Neglected tropical diseases

WHO revises onchocerciasis guidelines as countries approach elimination targets


22 January 2016 | Geneva −− The World Health Organization (WHO) targets the elimination of onchocerciasis (river blindness) in Latin America, in selected African countries and in Yemen by 2020 as highlighted in the WHO Roadmap on neglected tropical diseases (NTDs). As countries approach the end of the treatment phase, WHO has published revised guidelines incorporating new evidence gathered during the past 15 years.

These evidence-based guidelines come at a time when countries are making steady progress and moving towards elimination targets” says Dr Dirk Engels, Director of the Department of Control of Neglected Tropical Diseases. “They provide recommendations on when to stop large-scale treatment programmes and conduct post-treatment surveillance activities for a minimum period of 3 years before confirming the interruption of transmission and hence its elimination. The guidelines also include steps to undertake the process of verification of elimination of transmission.

WHO published its last onchocerciasis guidelines in 2001. Since then, the Onchocerciasis Elimination Program for the Americas (OEPA) has interrupted transmission in most foci. With sustained progress, WHO estimates that 12 countries in Africa (Benin, Burundi, Chad, Kenya, Mali, Guinea-Bissau, Guinea, Malawi, Niger, Senegal, Sierra Leone and Togo) will have eliminated the disease by 2020.

Following the closure of the African Programme for Onchocerciasis Control (APOC) on 31 December 2015, a new entity – the Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN) – which will be launched in May 2016,will promote an integrated approach to tackling onchocerciasis, along with four other high-burden neglected tropical diseases, including lymphatic filariasis, trachoma, schistosomiasis and soil-transmitted helminthiases.

WHO is facilitating the launch of an elimination programme in Yemen (where onchocerciasis in endemic) in collaboration with the Ministry of Health and Population, the World Bank and other international partners.

Progress

The shift from control to elimination of the disease comes after years of progress in affected countries in Africa – first through the pioneering efforts of the OCP in West Africa (1974–2002) and subsequently through the community-directed treatment programme of APOC (1995–2015).

In 2014 alone, more than 112 million people were treated in 22 countries in the African Region, representing 65% global coverage against onchocerciasis. A further 34 million were reached with additional health interventions using the network of trained health workers.

In Latin America, WHO has verified three countries – Colombia, Ecuador and Mexico – as free of the disease. An international team will visit a fourth country – Guatemala – in mid-2016 to verify the elimination of transmission.

There is a broad international commitment towards eliminating river blindness” says Dr Gautam Biswas, Coordinator of the Preventive Chemotherapy and Transmission Control unit. “An integrated approach to tackling onchocerciasis and lymphatic filariasis, which coexists in many countries in the African continent, will be a cost–effective approach benefitting entire affected populations.

The disease

Human onchocerciasis – also known as river blindness – is a parasitic disease caused by the filarial worm Onchocerca volvulus. The infection is transmitted by blackflies (Simulium spp.) that breed in fast-flowing rivers and streams, mostly in remote villages located near fertile land where people rely on agriculture.

Onchocerciasis is a disease of the eye and skin. Symptoms are provoked by the death of baby worms (microfilariae) that circulate in the subcutaneous tissue and in the eyes, inducing intense inflammatory responses. Infected people may show symptoms such as severe itching and various skin and eye lesions.

WHO recommends annual treatment with ivermectin for at least 10–15 years. Priority for semi-annual treatment is indicated where epidemiological data are not on track to achieve elimination by the target date. More than 99% of infected people live in 31 countries in sub-Saharan Africa. Onchocerciasis is also found in Yemen and in some countries of Latin America including Brazil and Guatemala.