StemCell Therapy

Onchocerciasis ( or ), also known as river blindness and Robles disease, is a disease caused by infection with the parasitic worm Onchocerca volvulus.[1] Symptoms include severe itching, bumps under the skin, and blindness.[1] It is the second most common cause of blindness due to infection, after trachoma.[2]

The parasite worm is spread by the bites of a black fly of the Simulium type.[1] Usually many bites are required before infection occurs.[3] These flies live near rivers therefore the name of the disease.[2] Once inside a person the worms create larvae that make their way out to the skin.[1] Here they can infect the next black fly that bites the person.[1] 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.[4]

A vaccine against the disease does not exist.[1] Prevention is by avoiding being bitten by flies.[5] This may include the use of insect repellent and proper clothing.[5] Other efforts include those to decrease the fly population by spraying insecticides.[1] Efforts to eradicate the disease by treating entire groups of people twice a year is ongoing in a number of areas of the world.[1] Treatment of those infected is with the medication ivermectin every six to twelve months.[1][6] This treatment kills the larva but not the adult worms.[7] The medication doxycycline, which kills an associated bacterium called Wolbachia, appears to weaken the worms and is recommended by some as well.[7] Removal of the lumps under the skin by surgery may also be done.[6]

About 17 to 25 million people are infected with river blindness, with approximately 0.8 million having some amount of loss of vision.[3][7] Most infections occur in sub-Saharan Africa, although cases have also been reported in Yemen and isolated areas of Central and South America.[1] In 1915, the physician Rodolfo Robles first linked the worm to eye disease.[8] It is listed by the World Health Organization as a neglected tropical disease.[9]

Adult worms remain in subcutaneous nodules, limiting access to the host's immune system.[citation needed] Microfilariae, in contrast, are able to induce intense inflammatory responses, especially upon their death. Wolbachia species have been found to be endosymbionts of O. volvulus adults and microfilariae, and are thought to be the driving force behind most of O. volvulus morbidity. Dying microfilariae have been recently discovered to release Wolbachia surface protein that activates TLR2 and TLR4, triggering innate immune responses and producing the inflammation and its associated morbidity.[10] The severity of illness is directly proportional to the number of infected microfilariae and the power of the resultant inflammatory response.[citation needed]

Skin involvement typically consists of intense itching, swelling, and inflammation.[11] A grading system has been developed to categorize the degree of skin involvement:[12][13][verification needed]

Ocular 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.[11] 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.[citation needed] The skin is itchy, with severe rashes permanently damaging patches of skin.

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.

The phenomenon is so common when DEC is used that this drug is the basis of a skin patch test used to confirm that diagnosis. The drug patch is placed on the skin, and if the patient is infected with O. volvulus microfilaria, localized pruritus and urticaria are seen at the application site.[14]

This is an unusual form of epidemic epilepsy associated with onchocerciasis.[15] This syndrome was first described in Tanzania by Louise Jilek-Aall, a Norwegian psychiatric doctor in Tanzanian practice, during the 1960s. It occurs most commonly in Uganda and South Sudan.

See the article here:
Onchocerciasis - Wikipedia, the free encyclopedia

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