Study raises hopes of vaccine for river blindness

Waiting for ivermectin tablets in rural Uganda Copyright: WHO/APOC/TDR/Crump

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A study published this month has raised hopes of developing a vaccine against river blindness (onchocerciasis) — a major disease in West and Central Africa as well as parts of Latin America.

The researchers targeted Onchocerca ochengi, a parasitic worm closely related to Onchocerca volvulus — the parasite that causes river blindness in people.

O. ochengi causes skin lesions in cattle and is spread by the bites of the same black flies as O. volvulus.

Cattle injected with a modified and weakened form of O. ochengi larvae “developed very high levels of protection against infection,” says lead researcher Alexander Trees, from the University of Liverpool, United Kingdom.

Two years later, vaccinated cattle in their natural environment had far fewer parasitic worms than unvaccinated cattle.

The findings suggest that it could be possible to develop a vaccine that protects people against river blindness using a similar approach, though the scientists point out that more research is needed.

The current treatment for river blindness is the drug ivermectin, which kills larval parasites but not the adult worms. These can live for more than ten years.

“A vaccine is essentially needed to control river blindness because ivermectin lacks the power to provide a permanent cure,” says Swapan Jana, secretary of the Society for Social Pharmacology, an India-based non-governmental organisation involved in public health issues.

Some evidence suggests that resistance to ivermectin is developing in some parts of Africa.

Onchocerciasis has blinded about half a million people, according to the World Health Organization. The disease occurs in Brazil, Colombia, Ecuador, Guatemala, Mexico, Venezuela, Yemen and thirty countries in Africa.

The research was published earlier this month (11 April) in Proceedings of the National Academy of Sciences.

Link to abstract of paper in Proceedings of the National Academy of Sciences

Reference: Proceedings of the National Academy of Sciences 103, 5971 (2006)