Onchocerciasis (river blindness)

 

Onchocerciasis (River blindness)

Definition

Onchocerciasis is a disease of the eyes and skin caused by a worm, whose scientific name is Onchocerca volvulus.

 

Organ

Onchocerciasis causes lesions of the cornea.

 

Symptoms

Dermatologically, it causes itching, rashes, and subcutaneous nodules appear.

In the eye, it causes itching, redness, lesions affecting the cornea and retina, and an optic nerve damage resulting in decreased vision.

 

Frequency

Onchocerciasis is a major cause of blindness in many African countries. As a public health problem, the disease is most closely associated with West and Central Africa, but it is also prevalent in Yemen and six countries in Latin America. Onchocerciasis has in the past greatly reduced the economic productivity in infected areas and left vast tracts of arable land abandoned. It is estimated that there are about half a million blind people due to river blindness.

Source : WHO

 

The vast majority of infections occur in sub-Saharan Africa, with a small number of cases in the Middle East (notably Yemen) and in Central and South America.

Source : Kids New to Canada

 

Causes

Onchocerciasis is an insect-borne disease caused by a parasite Onchocerca volvulus and transmitted by blackflies of the species Simulium damnosum. Onchocerciasis is often called “river blindness” because the blackfly which transmits the disease abounds in fertile riverside areas, that frequently remain uninhabited for fear of infection. O. volvulus is almost exclusively a parasite of man. Adult worms live in nodules in a human body where the female worms produce high numbers of first-stage larvae known as microfilariae. They migrate from the nodules to the sub-epidermal layer of the skin where they can be ingested by blackflies. They further develop in the body of the insect from which more people can be infected. Eye lesions in humans are caused by microfilariae. They can be found in all internal tissues of the eye -- except the lens -- where they cause eye inflammation, bleeding, and other complications that ultimately lead to blindness.

Source : WHO 

 

People who live in rural areas near fast-flowing rivers and streams in an endemic region (especially Sub-Saharan Africa) are at highest risk of infection.

Source : Kids New to Canada

 

Evolution

Without treatment, reversible lesions on the cornea can lead to permanent clouding of the cornea and blindness. Inflammation of the optic nerve can also lead to vision loss and blindness. Long-term damage to skin can result in scattered rashes, hyperpigmentation (which may be associated with edema), skin atrophy (thinning of the skin with loss of elasticity) and depigmentation (which can look like “leopard skin”, especially on the lower legs). Persistent and severe itchiness can contribute to chronic insomnia or depression.

Source : Kids New to Canada

 

Prevention

Although river blindness was put on the priority disease list of VISION 2020, global initiatives had already been taken for onchocerciasis control. Beginning in 1974, effective vector control was implemented in West Africa through the Onchocerciasis Control Programme (OCP). Since 1996 mass community-based ivermectin treatment control programmes have been introduced by the African Programme for Onchocerciasis Control (APOC) in many other African countries and by the Onchocerciasis Elimination Programme in the Americas (OEPA) in the affected Latin American Countries. In 1992 an NGDO (Non-Governmental Development Organization) group, now called the Nongovernmental Development Organizations Coordination Group for Onchocerciacis Control, was formed to help promote worldwide interest and support for the use of ivermectin in endemic countries to eliminate onchocerciasis as a public health problem. Currently consisting of 9 international and 1 national partner NGDOs, the Group's activities are coordinated via its secretariat at WHO/HQ. Onchocerciasis control is not only an ongoing success story of disease control but also demonstrates the value of the synergy that comes from working together in partnership, and the economic return and social development that results from investments made in a disease control programme.

Source : WHO 

 

Diagnosis

Dermatologically, a biopsy is performed.

At eye level, a review of the previous room to the slit lamp is required.

 

Treatment

The fight against onchocerciasis in environmental terms is to kill the larvae with insecticides, including the dispersal of insecticides on rivers and streams.

Onchocerciasis is treated with ivermectin, which kills microfiliaires, soothes itching and halts the progression to blindness. It also reduces transmission by preventing reproduction.

A single annual dose of the treatment is effective.

 

 

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