River Blindness Eliminated in Colombia

The World Health Organization (WHO) headquarters in Geneva, Switzerland, is an impressive compound, high in the hills overlooking Lake Geneva, with the brightness of international dress and the bustle of multiple languages throughout its halls. In the front is a bronze statue depicting a young boy holding a stick, and behind him, a blind man staring unseeingly at the headquarters (Figure 1). Seemingly heading into WHO seeking relief, the blind man is the embodiment of villages ravaged by onchocerciasis or ‘‘river blindness. ’’ It is fitting that such a statue grace the entrance to WHO, as it serves as a daily reminder of the scourge of avoidable blindness and the need to remain focused on this often frustrating disease. The control of onchocerciasis, with no vaccine to assist the effort, has been a long and sometimes discouraging venture. Onchocerciasis is a complicated disease. Its life cycle includes the bite of the black fly, which breeds in fast moving streams and rivers. An infected fly will bite humans and pass the third stage larvae into the host’s blood. The larvae then migrate and grow into adult worms inside nodules under the skin, but also occasionally along the aorta. The male and female worms mate inside these nodules. Female worms can release 700–1500 microfilariae per day. These microfilariae migrate with impunity throughout the host’s body, invading the cornea and interior of the eye. Dying microfilariae trigger an immune response that leads to intense itching, and over time to corneal opacity, uveitis, secondary glaucoma and retinal degeneration. In communities close to rivers where the fly breeds, up to 30% of young men were blind, and whole villages ultimately abandoned. Concerted efforts to combat onchocerciasis began in 1974 with the Onchocerciasis Control Program (OCP), sponsored by four United Nations agencies, and launched in 11 countries in West Africa. The focus of the program was aerial insecticide spraying to kill the larvae of the black fly (Figure 2). In 1987, with the generous donation program of Mectizan by Merck, the focus shifted to include community-wide distribution of ivermectin. In 1995, a second program to combat onchocerciasis, the African Programme for Onchocerciasis Control (APOC) was established to control onchocerciasis in 19 countries not covered by the OCP. The focus of APOC is community-directed treatment with ivermectin, and it is still ongoing. But Africa has not been the only site of onchocerciasis; 6 of the 38 endemic countries were in Central and South America. In 1991, a resolution of the Pan American Health Organization (PAHO) called for the elimination of onchocerciasis. This led to the establishment of the Oncherciasis Elimination Program for the Americas. This was a remarkable goal, as it called for elimination, not just control, of a major infectious disease. Specifically, elimination means the interruption of transmission; the parasite population is unable to recover, transmission stops, and treatments are halted. Formal declaration of control requires that the population be followed with at least 3 years of post treatment surveillance confirming the lack of transmission. When all onchocerciasis foci in a country have reached the elimination stage, an international team is called in under the auspices of WHO to verify the disease’s elimination. From 1993–2012, over 11 million ivermectin treatments were administered in the Americas. At this