To Prevent Malaria in Humans, Scientists Try Protecting Pigs

For years , scientists have known of a sneaky way to kill mosquitoes: Give humans a deworming pill.

The active ingredient, ivermectin, kills not only worms infesting people but also mosquitoes who drink their drug-laden blood. (Ivermectin also kills lice, bedbugs and other blood-feeders. The drug’s inventors recently received a Nobel Prize in Physiology or Medicine.)

Turning everyone in a village into a walking mosquito bomb, many scientists agree, could stop or slow transmission of malaria, yellow fever, dengue, chikungunya and other diseases.

But villagers with worms normally receive only one or two pills a year. Researchers aren’t certain it is possible — or safe — to boost blood levels of ivermectin high enough to wipe out generations of mosquitoes during the biting season, which can last for months.

Scientists at the medical school of the University of Barcelona have come up with a novel alternative: Use livestock.

In a poster presentation at a meeting of the American Society of Tropical Medicine and Hygiene in Philadelphia last week, the researchers showed how they had implanted two-inch soft silicone rods releasing a steady dose of ivermectin under the skin of pigs.

Many poor farmers keep their animals near or even inside their homes to protect them from predators or thieves.

Some disease-carrying mosquito species alternate between biting animals and humans, said Dr. Carlos Chaccour, a researcher at the University of Barcelona’s Institute for Global Health and the University of Navarra. Ivermectin will kill most mosquitoes, but the dose needed varies by species.

Because not all poor farmers raise pigs — Muslims, for example, do not — the method will still need to be tested in cattle, goats, camels and other livestock.

Animals usually tolerate high doses of ivermectin safely, Dr. Chaccour said, but must be drug-free for some time before they are safe to eat. For example, cattle should not be slaughtered for food until 90 days after a single deworming treatment, according to guidelines by the United Nations Food and Agriculture Organization.

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