Onchocerca volvulus
O. vovulus, the causative agent of river blindness.
Scientific classification
Kingdom: Animalia Phylum: Nematoda Class: Secernentea Order: Spirurida Family: Filariidae Genus: Onchocerca Species: O. volvulus
Binomial name
Onchocerca volvulus Bickel 1982

Onchocerciasis (pronounced [ɒn.kəʊ.sɜːˈkaɪə.sɪs]) or river blindness is the world's second leading infectious cause of blindness. It is caused by Onchocerca volvulus, a parasitic worm that can live for up to fourteen years in the human body. The International Statistical Classification of Diseases and Related Health Problems (commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following codes are used with International Statistical Classification of Diseases and Related Health Problems. ... The International Statistical Classification of Diseases and Related Health Problems (commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... Image File history File links Size of this preview: 800 × 538 pixel Image in higher resolution (2083 × 1401 pixel, file size: 985 KB, MIME type: image/jpeg)Photomicrograph (glycerine mount) of the microfilarial pathogen Onchocerca volvulus in its larval form. ... Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... Animalia redirects here. ... Classes Adenophora    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms (Phylum Nematoda) are one of the most common phyla of animals, with over 20,000 different described species. ... This article needs to be wikified. ... In biology, binomial nomenclature is the formal method of naming species. ... Infection is also the title of an episode of the television series Babylon 5; see Infection (Babylon 5). ... Blindness is the condition of lacking visual perception due to physiological or psychological factors. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ... Earthworm A worm is an elongated soft-bodied invertebrate animal. ...

Life cycle

The life cycle of O. volvulus (Illustration: Giovanni Maki)

The life cycle of O. volvulus begins when a parasitised female Black fly of the genus Simulium takes a blood meal. Saliva containing stage three O. volvulus larvae passes into the blood of the host. From here the larvae migrate to the subcutaneous tissue where they form nodules and then mature into adult worms over a period of six to twelve months. After maturation, the smaller adult males migrate from nodules to subcutaneous tissue where they mate with the larger adult females, producing between 1000 and 3000 eggs per day. The normal adult worm lifespan is up to 15 years. The eggs mature internally to form stage one microfilariae, which are released from the female's body one at a time and remain in the subcutaneous tissue. Image File history File links Size of this preview: 579 × 599 pixel Image in higher resolution (2096 × 2169 pixel, file size: 391 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 579 × 599 pixel Image in higher resolution (2096 × 2169 pixel, file size: 391 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Subfamilies Parasimuliinae Simuliinae Genera Araucnephia Araucnephioides Archicnephia Austrosimulium Baisomyia Cnephia Cnesia Cnesiamima Crozetia Ectemnia Gigantodax Greniera Gydarina Gymnopais Kovalevimyia Levitinia Lutzsimulium Mayacnephia Metacnephia Paracnephia Parasimulium Paraustrosimulium Pedrowygomyia Prosimulium Simuliites Simulimima Simulium Stegopterna Sulcicnephia Tlalocomyia Twinnia A black fly (sometimes called a buffalo gnat or turkey gnat) is any member of... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Saliva is the watery and usually somewhat frothy substance produced in the mouths of humans and some animals. ... A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... The subcutis is the layer of tissue directly underlying the cutis. ... Look up Month in Wiktionary, the free dictionary. ... In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ...

These stage one microfilariae are taken up by black flies upon a blood meal, in which they mature over the course of one to three weeks to stage three larvae, thereby completing the life cycle. Humans are the only definitive host for O. Volvulus. The normal microfilariae lifespan is 1-2 years.

Causes of morbidity

Adult worms remain in subcutaneous nodules, limiting access to the host's immune system. Microfilariae, in contrast, are able to induce intense inflammatory responses, especially upon their death. Dying microfilariae have been recently discovered to release Wolbachia-derived antigens, triggering innate immune responses and producing the inflammation and its associated morbidity. 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. Severity of illness is directly proportional to the number of microfilariae and the power of the resultant inflammatory response. Wolbachia is a type of bacteria that infects arthropod species, including a high proportion of all insects. ... Wolbachia is a type of bacteria that infects arthropod species, including a high proportion of all insects. ... An endosymbiont (also known as intracellular symbiont) is any organism that lives within cells of another organism, i. ...

Skin involvement typically consists of intense itching, swelling, and inflammation. A grading system has developed to categorize the degree of skin involvement: Acute papular dermatitis - scattered pruritic papules; Chronic papular dermatitis - larger papules, resulting in hyperpigmentation; Lichenified dermatitis - hyperpigmented papules and plaques, with edema, lymphadenopathy, pruritus and common secondary bacterial infections; Skin atrophy - loss of elasticity, skin resembles tissue paper, 'lizard skin' appearance; Depigmentation - 'leopard skin' appearance, usually on anterior lower leg. Dermatitis is a blanket term literally meaning inflammation of the skin. It is usually used to refer to eczema, which is also known as Dermatitis eczema. ... A papule is a small, solid and usually conical elevation of the skin. ... Dermatitis is a blanket term literally meaning inflammation of the skin. It is usually used to refer to eczema, which is also known as Dermatitis eczema. ... A papule is a small, solid and usually conical elevation of the skin. ... Dermatitis is a blanket term literally meaning inflammation of the skin. It is usually used to refer to eczema, which is also known as Dermatitis eczema. ... A papule is a small, solid and usually conical elevation of the skin. ... The word plaque or placque may mean: Look up plaque and placque in Wiktionary, the free dictionary. ... Edema (American English) or oedema (British English), formerly known as dropsy or hydropsy, is swelling of any organ or tissue due to accumulation of excess lymph fluid, without an increase of the number of cells in the affected tissue. ... Lymphadenopathy is swelling of one or more lymph nodes. ...

Ocular involvement provides the common name associated with onchocerciasis, river blindness. The surface of the cornea is another area to which the microfilariae migrate, where they are also attacked by the immune system. In the area that is damaged, punctate keratitis occurs, which 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. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... A substance or object that is opaque is neither transparent nor translucent. ...

Treatment and control

The treatment for onchocerciasis is ivermectin (mectizan); infected people can be treated once every twelve months. The drug paralyses the microfilariae and prevents them from causing itching. In addition, while the drug does not kill the adult worm, it does prevent them from producing additional offspring. The drug therefore prevents both morbidity and transmission. Ivermectin is an anti-parasite medication and is effective against most common intestinal worms (except tapeworms), most mites, and some lice. ...

Since 1988, ivermectin has been provided free of charge by Merck & Co. through the Mectizan Donation Program (MDP). The MDP works together with ministries of health and non-governmental development organisations such as the World Health Organization to provide free Mectizan to those who need it in endemic areas. 1988 (MCMLXXXVIII) was a leap year starting on Friday of the Gregorian calendar. ... It has been suggested that Rosetta Biosoftware be merged into this article or section. ... The World Health Organization (WHO) is a specialized agency of the United Nations that acts as a coordinating authority on international public health, headquartered in Geneva, Switzerland. ... In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. ...

There are various control programs that aim to stop onchocerciasis from being a public health problem. The first was the Onchocerciasis Control Programme (OCP), which was launched in 1974 and at its peak covered 30 million people in eleven countries. Through the use of larvicide spraying of fast flowing rivers to control black fly populations and, from 1988 onwards, the use of ivermectin to treat infected people, the OCP eliminated onchocerciasis as a public health problem. The OCP, a joint effort of the World Health Organisation, the World Bank, the United Nations Development Programme and the UN Food and Agriculture Organization, was considered to be a success and came to an end in 2002. Continued monitoring ensures that onchocerciasis cannot reinvade the area of the OCP. 1974 (MCMLXXIV) was a common year starting on Tuesday. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... 1988 (MCMLXXXVIII) was a leap year starting on Friday of the Gregorian calendar. ... Logo of the World Bank The International Bank for Reconstruction and Development (IBRD, in Romance languages: BIRD), better known as the World Bank, is an international organization whose original mission was to finance the reconstruction of nations devastated by WWII. Now, its mission has expanded to fight poverty by means... The United Nations Development Programe (UNDP), the United Nations global development network, is the largest multilateral source of development assistance in the world. ... The Food and Agriculture Organization (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger. ... For album titles with the same name, see 2002 (album). ...

In 1992 the Onchocerciasis Elimination Programme for the Americas (OEPA) was launched. The OEPA also relies on ivermectin. 1992 (MCMXCII) was a leap year starting on Wednesday. ...

In 1995 the African Programme for Onchocerciasis Control (APOC) began covering another nineteen countries and mainly relying upon the use of ivermectin. Its goal is to set up a community-directed supply of ivermectin for those who are infected. In these ways, transmission has declined. 1995 (MCMXCV) was a common year starting on Sunday of the Gregorian calendar. ...

See also

• Carter Center River Blindness Program

CDC Parasites of Public Health Concern [1] The Jimmy Carter Presidential Library The Carter Center is a human rights organization, founded in 1982 and chaired by former U.S. President Jimmy Carter. ...

External links

• Mectizan Donation Program

 SHERMAN