Malaria, a tropical disease that has been called one of the most complex health problems facing humanity in the 20th century, is at once a failure, a puzzle, and a serious challenge, according to the Pan American Health Organization.
The latest issue of PAHO's Perspectives in Health magazine notes that the fight against malaria to date has been a failure because a worldwide eradication program that began in 1956 subsequently was abandoned, but only after the expenditure of millions of dollars and the efforts of thousands of health workers. Malaria remains a puzzle because researchers have not found a vaccine after 30 years of trying. And malaria presents a challenge because it still infects 300 million people a year in the world, kills over one million of these annually, and leaves millions more sick and debilitated.
Today malaria is transmitted actively in 21 countries and territories in the Western Hemisphere. But a new program, Roll Back Malaria seeks to cut deaths from malaria in half by the year 2010, according to Dr. Renato Gusmao, malaria expert for PAHO. The plan aims to reduce malaria incidence by controlling transmission, using community health workers to help diagnose and treat the disease.
PAHO Director Dr. George Alleyne says that "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."
In a column for the magazine, Dr. Alleyne notes that the Roll Back malaria 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, environmental, water supply and sanitation sectors" and all those whose activities directly or indirectly affect the malaria situation.
The magazine notes that different approaches to a malaria vaccine are being tried but it could take seven to 15 years before one is ready. Captain Stephen L. Hoffman of the U.S. Naval Medical Research Institute says: "Malaria vaccine development is the Number One ranked Department of Defense medical research, infectious disease, science, and technology objective, because malaria has been responsible for enormous numbers of casualties during military campaigns."
Several vaccine candidates using the latest breakthroughs in vaccine technology are in field tests in Asia and Africa and in U.S. volunteers and on another front, the whole genome "a complete set of hereditary factors" of the malaria parasite is being sequenced
A vaccine against malaria would not only benefit vulnerable populations living in malaria-endemic regions but also tourists and military forces in affected areas.
Vaccines taking advantage of DNA research may provide one of the best hopes. One possibility is being developed by the U.S. Naval Medical Research Institute, the U.S. Agency for International Development, the U.S. private sector, and partners in Ghana, Australia, and France. Hoffman recently published the first proof of the principle that DNA vaccines can produce immunity in normal, healthy humans. On April 30, 1998, physicians conducting the first human trial of a DNA vaccine against malaria reported that it was well tolerated and safe. The next phase of clinical testing will include assessment of protective efficacy against malaria. Vical Inc. and Pasteur Merieux Connaught sponsored the trial.
Other promising vaccine candidates are under development, the PAHO magazine noted. One is a recombinant protein vaccine developed by SmithKline Biologicals that would prevent the malaria parasite in its infectious stage from entering or developing within liver cells of human beings, thus blocking the severe and life-threatening consequences of malaria in non-immune individuals. Another is a transmission-blocking vaccine being developed by NIH scientists. Meanwhile, in Colombia, Dr. Manuel Elkin Patarroyo has developed a synthetic peptide vaccine called SPf66 that has undergone field trials in South America, Africa, and Southeast Asia. It only has been partially effective to date, and Dr. Patarroyo is working to improve its potency.
"The key priority in malaria control is early diagnosis of malaria cases and immediate treatment," says Gusmao. "In a matter of 12 hours, a person with a fever can succumb and die from malaria. A person who is stricken by severe malaria can go into a coma and require intensive care, which is extremely costly. And each case of malaria, on the average, results in an average of two months of lost income." Gusmao says several things must be done to reduce death and disease from malaria. Apart from the key responses of early diagnosis and rapid treatment, measures to prevent transmission include mosquito control, environmental cleanup, and better housing offering more protection from mosquitoes. Effective control programs must take into account local conditions and engage the community at large with improvements and access to basic health services.
In the Americas, Gusmao said, resource networks are being set up to improve collaboration, communicate lessons learned, prevent and control epidemics, provide anti-malaria drugs, and monitor resistance to drugs and insecticides. PAHO has launched a revolving fund to buy drugs and insecticides with a grant from the Government of Brazil. But more financing is needed, says Gusmao, "in order to roll back malaria in the Region of the Americas."
Dr. Keith Carter, who headed Guyana's malaria program before moving to work for PAHO in Guayaquil, Ecuador, said: "On the whole, we could probably state that slight progress has been made through increasing diagnostic and treatment facilities and in preventing the number of complicated cases and deaths. I think we need to bear in mind the fact that the disease is endemic in the Region and that there are no efforts to eradicate it." Bed nets have been touted as one solution in the prevention of malaria transmission, especially if they are treated with insecticides. But getting people to use them may be difficult, Carter says. "If people normally use bed nets, they do so at night. If the malaria vector's peak biting period is at night when people are most likely under the nets, these will help reduce man-vector contact and theoretically reduce transmission."
For further information contact: Daniel Epstein, tel: 202-974-3459, fax: 202- 974-3143, Office of Public Information, email: epsteind@paho.org, /www.paho.org.