Onchocerciasis-river blindness

River blindness is caused by Onchocerca volvulus, filarial nematode worms that are transmitted by the bite of an infected blackfly. Around 198 million people live in regions at risk of river blindness, as of 2016. Onchocerciasis is a neglected tropical disease which is still of immense major public health concern in several areas of Africa and the Americas.

The flies transmit juvenile worms, or microfilariae, into the host, which can cause severe itching, disfiguring skin lesions, and impaired vision – all symptoms that cause immense suffering. Repeated infection causes eye disease that can lead to blindness.

Highly pruritic, papular dermatitis; subcutaneous nodules; lymphadenitis; and ocular lesions, which can progress to visual loss and blindness. Symptoms begin after patent infections are established, which may take 18 months. Symptoms in travelers are primarily dermatologic (rash and pruritus) and may occur years after departure from endemic areas. Subcutaneous nodules are more common in endemic populations.

River blindness affects people living in mostly remote and underserved rural communities in some of the poorest areas of the world. It can cause irreversible blindness and severe skin disease in those who have very little to start with and making them poorer.

Onchocerciasis-river blindness

Onchocerciasis

Onchocerciasis is a cumulative disease: in a given bioclimatic area the severity of lesions are related to the mean intensity of infection of the human communities by Onchocerca volvulus itself dependent on the density of infective biting vector. Onchocerca volvulus is a filarial nematode that lives for up to 14 years in the human body.

Each adult female worm (thin but more than 50 cm in length) produces millions of microfilariae that migrate throughout the body and give rise to visual impairment (punctuate keratitis), rashes, intense pruritis and depigmentataion of the skin; lymphadenitis; “hanging groin” and elephantiasis of the genitals.

Although corneal inflammation (keratitis) accounts for most cases of blindness, the parasites can also induce damage to posterior sections of the eye, including the choroid, retina and optic nerve.

Onchocerciasis is a disabling and debilitating disease which affects more severely small rural communities. In Savannah African valleys, onchocerciasis blinding rates may affect up to 10% of the total population

An estimated 169,196,267 Africans were at risk for onchocerciasis as of 2013. A mass treatment program was initiated in West Africa in 1974, resulting in 1.5 million cured and 400,000 cases blindness prevented to 1998.
Onchocerciasis