LA JOLLA, Calif., Feb. 27, 2013 /PRNewswire-USNewswire/ -- Scientists at The Scripps Research Institute (TSRI) have found a telltale molecular marker for Onchocerciasis or "river blindness," a parasitic infection that affects tens of millions of people in Africa, Latin America and other tropical regions. The newly discovered biomarker, detectable in patients' urine, is secreted by Onchocerca volvulus worms during an active infection. The biomarker could form the basis of a portable, field-ready test with significant advantages over current diagnostic methods. "There has been a need for an inexpensive, non-invasive test that can discriminate between active and non-active river blindness infections during treatment campaigns," said Kim D. Janda, who is Professor and Ely R. Callaway, Jr. Chair in Chemistry, member of the Skaggs Institute for Chemical Biology, and director of the Worm Institute of Research and Medicine at TSRI. "We think that this new biomarker can be the basis for such a test." The work is described this week in an online Early Edition of the Proceedings of the National Academy of Sciences. Leading Cause of Vision Loss A leading cause of vision loss, Onchocerciasis infections are transmitted among humans by river-dwelling blackflies in tropical regions. The vast majority of cases occur in sub-Saharan Africa, although pockets of endemic infection exist in Yemen and in Central and South America. The major symptoms of the disease, including blindness, result from the spread of O. volvulus "microfilariae"—early-stage larval worms—to the eyes and other tissues, where they trigger damaging inflammatory reactions. Mass treatment campaigns, begun in the 1990s, have used the anti-worm drug ivermectin, as well as the antibiotic doxycycline, which kills a symbiotic bacterium within the worms. The World Health Organization's African Programme for Onchocerciasis Control has set a target date of 2025 for the eradication of the disease in that region. But Onchocerciasis treatment is seldom effective immediately, and often spares adult worms. The latter can remain in protected nodules under the skin of a patient and secrete microfilaria for a decade or more. Health agencies need better diagnostic methods not only to monitor the progress of Onchocerciasis treatment campaigns, but also to limit the use of ivermectin and doxycycline to reduce the risk of resistance.