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Treating Whole Villages with Common Anti-parasitic Drug Could Help Fight Malaria


Study Shows One Dose May Thwart Three Parasitic Diseases


Summary

Community-wide administration of ivermectin, a safe and widely available anti-worm drug, was found to reduce malaria-infected mosquito populations and disrupt the transmission of malaria to humans in several villages in Senegal, West Africa, according to researchers at Colorado State University. The research was funded by NIAID.

Background

Photo of Brian Foy, Ph.D., holding a box of mosquitoes that have been aspirated from huts and prepared for transfer to a field insectary.
Brian D. Foy, Ph.D. of Colorado State University, holds a box of mosquitoes that have been aspirated from huts that morning. A wet towel keeps the mosquitoes cool and undisturbed before transfer to a field insectary. Behind him is researcher Massamba Sylla, Ph. D., wearing a backpack mosquito aspirator. Photo credit: Kevin Kobylinski

Ivermectin currently is used to control the parasitic worms that cause the tropical diseases onchocerciasis, also known as river blindness, and lymphatic filariasis, also known as elephantiasis. In tropical areas of the world where these two diseases are common, health authorities treat entire communities with a single dose of ivermectin at the same time in a strategy known as mass drug administration (MDA). MDAs typically reach about 70 to 80 percent of the community members, because ivermectin is not advised for pregnant women, people with chronic illnesses and children weighing less than 15 kilograms (about 33 pounds).

Results

In their small study in Senegal, the researchers collected mosquitoes in three villages where ivermectin MDA had taken place. In these villages, among all mosquitoes collected, the research team measured a 79 percent decrease in the average proportion of malaria-infected mosquitoes for two weeks after ivermectin MDA. In three matched control villages that did not receive ivermectin, there was a 246 percent increase in the average proportion of malaria-infected mosquitoes among all mosquitoes collected during the same time.

Significance

As described in the July 2011 issue of Journal of the American Society of Tropical Medicine and Hygiene, the discovery that ivermectin reduces the prevalence of malaria-infected mosquitoes may be useful in timing MDAs to maximize their beneficial health effects in communities that are simultaneously affected by malaria, onchocerciasis and elephantiasis. It is also possible, they say, that adding community-wide treatment with ivermectin to other malaria control programs may boost their effectiveness, providing another tool in the fight against malaria around the world.

Next steps

The study was designed to determine whether malaria-infected mosquitoes were killed after feeding on people treated with ivermectin MDA. The researchers say they were surprised to measure such a significant reduction in malaria-infected mosquitoes in the treated villages, but that more studies are needed to determine the pattern and duration of malaria control beyond two weeks.

References

Short Report: Ivermectin Mass Drug Administration to Humans Disrupts Malaria Parasite Transmission in Senegalese Villages.  American Journal of Tropical Medicine and Hygiene DOI: 10.4269/ajtmh.2011.11.11-0160 (2011).

NIAID Vector Biology Research

NIAID Malaria Research

Last Updated August 12, 2011

Last Reviewed August 05, 2011