Drug Long Used by Vets Could Boost Fight Against Malaria

BY Talea Miller  July 7, 2011 at 10:16 AM EDT


Infant surrounded by mosquito nets. Photo by World Bank.

A drug commonly used to combat heart worms in pets in the United States is becoming a versatile parasite-fighting treatment in regions stricken by tropical disease.

Ivermectin, developed decades ago as a veterinary drug, has already been proved effective in humans against river blindness, a disease caused by worms that invade the eyes. It has also used in campaigns in sub-Saharan Africa against elephantiasis, which is caused by parasitic worms and causes severe swelling of the limbs.

Now new research shows the drug could be a force against malaria, which kills 1 million people around the globe each year.

Distributing Ivermectin throughout a community in Senegal appeared to disrupt malaria transmission and kill off mosquitoes carrying the parasite, a study released late Wednesday in the American Journal of Tropical Medicine and Hygiene shows.

Two weeks after Ivermectin was given to the inhabitants of one village, researchers observed a 79 percent decline in mosquitoes carrying the malaria parasite. In a control village, where the drug was not given out, the number of parasite-carrying mosquitoes more than doubled in the same period. Malaria is caused by the Plasmodium falciparum parasite that lives in an infected person’s blood, and is transmitted to new victims by mosquitoes.

“If using Ivermectin works to reduce transmission, people will have a drug circulating in their blood that could kill mosquitoes anywhere and at any time of day,” said Brian Foy, the lead author of the study and a vector biologist at Colorado State University. Currently malaria transmission prevention is largely reliant on insecticide-treated bed nets used at night or the spraying of homes with insecticide.

The research team called for additional study to help determine how long the transmission effect would last in a population and what the drug could do in a larger area, but said the results show potential to be especially valuable for “reducing malaria parasite transmission during epidemics or…malaria transmission seasons.”

“The fact that the mosquitoes, their life is shortened by taking blood from somebody who is treated [with Ivermectin], is quite significant,” said Clive Shiff of the Malaria Research Institute at Johns Hopkins University, who was not involved in the study. “How it could be applied in public health is another thing altogether.”

“The money they make on it in developed countries enables Merck to make this generous gesture, to make it free of charge or at little charge for onchocerciasis [river blindness] control,” he said. A prevention campaign for malaria, which affects larger populations, would be a much larger effort and would also likely mean administering the drug quite often, at least once a month, the researchers project.

Ivermectin is usually distributed once or twice a year for river blindness and once a year for elephantiasis.

“The fact that it works is very nice but the next thing to do is to find out if it’s economically feasible,” Shiff said.