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- Onchocerciasis is caused by filarial worm Onchocerca volvulus.
- Epidemiology: world’s second-leading cause of blindness.
- Approximately 18 million people are infected, and nearly one million have been permanently blinded or suffer severe visual impairment.
- 99% of onchocerciasis cases occur in Africa.
- O. volvulus transmitted to humans by blackflies (Simulium damnosum), which breed in fast-flowing rivers and streams.
- Disease is endemic in 31 countries in sub-Saharan Africa, plus Venezuela, Brazil, and Yemen; WHO has recently certified Columbia (2013), Ecuador (2014), Mexico (2015), and Guatamala (2016) to be free of human onchocerciasis.