosquitoes. 

1. D.C. Chavasse and H.H. Yap, Chemical methods for the control of vectors and pests of public health importance, WHO/CTD/WHOPES/97.2, 1997.  
2. Environmental Health Perspectives, Vol. 105, No 8, August 1997, pp790-791.

[This article first appeared in Pesticides News No. 38, December 1997, page 23]