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Progress Against River Blindness
| Article
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16327 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
3 / 1989 |
1,840 Words |
| Author
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Simon Jones
Simon Jones is a free-lance journalist writing on science and
medical topics. He lives in London. |
The African continent has been buffeted in recent years by a succession of natural and man-made catastrophes. Drought, starvation, and war have wreaked havoc on societies already imperiled by their relentless economic decline. Yet sometimes good news comes out of Africa. One such story concerns the remarkable progress being made in the fight against the parasitic disease onchocerciasis, or river blindness.
It would be hard to overstate the calamitous effects of onchocerciasis in areas where it is endemic. To date, some 20 million people suffer from the disease, and at least 1 million people have been blinded. By far the worst-hit area is sub-Saharan Africa. Here the parasite is found from the western coast right across the continent to Tanzania. The other major area of infection is central and South America: River blindness is a common ailment in regions of Guatemala, Venezuela, and Mexico.
Despite years of research, there is no known cure. Yet there are now two new developments that bring hope. The World Health Organization (WHO) is about to begin a program of mass treatment with ivermectin, a drug found to have remarkable results in treating the disease. And from London comes news of a test that promises to diagnose infection within weeks, rather than the current period of two years, a breakthrough that may be of immense help in the fight against river blindness.
The carrier of the disease is the female blackfly, Simulium damnosum. Infected larvae of the disease-causing worm, Onchocerca volvulus, pass into their human host when the blackfly takes a blood meal. Developing worms then wander through the tissues beneath the skin, finally settling down in groups of two or more. It takes about a year for each larva to develop into an adult worm, by which time it will be housed in a fibrous, tumor like mass, or nodule, varying in size from a few millimeters to several centimeters in diameter. These nodules are unsightly, but initially cause little distress.
Problems begin when the worms reproduce. New larvae, or microfilariae, begin to leave the nodules and migrate in millions throughout the body, especially in the skin. Here they are taken up by other biting blackflies, and the cycle continues. While live microfilariae cause little inflammation, the gradual buildup of dead and dying microfilariae, and the release of antigenic materials from them, causes persistent inflammation and itching, serious scarring, and permanent thickening of the skin. The disease has a general debilitating effect on its victims and may also have a
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