New York Times - Parasites: Learning a worm-killer's modus operandi

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Researchers have finally discovered how ivermectin, one of the most important worm-killing drugs used in both humans and animals for decades, actually works.

Ivermectin, extracted from a soil fungus in the 1970s, was originally sold under names like Heartgard to deworm pets.

In a study posted online in The Proceedings of the National Academy of Sciences, researchers from McGill and Michigan State Universities showed that ivermectin does not kill the worms directly. It binds to proteins secreted by young worms to block the host’s immune system. With the worm’s defenses down, white blood cells move in for the kill.

Luckily for humans, said Charles D. Mackenzie, a Michigan State professor of veterinary pathology and study author, the killing is slow, letting the worms leave the eyes. Older drugs, he said, killed so fast that dead worm bodies worsened the blindness.

Ivermectin “is an extraordinarily safe drug,” Dr. Mackenzie added. “We’ve given out 25 million doses in Tanzania and had only two minor side effects.”

[McGill's Tim Geary, the director of the Institute of Parasitology at McGill University was Mackenzie’s primary research partner.

“We were questioning the way the drug worked and decided we wanted to look into it. This is a collaboration of 35 years. We were finally able to get together to do the research to answer that question.”…

Yovany Moreno, a graduate student at McGill, also was critical to the research breakthrough, Mackenzie said.]