Neglected tropical diseases

WHO declares Ecuador free of onchocerciasis (river blindness)

29 September 2014 | Geneva


Ecuador has become the second country in the world after Colombia to be declared free of onchocerciasis (also known as river blindness) after successfully implementing elimination activities for decades.

“This is an important success story for Ecuador and for other countries that are working to eliminate onchocerciasis,” said Dr Carissa Etienne, Director of the Pan American Health Organization (PAHO). “It shows what can be accomplished when countries undertake the sustained action that is needed, with strong support from their governments and committed international partners.

Colombia was the first to be declared free in 2013. Elimination in both countries follow sustained large-scale treatment of at-risk populations with ivermectin.

Both Colombia and Ecuador interrupted transmission of the disease in 2007 and 2009 respectively. Mexico and Guatemala stopped transmission in 2011, with verification still to be done. All 13 foci in the Region of the Americas achieved coverage of more than 85% in 2006, and transmission was interrupted in 10 out 13 by the end of 2011.

Elimination of the disease in Ecuador posed a substantial challenge because the blackfly (Simulium exiguum) that transmits the parasite is a more efficient vector than Simulium spp., which is responsible for transmission of the disease in Africa.

The elimination of onchocerciasis is another step toward reducing poverty in Ecuador, and is a significant improvement in Ecuadorians' quality of life,” said Ecuador’s Minister of Health Carina Vance, speaking during the opening session of the 53rd PAHO Directing Council in Washington, D.C. “Ecuador will continue its fight to eliminate so-called diseases of poverty to achieve a good life for all.”

Ecuador’s program had a single endemic focus bordering the Cayapas, Santiago and Onzole rivers in the northern part of Esmeraldas Province. Ecuador’s Ministry of Health has distributed ivermectin in the country since 1990. In 2008, a combined 27 372 ivermectin treatments were administered to just over 16 000 people.

In 2010, treatment stopped after transmission of onchocerciasis in the country was successfully interrupted using a twice yearly community-wide administration of ivermectin, combined with health education programmes in affected areas – a strategy recommended by the Region.

An entomological evaluation conducted in 2012 at the end of a 3-year surveillance period showed that morbidity had been eliminated and transmission of the parasite remained interrupted.

Based on these results the Steering Committee of the Onchocerciasis Elimination Program for the Americas (OEPA) in consultation with Ecuador’s Ministry of Health in July 2013 requested WHO to formally verify elimination.

An International Verification Team visited Ecuador in May 2014 and, based on its recommendations, in September 2014, WHO’s Director-General Dr Margaret Chan issued an official letter confirming that Ecuador had achieved elimination of onchocerciasis.

Onchocerciasis in the Americas

The campaign to eliminate river blindness in the Americas began through the Onchocerciasis Elimination Program of the Americas (OEPA) in 1993 with the objective of eliminating ocular morbidity and transmission throughout the Americas by 2012.

In the late 1980s, an estimated 500 000 people in the Americas were at risk of onchocerciasis in six countries: Brazil, Colombia, Ecuador, Guatemala, Mexico and the Bolivarian Republic of Venezuela.

The donation of ivermectin by Merck stimulated new partnerships and opportunities to fight onchocerciasis.

In 1991, all PAHO Member States resolved to work towards elimination of onchocerciasis by adopting resolution CD35.R14. A new 2008 resolution (CD48.R12) sets the goal of interrupting onchocerciasis transmission by 2012.

This goal was ratified in 2009 to eliminating neglected diseases in resolution (CD49.R19).

The disease

Onchocerciasis – or “river blindness” – is a parasitic disease caused by the filarial worm Onchocerca volvulus transmitted by repeated bites of infected blackflies. These blackflies breed in fast-flowing rivers and streams, mostly in remote villages located near fertile land where people rely on agriculture.

In the human body, the adult worms produce embryonic larvae (microfilariae) that migrate to the skin, eyes and other organs. When a female blackfly bites an infected person during a blood meal, it also ingests microfilariae which develop further in the blackfly and are then transmitted to the next human host during subsequent bites.

Signs and symptoms

Onchocerciasis is an eye and skin disease.

Symptoms are caused by the microfilariae, which move around the human body in the subcutaneous tissue and induce intense inflammatory responses, especially when they die.

Infected people may show symptoms such as severe itching and various skin lesions. In most cases, nodules develop under the skin.

Some infected people develop eye lesions which can lead to visual impairment and permanent blindness.