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NIAID Discovery May Help Eliminate River Blindness

Public health officials in Africa and Latin America are working to eradicate onchocerciasis, commonly known as river blindness. The disease, which affects an estimated 37 million people worldwide, is caused by Onchocerca volvulus, a parasitic worm transmitted from person to person by the bite of infected blackflies. People with onchocerciasis can have itchy skin rashes and nodules under the skin. In severe cases, lesions develop in the eye that impair vision and may lead to blindness.

Although a treatment exists that kills the microfilariae (larval offspring) of O. volvulus, adult worms can remain alive in nodules that form under the skin for approximately 15 years. Because of the lifecycle of the worm, it usually takes a year before microfilariae can be detected in skin biopsies. As a result, people can unwittingly harbor the parasite and help spread it to others. Eliminating onchocerciasis in affected areas not only requires an effective treatment but also a rapid test that identifies infected people as early as possible.

A cross-section of an adult O. volvulus worm filled with many microfilariae.
A cross-section of an adult O. volvulus worm filled with many microfilariae. Credit: CDC

In the late 1980s, a research team led by Dr. Thomas Nutman in the NIAID Laboratory of Parasitic Diseases began searching for a better marker of onchocerciasis. He studies neglected tropical diseases to find ways to better prevent and treat them. He also works with people referred to the National Institutes of Health with infections caused by parasitic worms like O. volvulus. Although the parasite is not endemic to the United States, immigrants and people who travel to affected areas are vulnerable to infection.

"The gold-standard test is a skin snip that does not detect the worm until long after infection is initiated," said Dr. Nutman. "We wanted to develop a rapid, less-invasive diagnostic that could be used here and in the countries affected by the parasite."

In 1991, led by the efforts of Dr. Edgar Lobos, a postdoctoral fellow in Dr. Nutman's lab, the team identified OV-16, an immune-stimulating protein, or antigen, found in the parasite. The team used the marker to develop a simple test that could accurately detect antibodies to OV-16 in the blood. Antibodies to the worm could be detected within three months after infection. Dr. Nutman shared OV-16 with other labs that independently verified the marker's specificity for O. volvulus. Armed with the research evidence, NIAID patented OV-16 in hopes of partnering with a company that could develop and manufacture a diagnostic test for use in people.

In the late 1990s, an Australian company developed a prototype rapid diagnostic test based on OV-16. Although the test was promising in clinical studies, further development of the diagnostic stalled in the early 2000s. "Because there is not much, if any, profit in manufacturing something for a disease rampant in poor countries, companies sometimes let these projects go, which is what happened with OV-16," said Dr. Nutman.

Dr. Nutman continued to share OV-16 with the research community, but faced with little interest from potential commercial partners, NIAID eventually let the patent expire. In 2011, with increasing evidence that river blindness could be eradicated in Africa, there was renewed interest in a rapid point-of-care OV-16 test. PATH, a nonprofit global health organization, collaborated with Dr. Nutman's lab to develop a commercially viable OV-16 diagnostic. In October 2012, PATH identified a company, Standard Diagnostics, Inc., interested in manufacturing and distributing the test to countries in need.

"We are excited that the test, developed from a discovery made in NIAID labs, could be available within the next few years," says Dr. Nutman. "For people living in remote areas who may need to travel days or weeks to get tested, getting test results and the appropriate medicine within minutes will significantly improve their quality of life."

Last Updated November 27, 2012

Last Reviewed November 27, 2012