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Researchers Develop Simple Test for River Blindness

  • Jessica Berman

Diagnosing the tropical parasitic illness Onchocerciasis, also known as river blindness, might soon be as easy as testing a urine sample. Such a simple test would permit more effective diagnosis and treatment of a disease that now afflicts nearly 18 million people around the world.

People call Onchocerciasis "river blindness" because it’s caused by the bite of a parasitic-worm-infected black fly that lives near rivers. The illness is most common in sub-Saharan Africa, although it also exists in parts of Yemen and in Central and South America.

The river blindness parasite has an active and inactive phase, making it difficult to treat the disease. During its active phase, the female worm produces millions of microscopic eggs that migrate to different tissues throughout the body. Infection of the eyes can lead to blindness.

The disease is usually treated with the antiparasitic agent Ivermectin, which lowers the number of eggs produced by the worm, and an antibiotic, doxycycline, which sterilizes it.

But according to Daniel Globisch, a researcher at Scripps Research Institute in California, it is difficult to determine when the worm is active. That information would help health care providers know whether their treatment is effective or not. It would also reduce the risk that wasteful use of antibiotics might promote drug resistance in the river blindness parasite.

Currently, Globisch says, the only way is to be certain that the worm is active is to do a skin biopsy to look for signs of the parasite.

“This is very invasive and also painful and really uncomfortable for the people. And that’s why a non-invasive diagnostic is as important,” Globisch said.

Globisch and colleagues think they found one. They have identified a single biomarker produced by the worm - a chemical that sends signals from one nerve cell to another - that is present in the patient's urine during the active phase.

“The single marker is linked to the worm’s lifecycle. And that is why we believe this is the perfect marker to get a test,” Globisch said.

Globisch says the test would be inexpensive and portable. Infected individuals also suffer severe itching and the Scripps scientists are investigating treatments to ease that symptom for as long as patients with river blindness harbor the parasite.

An article on a urine test for river blindness is published in the journal Proceedings of the National Academy of Sciences.