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Researchers Find Key Link in Malaria Transmission

(Beyond Pesticides, September 4, 2007) Scientists identified an important biochemical piece in the passage of malaria from mosquitoes to humans. If this link in the chain can be broken at its source—the mosquito—then the spread of malaria could be stopped without the use of harmful pesticides or costly drugs.

Mosquito Heparan Sulfate and Its Potential Role in Malaria Infection and Transmission,” published in the August 31 issue of the Journal of Biological Chemistry, contains the findings of the interdisciplinary team led by researchers from Rensselaer Polytechnic Institute. The research group found that humans and the mosquitoes that carry the malaria parasite Plasmodium share the same complex carbohydrate, heparan sulfate. In both humans and mosquitoes, heparan sulfate is a receptor for the Plasmodium, binding to the parasite and giving it quick and easy transport through the body.

Robert J. Linhardt, Ph.D., professor of Biocatalysis and Metabolic Engineering at Rensselaer, led the team. “The discovery allows us to think differently about preventing the disease. If we can stop heparan sulfate from binding to the parasite in mosquitoes, we will not just be treating the disease, we will be stopping its spread completely,” Dr. Linhardt said.

Malaria parasites are specific to their host, Dr. Linhardt explained. Birds, rodents, humans, and other primates all can be infected with malaria, but each species is infected by a different species of mosquito — and each of those mosquitoes is infected by a different parasite. In other words, there needs to be a perfect match at the molecular basis for malaria to spread from one species to another, Dr. Linhardt said. Researchers have long understood this deadly partnership, but the molecular basis for the match had never been determined.

Dr. Linhardt and his collaborators were the first to discover the link between the spread of malaria in humans and heparan sulfate in 2003. Those findings were also published in the Journal of Biological Chemistry. In this earlier study, Linhardt compared the receptors in the liver of humans to those of rodents. The liver is the first organ to be infected by the malaria parasite in mammals. The researchers found that heparan sulfate in the human liver was the unwitting transporter of the disease to the human bloodstream. The receptor found in rodents was a different heparan sulfate.

“The discovery marks a paradigm shift in stopping malaria,” Dr. Linhardt said “Now, we can work to develop an environmentally safe, inexpensive way to block infection in mosquitoes and not have to worry about drug side effects in humans.”

Malaria kills over one million people a year around the world, mostly young children. And the problem is growing, Dr. Linhardt noted. As the global temperatures increase, outbreaks of malaria are being reported higher up the coast of South America and Mexico each year, he said.

“Unfortunately, there is little direct funding on malaria in this country outside of the Bill and Melinda Gates Foundation, because it is not considered a major threat in this country,” Dr. Linhardt said. “We do our research on a shoestring. Malaria research funding needs to move higher up on the scientific priority list.”

The discovery comes one year after the World Health Organization (WHO) announced it supported the indoor use of DDT to control the spread of malaria in developing countries. Governmental agencies in the U.S. and internationally have classified DDT as an agent that can cause cancer and nerve damage, and a host of health effects are well documented. The new research may lead to an effective system of malaria control that is not reliant on harmful chemical compounds.

Source: Environment News Service


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