Another tiny worm, another devastating disease. The worm this time is Onchocerca volvulus, which can be found inside infected blackflies. The disease is passed to a person after being bitten by a blackfly. Known as onchocerciasis, or river blindness, the symptoms range from skin rash, eye lesions that cause blindness and bumps under the skin. Onchocerciasis used to be a main cause of preventable blindness and skin disease, but thanks to efforts by the World Health Organization (WHO), this has changed.