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 wormsto 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. 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.
Current diagnostic methods include the painful cutting of "skin snips" from patients for microscopic analysis and an ELISA antibody test for microfilariae, which may yield positive results even for non-active infections. Health agencies need better diagnostic methods to track the progress of Onchocerciasis treatment campaigns and to wisely monitor the use of ivermectin and doxycycline to reduce the risk of resistance.
Janda envisions the new diagnostic test, which he hopes to develop over the next two years, as a simple, accurate and painless urine dipstick test, much like a home pregnancy test. The diagnostic would indicate the amount of the O. volvulus biomarker present in the sample to guide treatment decisions and assist global health leaders in their quest to eradicate the disease.
|Contact: Mika Ono|
Scripps Research Institute