AFRICA: One step nearer to cure for river blindness
NAIROBI, 12 March 2002 (IRIN) - It is bacteria inside parasitic worms, and not the worms themselves, that cause river blindness, according to the latest research published by British-based Nature magazine.
Onchocerciasis, more commonly known as river blindness, earned its name because of its most extreme manifestation. Its variety of symptoms range from serious visual impairment, including blindness; rashes, lesions, intense itching and de-pigmentation of the skin; lymphadenitis, which results in hanging groins and elephantiasis of the genitals; and general debilitation.
The World Health Organisation reports that of the 36 countries where the disease is endemic, 30 are in sub-Saharan Africa (plus Yemen) and six in South America. An estimated 17 to 18 million people suffer from it.
The minute offspring of parasitic worms - carried by black flies endemic in fertile riverside areas - called microfilaria were believed to cause the disease, Nature reported, with fragments of dead microfilaria prompting the human immune system to overreact.
Working with a genetically modified mouse mimic of human river blindness, however, Eric Pearlman of Case Western Reserve University in Cleveland, Ohio, has discovered that wolbachia microbes within the parasitic worms are probably the culprits.
Pearlman's team of researchers have found that bacteria-free worm extract did not cause severe disease in the test mice, but wolbachia-laden worms did. Furthermore, the researchers found a molecular receptor in the eye that is particularly sensitive to wolbachia, according to Nature. This receptor is crucial to eliciting an inflammatory immune response, which can lead to a cataract-like blindness occurring in humans.
Nature said these findings could lead to better ways of preventing or treating the disease.
"It's a very significant finding - it gives us a more precise idea of what's happening," the magazine quotes Alexander Trees of the Liverpool School of Tropical Medicine in England as saying. Moreover, Trees's researchers recently found that the parasitic worms need wolbachia bacteria to enable them to reproduce, and that antibiotics to kill wolbachia can therefore also serve to sterilise adult worms.
River blindness is currently managed by using chemicals to stop adult worms from reproducing, and with insecticides to kill the black flies that carry the worms. Nature reports that, based on the new findings regarding wolbachia's interaction with the human immune system, it may now be possible to use vaccines or other drugs to quell the disease itself, rather than focusing on the worms or flies.