Progress to help eliminate river blindness
22 July 2009 - Drug studies are showing that treatment for onchocerciasis, also known as river blindness, could help to eliminate this debilitating skin disease. River blindness affects 37 million people, mostly living in poor, rural African communities.
Transcript of the podcast
Jamie Guth: You’re listening to the WHO podcast, and my name is Jamie Guth. In this episode we discuss news on two different drugs that treat onchocerciasis, also known as river blindness, a disease that affects many in Africa.
Onchocerciasis causes a debilitating skin disease -- severe itching and disfigurement -- as well as blindness. Blackflies, which transmit the disease, deposit infective larvae in people's skin which then grow into worms. Over 37 million people are infected, often living in poor, rural African communities. Today two researchers from the WHO-based Special Programme for Research and Training in Tropical Diseases, known as TDR, tell us about important new studies that are helping to eliminate this disease. Dr Hans Remme has been leading a study on ivermectin, a drug that is given once a year to people to kill the larvae of the worms that cause the problems.
Dr Hans Remme: Since ivermectin kills the larvae, annual treatment over infected communities has been very effective in controlling the disease manifestations. Ivermectin is donated free of charge by the manufacturer, Merck and Co. and APOC, the African Programme for Onchocerciasis Control, has done a fantastic job in making sure that the drugs get every year to the people who need them using an innovative creative approach called community-directed treatment.
Over 60 million people are now receiving ivermectin treatment annually. However, the adult worms are not killed by ivermectin. After treatment they start producing new larvae again. This makes it necessary to repeat treatment at least annually, but we did not know how long this was needed, if the parasite could ever be eliminated with this approach, and if treatment ever could be stopped.
The Public Library of Science Journal on Neglected Tropical Diseases has now published a study that shows after 15 to 17 years treatment, in three areas in Mali and Senegal, we were able to stop treatment, without further transmission. Two years after the last treatment, there were no infected people and there were no infected blackflies. This is the first time we have had evidence of being able to eliminate onchocerciasis with ivermectin.
Jamie Guth: Does this mean that you can stop the treatment after 17 years everywhere in Africa?
Dr Hans Remme: Well, Africa is large, the study has established the principle of elimination, but we need more information to understand how this will play out in different parts of the continent.
Jamie Guth: How many countries in Africa have been giving out ivermectin for this 15 to 17 year time period? When will you know if it is possible to stop treatment elsewhere?
Dr Hans Remme: The study was done in special areas with the longest history of ivermectin treatment, that's why we selected them. In most countries treatment started only 10 years ago, and then only in part of the country. However after 10 years of treatment, one should be able to see infection levels are falling towards a clear end point.
Jamie Guth: Thank you, Dr Remme. Now we're going to talk to Dr Annette Kuesel, who is managing a clinical trial of a new drug for river blindness, called moxidectin. She has just come back from the newly created clinical trials centre in the northeast of the Democratic Republic of the Congo. Dr Kuesel, what is different about this drug?
Dr Annette Kuesel: Well, as you heard from Dr Remme, ivermectin is effective against the larvae, we think that moxidectin could actually work against the adult worms, either killing them or sterilizing them. If that is indeed the case, then moxidectin would maybe have to be given only 5 to 6 years as opposed to 10, 15 or 17 years. Especially for the countries that have only recently started to distribute ivermectin, in particular post conflict countries like Liberia or DRC, that would make a huge difference.
Jamie Guth: Where are these trials being conducted?
Dr Annette Kuesel: Well we are conducting trials in Ghana, Liberia and the Democratic Republic of Congo, in areas which for one reason or another have not had widespread ivermectin distribution yet. In Liberia and Democratic Republic of Congo this is the case because of the recent conflicts in these countries. Now you can imagine that working in post conflict countries and post conflict areas is actually very challenging and we have found that there is no research capacity there, so we had to actually build research centres from scratch in two sites and in one site in Rethy, Ituri, we were lucky we were given buildings that hadn’t been used since the war to renovate. Now building the capacity includes everything from generators, internet access, every single little machine that is needed to conduct the evaluations that are required by the study protocols.
Now one of the things that I find particularly satisfying in working in these areas is that on the one hand, drug development is a very risky business, only one out of five drugs on average that make it into this stage of development actually make it into the use they are being developed for. Now for us this means that our work will never be in vain, even if moxidectin turns out to not be the drug that we want it to be, the capacity that we built will remain there both the infrastructure and in particular also the personnel capacity.
Jamie Guth: So for moxidectin, when do you think you will know if it works?
Dr Annette Kuesel: We will have initial data coming out sometime in the first quarter of 2010, and then the results of the studies that we are just initiating in Liberia and we hope to initiate soon in Ghana and DRC will be available sometime in 2012.
Jamie Guth: If you would like to learn more about this subject, there are links to related information on the transcript page of this podcast episode. Look for the link to the podcast on the home page of our web site, at www.who.int
That's all for this episode of the WHO podcast. Thanks for listening. If you have any comments on our podcast or have any suggestions for future health topics do drop us a line. Our email address is Podcast@who.int.
For the World Health Organization, this is Jamie Guth in Geneva.