A grading system has been developed to categorize the degree of skin involvement:
Acute papular onchodermatitis – scattered pruritic papules
Chronic papular onchodermatitis – larger papules, resulting in hyperpigmentation
Lichenified onchodermatitis – hyperpigmented papules and plaques, with edema, lymphadenopathy, pruritus and common secondary bacterial infections
Skin atrophy – loss of elasticity, the skin resembles tissue paper, lizard skin appearance
Depigmentation – leopard skin appearance, usually on anterior lower leg
Glaucoma effect – eyes malfunction, begin to see shadows or nothingOcular involvement provides the common name associated with onchocerciasis, river blindness, and may involve any part of the eye from conjunctiva and cornea to uvea and posterior segment, including the retina and optic nerve. The microfilariae migrate to the surface of the cornea. Punctate keratitis occurs in the infected area. This clears up as the inflammation subsides. However, if the infection is chronic, sclerosing keratitis can occur, making the affected area become opaque. Over time, the entire cornea may become opaque, thus leading to blindness. Some evidence suggests the effect on the cornea is caused by an immune response to bacteria present in the worms.The infected persons skin is itchy, with severe rashes permanently damaging patches of skin. Mazzotti reaction
The Mazzotti reaction, first described in 1948, is a symptom complex seen in patients after undergoing treatment of onchocerciasis with the medication diethylcarbamazine (DEC). Mazzotti reactions can be life-threatening, and are characterized by fever, urticaria, swollen and tender lymph nodes, tachycardia, hypotension, arthralgias, oedema, and abdominal pain that occur within seven days of treatment of microfilariasis.
Moxidectin
Moxidectin was approved for onchocerciasis in 2018 for people over the age of 11 in the United States. The safety of multiple doses is unclear. Epidemiology
About 21 million people were infected with this parasite in 2017; about 1.2 million of those had vision loss. As of 2017, about 99% of onchocerciasis cases occurred in Africa. Onchocerciasis is currently relatively common in 31 African countries, Yemen, and isolated regions of South America. Over 85 million people live in endemic areas, and half of these reside in Nigeria. Another 120 million people are at risk for contracting the disease. Due to the vectors breeding habitat, the disease is more severe along the major rivers in the northern and central areas of the continent, and severity declines in villages farther from rivers. Onchocerciasis was eliminated in the northern focus in Chiapas, Mexico, and the focus in Oaxaca, Mexico, where Onchocerca volvulus existed, was determined, after several years of treatment with ivermectin, as free of the transmission of the parasite.According to a 2002 WHO report, onchocerciasis has not caused a single death, but its global burden is 987,000 disability adjusted life years (DALYs). The severe pruritus alone accounts for 60% of the DALYs. Infection reduces the hosts immunity and resistance to other diseases, which results in an estimated reduction in life expectancy of 13 years. History
Onchocerca originated in Africa and was exported to the Americas by the slave trade, as part of the Columbian exchange that introduced other old world diseases such as yellow fever into the New World.