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INTRODUCTION

KEY POINTS

  • Onchocerciasis is a chronic, disabling vector-borne disease caused by infestation with the filarial nematode worm Onchocerca volvulus that not only leads to physical and psychosocial sequelae, but also causes profound socioeconomic problems.

  • An estimated 37 million people are afflicted, especially in sub-Saharan Africa, with Nigeria accounting for about one-third of the world’s cases.

  • Clinical presentation reflects variations in a host’s immune response to the parasite.

  • The classic lesion is the onchocercoma, a firm, painless nodule that occurs in the subcutaneous tissue.

  • Most of the burden of the skin disease occurs as a result of severe, intolerable pruritus.

  • Mass treatment with ivermectin in affected communities has been highly successful in reducing the disease burden.

  • There remains a need for sustainability of control measures to maintain the gains in management of the disease.

Onchocerciasis (river blindness) is a vector-borne parasitic disease caused by the filarial nematode worm, Onchocerca volvulus. Infection is acquired through the bite of the insect vector, blackflies of the genus Simulium, which breed in fast-flowing streams and rivers. Members of the Simulium damnosum complex are the major vectors in Africa, whereas numerous other species are vectors of the disease in Latin America.1 People residing in rural areas near fast-flowing rivers and streams have the highest risk of acquiring onchocerciasis. Although the disease occurs in Yemen and in six countries in Central and South America, 99% of the disease occurs in 27 sub-Saharan African countries stretching between 15°N and 14°S, from Senegal in the west to Ethiopia in the east, where it causes blindness and skin disease.2

Onchocerciasis is a chronic, disabling disease that is a major public health problem and an even more profound socioeconomic problem that extends beyond the infected individual, affecting families, communities, and countries as a whole.1 It results in significant morbidity, psychosocial problems, and reduction in quality of life of those affected. Impaired social interaction, low morale, stigmatization, and the socioeconomic impact of the disease must be emphasized. The manifestations of the disease have resulted in abandonment of vast areas of fertile land and a poor attitude with regard to work. The disease has led to the collapse and desertion of families and vast communities and is one of the top five causes of blindness in the world, ranking second to trachoma as a cause of infectious blindness.3,4

Estimates indicate that 37 million individuals, mostly in tropical Africa, are infected.5,6 Nigeria accounts for about one-third of the world’s cases of onchocerciasis, and 60% of the cases occur in West Africa, with 18 to 20 million persons at risk of infection, 7.9 million affected, and 200,000 blind from the disease.7 O’Neill first reported the presence of filariae in cases of “craw-craw,” as onchocerciasis is called in West Africa, in 1875. The term Onchocerca is derived from the Greek word ogkos, meaning “swelling or mass,” ...

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