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Onchocerciasis 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. Infection is also the title of an episode of the television series Babylon 5; see Infection (Babylon 5). ...
Blindness can be defined physiologically as the condition of lacking sight. ...
A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. ...
A worm is an elongated soft-bodied invertebrate animal. ...
Life cycle 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 one to three months. After the worms have matured they mate, the female worm producing between 1000 and 1900 eggs per day. The eggs mature internally to form stage one microfilariae, which are released from the female's body one at a time. Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ...
For the band, see Saliva (band). ...
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. ...
In Egyptian mythology, Month is an alternate spelling for Menthu. ...
An average Whooping Crane egg is 102 mm long, and weighs 208 grams A baby tortoise emerges from a reptile egg. ...
The microfilariae migrate from the location of the nodule to the skin where they wait to be taken up by a black fly. Once in the black fly they moult twice within seven days and then move to its mouthparts to be retransmitted. Model of the layers of human skin In zootomy and dermatology, skin is an organ of the integumentary system; which is composed of a layer of tissues that protect underlying muscles and organs. ...
In birds, moulting or molting is the routine shedding of old feathers. ...
Causes of morbidity When the microfilariae migrate to the skin they are a target for the immune system. White blood cells release various cytokines that have the effect of damaging the surrounding tissue and causing inflammation. This kills the microfilariae but is the cause of the morbidity associated with this disease. The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ...
White blood cells (also called leukocytes or immune cells) are a component of blood. ...
Cytokines are small protein molecules that are the core of communication between immune system cells, and even between these cells and cells belonging to other tissue types. ...
Inflammation is the first response of the immune system to infection or irritation and may be referred to as the innate cascade. ...
In epidemiology, the morbidity rate is a ratio that measures the incidence and prevalence of a specific disease. ...
In the skin this can cause intense itching that leads to the skin becoming swollen and chronically thickened, a condition often called lizard skin. The skin may also become lax as a result of the loss of elastic fibres. Over time the skin may lose some of its pigment; on dark skin this gives rise to a condition known as leopard skin. Medicine In medicine, a persistent and lasting condition is said to be chronic (from Greek chronos). ...
There are separate articles about elasticity in economics, and about British rubber bands. ...
Melanin is a pigment ranging from brown to black in hue found in animals and plants. ...
The symptom that gives the disease its common name river blindness is also caused by the immune system's reaction to the microfilariae. 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, scelerosing 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 curved, transparent layer that covers the front part of the eye and protects its inner structures. ...
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 microfillariae 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 sold under brand names Stromectol® in the US and Mectizan® in Canada. ...
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 organsations such as the World Health Organisation to provide free mectizan to those who need it in endemic areas. 1988 is a leap year starting on a Friday of the Gregorian calendar. ...
Merck & Co. ...
For other meanings of the acronym WHO, see WHO (disambiguation) WHO flag Headquartered in Geneva, Switzerland, the World Health Organization (WHO) is an agency of the United Nations, acting as a coordinating authority on international public health. ...
Endemic, in a broad sense, can mean belonging or native to, characteristic of, or prevalent in a particular geography, race, field, area, or environment; Native to an area or scope. ...
There are various control programs that aim to stop onchocerciasis from being a public health problem. The first was the Onchocerciasis Control Program (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. C ontinued monitoring ensures that onchocerciasis cannot reinvade the area of the OCP. 1974 is a common year starting on Tuesday (click on link for calendar). ...
1988 is a leap year starting on a Friday of the Gregorian calendar. ...
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 of financing states. ...
The United Nations Development Programme (UNDP) is the largest multilateral source of grant technical assistance in the world. ...
Headquartered in Rome, Italy, the Food and Agriculture Organization (FAO) of the United Nations programs seek to raise levels of nutrition and standards of living; to improve the production, processing, marketing, and distribution of food and agricultural products; to promote rural development; and, by these means, to eliminate hunger. ...
2002 is a common year starting on Tuesday of the Gregorian calendar. ...
In 1992 the Onchocerciasis Elimination Programme for the Americas (OEPA) was launched. The OEPA also relies on ivermectin. 1992 is a leap year starting on Wednesday of the Gregorian calendar. ...
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 was a common year starting on Sunday of the Gregorian calendar. ...
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