Scientists at Washington University School of Medicine in St. Louis have received nearly $2 million from the Bill & Melinda Gates Foundation to develop a new diagnostic test for “river blindness,” a neglected tropical disease.
Known formally as onchocerciasis, the disease afflicts some 37 million people in more than 30 countries, mostly in sub-Saharan Africa. River blindness is caused by a parasitic worm, Onchocerca volvulus, and is spread by the bites of black flies that breed in fast-flowing rivers, hence the name river blindness. While the disease can lead to blindness, it more commonly causes less severe visual impairment, disfiguring skin lesions and severe itching.
“River blindness remains a devastating illness for millions of people, most of whom live in poverty in Africa and Latin America,” said project leader Gary Weil, MD, an infectious diseases specialist at the School of Medicine. “We have most of the tools we need to eliminate this disease, but improved diagnostic methods are necessary to help steer the program.”
In recent years, the World Health Organization (WHO) has led a massive public health program to control onchocerciasis. Each year, medication to treat the infection and prevent new cases is distributed to more than 100 million people living in areas where the infection is endemic. Mass treatment with ivermectin (Mectizan, made and donated by Merck & Co.) sterilizes the adult worms for several months and kills the microscopic larvae that migrate to the skin and eyes.
World Health Organization
River blindness is caused by the parasitic worm O. volvulus, pictured, and is spread by the bites of black flies that breed in fast-flowing rivers. Adult worms can live in nodules under the skin for years and can be difficult to detect with current diagnostic tests.
Unfortunately, the current test used to diagnose onchocerciasis and evaluate the success of the WHO effort does not detect the presence of adult female worms. Adult worms can live in nodules under the skin for years. After the temporary effects of ivermectin wear off, the worms resume production of parasite larvae that are transmitted by flies and cause new cases of the disease.
“One challenge we face as we work to eradicate this disease is to accurately determine whether mass distribution of the medication has succeeded to the point where there is no risk that transmission of new cases will resume,” said Weil, who specializes in parasitology and immunology.
The current diagnostic test for onchocerciasis looks for parasite larvae in small skin biopsies, but is not a reliable marker for ongoing infection with adult worms.
Weil’s research group will search for biological “markers” that indicate the presence of living adult female worms in humans. They will look for excretion products or snippets of genetic material from the worms in blood and urine samples.
Weil will work with Reid Townsend, MD, PhD, professor of medicine, and Makedonka Mitreva, PhD, assistant professor of medicine and of genetics, to identify markers that are found exclusively in people infected with onchocerciasis, but not in those who are healthy or in people with infections caused by other parasitic worms.
Townsend brings to the project extensive expertise in proteomics (the identification of proteins in biological samples), and Mitreva is an authority on the analysis of DNA and genomes of nematode worms, including the parasitic worm that causes river blindness.
The first year of the project will focus on identifying the biomarkers. In the second year, the researchers will work toward developing a test that can easily and accurately detect the presence of onchocerciasis.
“We’re using a multidisciplinary approach to develop a new tool that will help the international effort to eradicate river blindness,” Weil said. “With recent advances in genomics and proteomics, we’re optimistic that we can accomplish this task. ”
Washington University School of Medicine
’s 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish
and St. Louis Children’s
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