While highly effective in controlling the mosquito population, there are serious drawbacks to the use of DDT.
The good news is that the results of a new project carried out in Mexico and Central America show that the fight against malaria does not have to depend on using DDT. In Mexico and the Central American countries, it is estimated that around 108.7 million people live in areas that are environmentally favorable to the transmission of malaria, and 35 percent of them are at high risk of contracting the disease.
The need to continue to rely on DDT to effectively combat malaria has been the subject of a long running discussion. Although DDT spraying has long been successfully used in controlling the mosquito population and the spread of malaria, it easily enters the food chain and persists for many years in the environment. The result is often serious harm to wildlife. In addition, the mosquito population under attack can become resistant to DDT, making necessary the search for alternatives.
Since 2004, a project funded by UNEP (United Nations Environmental Program) and GEF (Global Environmental Facility) has been carried out with the technical support of the Pan American Health Organization (PAHO) in Mexico, Belize, Costa Rica, Guatemala, Honduras, Nicaragua, El Salvador, and Panama. It was developed based on the strategies outlined in the Roll Back Malaria approach championed by the World Health Organization.
This project was initially implemented in Mexico and subsequently it was adopted—with changes according to local circumstances—in the Central American countries. Critical to its success have been the use of public health measures aimed at controlling the mosquito breeding and standing sites, rapid diagnosis and treatment of those affected with malaria, and active community participation.
Public health measures against malaria had already shown their effectiveness in Central America. During the construction of the Panama Canal, which had been abandoned by the French in 1889 due to financial scandals and the high numbers of workers’ deaths due to malaria and yellow fever, thousands of lives were saved thanks to public health measures implemented by Dr. William C. Gorgas, from the U.S. Army Medical Corps.
Similar public health measures in the Mexico/Central America project include participatory community treatment of larval breeding sites, improving housing conditions, periodical clearing of vegetation around the houses, and elimination of stagnant water deposits near the houses. These actions are complemented by a wide array of educational interventions aimed at improving knowledge about malaria transmission, and rapid diagnosis and prompt treatment of those affected in the community.
Early detection and treatment is critical to eliminate the parasite carriers. An important aspect of this project has been the collaboration of voluntary community health workers who are taught to make an early diagnosis in situ and to administer complete courses of treatment not only to those affected but also to the patients’ immediate contacts.
The project was carried out in specific pilot areas called “demonstration areas” which had been selected due to their high levels of malaria transmission. In those areas, the number of malaria cases fell 63% from 2004 to 2007. In several demonstration areas I visited in Honduras and Mexico as a consultant for the Pan American Health Organization malaria had practically been eliminated. Plans are underway to expand the project to other regions where malaria remains a serious threat.
One of the advantages of not using DDT (besides avoiding its toxic effects) is the enormous savings realized from discontinuing its routine use. These savings can now be put to good use with other diseases.
Although DDT can still be used in some countries or regions with extremely high levels of malaria infection, the fact that an effective campaign against malaria can be waged without it, and at much lower cost, raises hopes that this approach can be used as time goes on by a wide range of developing countries not only in the Americas, but in Africa and Asia as well.
Dr. César Chelala is an international public health consultant.
