A blackfly — transmitter of river blindness

Flickr/Marco Gaiani

A drug normally used in animals will be tested for its ability to control river blindness transmission in clinical trials in the Democratic Republic of Congo (DRC), Ghana and Liberia.

The phase III trials, launched today (1 July) at the World Conference of Science Journalists in London, United Kingdom, will assess the effectiveness of moxidectin in preventing transmission of the worms which cause river blindness, or onchocerciasis — one of the leading infectious causes of blindness in Africa.

The trials will last for the next two and a half years and will be run by the WHO Special Programme for Research and Training in Tropical Diseases (WHO/TDR), and Wyeth Pharmaceuticals, the company behind the drug. Fifteen hundred people at four sites in the three co­untries will be involved.

River blindness is a parasitic disease caused by Onchocerca volvulus worms transmitted from person to person by blackflies. More than 100 million people are at risk in 30 African countries and a few small areas in the Americas and Yemen.

Adult worms can live in the body for up to 15 years, producing millions of larval worms that migrate through the skin and eyes — causing blindness.

Currently the disease is treated with the drug ivermectin, which kills only the larvae so annual treatments for the worm's 15-year life cycle are required to ensure disease control.

Earlier trials have shown that as well as killing larvae moxidectin sterilises or kills adult worms, meaning it could interrupt the disease transmission cycle much earlier.

Didier Bakajika, a medical doctor with the On­chocerciasis Control Programme in the DRC and principal investigator of the trials, says initial phases proved the drug is safe despite its main use as an animal drug.

"No major adverse effects have been reported in the previous studies [with moxidectin] on humans," Bakajika told SciDev.Net. "Even the current standard treatment drug for river blindness [ivermectin] was initially a veterinary drug."

WHO/TDR has been working with African investigators and institutions in the three countries since 2007 to ensure existing or new centres are capable of conducting the trials, and the hope is that this capacity building will enable further trials.

But Bakajika says that war-torn DRC is a challenging place in which to work, with problems maintaining equipment and poor road links to equipment experts in major towns.

He adds that poor infrastructure could interfere with delivery of supplies, and Internet and telephone access.