Infected . The worm responsible for river blindness can cause serious skin lesions.
WHO
A veterinary drug that kills the worms in cattle can also fight against river blindness, a debilitating infection parasite that affects 37 million people across the world, researchers say. But experts warn against the temptation of the compound in humans yet.
blind people contract rivers, also known as onchocerciasis, when bitten by black flies that carry a nematode known as volvulus Onchocerca . Worm larvae mature and mate, producing up to 1000 "microfillariae" offspring per day, which migrate to the surface of the skin and eyes. When microfillariae die, they cause itchy lesions that can lead to blindness. The disease often forces farmers to abandon the many lush river valleys with black flies infected for less fertile areas.
Doctors currently treat river blindness Ivermectin, a drug that kills the microfillariae and reduces the fertility of adult worms. Ivermectin has reduced cases of blindness and injuries in countries such as Senegal and Mali. But ivermectin does not target to nearly mature that cause new infections through the bite of a black fly. Instead, the drug control symptoms until the worms eventually die out. Scientists are still searching a compound that could block infection altogether, for example by killing the teenagers to arrival.
Researchers led by Kim Janda, a chemist at the Scripps Research Institute in San Diego, California, decided to focus on an enzyme called chitinase, which breaks down and rebuilds O. volvulus outer housing larvae during the final molt before adulthood. They screened 1,500 drugs, looking for one that blocked the enzyme. The best candidate turned out to be a veterinary drug known as closantel, which kills liver parasites in cattle. When Janda's team cultivated O almost mature. volvulus larvae in solutions that contained various amounts of the drug for 6 days, only 1.4% of closantel-dosed larvae had moulted against 60% in the control group, reports Team online this week in Proceedings of the national Academy of sciences .
If closantel has the same effect in humans, it could prevent infections begin, said Roger Prichard, parasitology at McGill University in Montreal, Canada. And because it works in a completely different way of ivermectin, he said, all strains of O. volvulus , which show resistance to ivermectin in the future could be treated with closantel.
Janda said he is optimistic about working with closantel as it has already proved safe in farm animals. "This moves the drug discovery process along more quickly."
But Prichard warns that the highway can not be so fast. Closantel is not approved for use in all animals in all countries, including the United States, he said. And it binds to a protein present in the blood, which might lead to side effects in humans. In addition, the team would have to prove that Janda Closantel lasts long enough to provide protection from intermittent doses; one of the reasons why ivermectin works so well is that it should be taken once or twice a year. "It is far from showing inhibition of the enzyme to actually have a drug," said Prichard. "There are significant barriers that must be overcome."
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