New Vaccines Offer Hope for Malarial Countries
Posted February 1, 1998
Here in the United States mosquitoes are mostly a nuisance, but in many areas of the world they are a harbinger of death because fully one-third of Earth's human
population lives in zones at risk of catching malaria. Although malaria is considered a tropical disease, Anopheles mosquitoes, which carry the disease, live throughout the United
States in the summer.
Malaria is caused by a protist sporozoan in the genus Plasmodium. The protist has a complex life cycle with stages in Anopheles mosquitoes and humans.
Symptoms of malarial infection include recurring fevers, chills, and anemia. Without treatment, many people die. Every 12 seconds a child under the age of five dies from malaria, with
a total death toll between 2 and 4 million people per year, many times more than the number who die of AIDS. More than 300 million people are presently infected with this mosquito-transmitted
disease.
Malaria is resurging in many countries in which it had been eliminated or sharply reduced after campaigns to eradicate mosquitoes. Also, the sporozoans are becoming
increasingly resistant to the primary drugs used to prevent infection, such as chloroquine and primaquine. As the organisms evolve resistance to drugs, scientists are searching for new
means of controlling disease.
A new weapon in the war being waged on this killer is a vaccine. Approaches to developing a vaccine may be aimed at any of the three stages of the protist's life cycle.
A multistage vaccine has shown promise in animal studies, and DNA vaccines offer another approach. Recently malaria researchers were excited by the preliminary evaluation of a vaccine
developed by the U.S. Army and SmithKline Beecham Biologicals. The vaccine is based on the major surface protein of the protist stage that infects liver cells. Large reductions in the
numbers of infected individuals have also been seen in areas where people have used insecticide-impregnated mosquito netting around their beds. Some scientists think that a useful vaccine
may be developed, tested and in widespread use within five to 10 years.
References
Nature, April 10, 1997, Malaria Database, World Health Organization
http://www.wehi.edu.au/biology/malaria/who.html
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