Drug kills parasitic worm at its source

MICHIGAN STATE (US) — Scientists have unlocked how an anti-parasitic drug kills worms brought on by diseases like river  blindness and elephantitis.

Understanding how the drug ivermectin works has the potential to lead to new treatments for the diseases that afflict about 140 million people worldwide, mostly in equatorial Africa.

“Ivermectin is one of the most important veterinary and human anti-parasitic agents ever,” says Charles Mackenzie, professor of veterinary pathology at Michigan State University.

“Knowing specifically how it interacts with the body’s own immune system and kills parasitic worms opens up whole new treatment avenues.”

The research appears in the current edition of the Proceedings of the National Academy of Sciences.

Elephantiasis (lymphatic filariasis) is caused by tiny worms spread via mosquitoes and results in severe swelling of the legs, arms, and torso. River blindness (onchocerciasis) is spread by black flies, and after the worms die in a person’s eye, they can cause blindness and debilitating skin disease.

Ivermectin works by killing the first stage of the worm in the human body, and also appears to paralyze the reproductive tract of the adult female worms, stopping reproduction of new parasites.

What the researchers discovered is that the drug does this by preventing the worm from secreting proteins through a pore in its mid-body.

Ivermectin binds to receptors at the pore and blocks the secretions that normally block a person’s ability to attack and kill the worm. After the drug prevents them, the host’s own immune system is able to attack and kill the parasites.

“Understanding how the worms were avoiding the host’s immune responses will greatly enhance our ability to manipulate the immune system to the advantage of the host, and perhaps develop vaccines,” Mackenzie says.

“Also, one of the most important challenges in the overall effort against filarial infections relates to the development of resistance and the loss of efficacy of the drugs we use; this new knowledge provides an important key to understanding and perhaps preventing resistance.”

Researchers from McGill University contributed to the study.

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