River blindness (onchocerciasis) and other ocular (eye) parasitic diseases that involve the retina affect people in many countries around the world.
Systemic symptoms (throughout the body):
- Itching (localized, then spreading to the whole body)
- Skin nodules
- Enlarged groin
- Skin pigmentary (color) changes
- Itching of the eyes
- Light sensitivity
- Inflammation within the eye
River blindness is transmitted to humans through the blackfly that lives along fertile riverbanks. Once a person is infected, the parasite migrates to all internal tissue of the eye except the lens, causing eye inflammation, bleeding, and other complications that lead to blindness.
Onchocerciasis is a major cause of blindness in 30 African nations—mainly in Western and Central Africa—as well as in Yemen and 6 countries in Latin America.
According to the US Centers for Disease Control and Prevention, the incidence of onchocerciasis is second only to trachoma,  leaving 18 million to 40 million people  around the world suffering from the disease.
River blindness can be diagnosed via skin biopsies called snips. Skin snips are put into saline (salt water), and if larvae (parasite eggs) exist, they will emerge from the snips. In addition, blood can be drawn to look for antibodies for the parasite; however, this technique is not widely available throughout the United States.
Treatment and prognosis
If diagnostic tests find that you are suffering from river blindness, your doctor will recommend a treatment of the anti-parasitic drug Ivermectin. 
Ivermectin will kill larvae (eggs), but the treatment does not kill adult worms. This means that as long as adult worms are present in your system, you must take doses of Ivermectin every 6 months. Once all signs of worms have cleared up, your doctor will take you off your prescription.