Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm Onchocerca volvulus. Symptoms include severe itching, bumps under the skin, and blindness. It is the second-most common cause of blindness due to infection, after trachoma.The parasite worm is spread by the bites of a black fly of the Simulium type. Usually, many bites are required before infection occurs. These flies live near rivers, hence the common name of the disease. Once inside a person, the worms create larvae that make their way out to the skin, where they can infect the next black fly that bites the person. There are a number of ways to make the diagnosis, including: placing a biopsy of the skin in normal saline and watching for the larva to come out; looking in the eye for larvae; and looking within the bumps under the skin for adult worms.A vaccine against the disease does not exist. Prevention is by avoiding being bitten by flies. This may include the use of insect repellent and proper clothing. Other efforts include those to decrease the fly population by spraying insecticides. Efforts to eradicate the disease by treating entire groups of people twice a year are ongoing in a number of areas of the world. Treatment of those infected is with the medication ivermectin every six to twelve months. This treatment kills the larvae but not the adult worms. The antibiotic doxycycline weakens the worms by killing an associated bacterium called Wolbachia, and is recommended by some as well.
These include hyperglucagonemia, zinc deficiency, fatty acid deficiency, hypoaminoacidemia, and liver disease. Mechanism
The pathogenesis is also unknown. Diagnosis
Histology
The histopathologic features of NME are nonspecific and include:
epidermal necrosis
subcorneal pustules
confluent parakeratosis, epidermal hyperplasia, and marked papillary dermal hyperplasia in a psoriasiform pattern
angioplasia of papillary dermis
suppurative folliculitisThe vacuolated, pale, swollen epidermal cells and necrosis of the superficial epidermis are most characteristic. Immunofluorescence is usually negative. Management
Managing the original condition, glucagonoma, by octreotide or surgery. After resection, the rash typically resolves within days. See also
List of cutaneous conditions

References


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