Malaria: past failure, continuous challenge

Washington, DC, August 29, 2002 (PAHO) -- Malaria, a tropical disease that has perplexed scientists and infects 300 million people per year, is one of the most complex health problems facing humanity. Since a past eradication attempt failed and vaccine development has not yet succeeded, the disease is a continuing challenge to public health experts.

"Despite earlier successes in shrinking the disease's geographical boundaries, malaria control today is more difficult than ever. Much of the increased risk is linked to changes in land use, such as road-building, mining, logging, agricultural and irrigation projects, particularly in frontier areas such as the Amazon," according to Dr. George Alleyne, director of the Pan American Health Organization (PAHO).

"This initiative represents a global association among countries affected by malaria, the United Nations, bilateral development agencies, development banks, nongovernmental organizations, and the private sector," explained Dr. Keith Carter, regional adviser on malaria at the Pan American Health Organization. "The purpose of this collaboration is to reduce the overall burden of malaria through interventions adapted to local needs and strengthening of the health sector."

Today, malaria is endemic in the region, transmitted actively in 21 countries and territories of the Western Hemisphere. Of the 300 million infected annually worldwide, more than one million persons die and several million remain sick.

"This initiative did not start from scratch, but was based on previous efforts and the global strategy for malaria control. The main goal is to reduce by 50 percent the mortality associated with this affliction," said Dr. Carter. "The member countries of PAHO have achieved some success in reducing mortality, from 806 deaths in 1994 to 201 in 1998."

"The initiative proposes nothing less than a major assault on the disease, backed by a unified political commitment" that requires the contribution of "families, schools, businesses, the health, environment, water supply and sanitation sectors" and all those whose activities directly or indirectly affect the malaria situation," said Dr. Alleyne.

Apart from some limited achievements, the battle against malaria has been a failure to date, since the global program for eradication launched in 1956 was abandoned, after an investment of millions of dollars and the work of thousands of health workers.

According to Dr. Carter, to analyze the failure of the eradication program, multiple combinations of variables must be taken into account: the parasites that cause the disease, the mosquito vectors, human susceptibility to illness, people's behavior and knowledge, socioeconomic activity and environmental factors. These factors all influence the conditions for malaria.

"Some early and successful attempts to control some species of the numerous mosquito vectors, along with the availability of DDT, an excellent insecticide, stimulated the hope in the 1940s that combating mosquitoes could lead to the eradication of malaria," said Dr. Carter. "Very little attention was paid to other variables within clear epidemiological contexts, and this led to the failure of the eradication program," he noted.

In order for the new initiative to succeed, Dr. Carter says, rational use is being made of current and future instruments to control the disease, taking advantage of the knowledge of local epidemiological conditions in the context of the overall strategy of control of the disease.

Priority one in malaria control is early diagnosis and immediate treatment, since a person with fever can die from malaria in a matter of 12 hours. Furthermore, severe cases can require intensive care that is extremely expensive. On the average, each case of malaria results in two months of lost income, say PAHO experts.

After more than 30 years, researchers have still not been able to find a vaccine against this disease. "There are four malaria parasites that affect humans" explains Dr. Carter. The parasites have different structures and states of development in their life cycle, including different stages of development in mosquitoes and in men." Obviously this has slowed vaccine research, although studies continue.

PAHO, which also serves as the Regional Office for the Americas of the World Health Organization, was established in 1902 and is the oldest health organization in the world. It works with all the countries of the Americas to improve the health and raise the living standards of their peoples.