River blindness, a devastating tropical disease that affects 18 million people in Africa, the Arabian peninsula, and Latin America, is caused by parasitic worms that burrow into the skin and release millions of tiny offspring that spread throughout the body. But, the worms themselves probably aren't the main culprits behind the disease, says an international team of scientists.

Instead, it's the worms' cargo of Wolbachia bacteria that provokes the body's severe inflammatory response, leading to blindness and serious skin disorders, the researchers report in the 8 March issue of the journal Science, published by the American Association for the Advancement of Science.

Pinpointing bacteria as the direct factor behind the disease's virulence may suggest new therapies for combating river blindness, especially since recent studies in infected humans have shown that the bacteria can be killed by the common antibiotic doxycycline.

River blindness is the second leading infectious cause of blindness in the world. It is spread to humans by the bite of black flies infected with the parasitic worm Onchocerca volvulus. The battle against river blindness is taking place on two fronts at the moment, with programs to control the spread of the black fly and to freely distribute an anti-worm medicine called ivermectin.

Onchocerca larvae deposited by the fly's bite burrow into the skin, where they mature and eventually send out tiny offspring called microfilariae that can migrate through the skin to the eye. When the microfilariae die, they trigger a severe immune response, resulting in eye inflammation and eventual
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Contact: Lisa Onaga
lonaga@aaas.org
202-326-7088
American Association for the Advancement of Science
7-Mar-2002