Onchocerciasis (River Blindness)

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Jerry R. Balentine, DO, FACEP
    Jerry R. Balentine, DO, FACEP

    Jerry R. Balentine, DO, FACEP

    Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.

Onchocerciasis Symptoms and Signs

Bumps on the Skin

People often describe localized swollen areas on, or under, the skin as lumps or bumps. While bumps on, or under, the skin may result from conditions that give rise to a skin rash, many other conditions can result in solitary raised lumps on the skin. Infections, tumors, and the body's response to trauma or injury can all lead to lumps or bumps that appear to be located on or underneath the skin.

Onchocerciasis facts

  • Onchocerciasis is a parasitic disease that may cause blindness. It occurs mainly in sub-Saharan Africa and a few isolated areas in the Americas (Brazil, Colombia, Guatemala, Mexico, and Venezuela) and is transmitted by blackfly bites.
  • It is called river blindness as the blackfly that transmits the disease lives and breeds near fast-flowing rivers.
  • Symptoms include skin changes, itching, nodules, and alterations in vision.
  • Symptoms may not appear for months to years.
  • Onchocerciasis is diagnosed by finding the parasites in skin nodules, skin biopsies, or skin scrapings.
  • The treatment is the antiparasite drug ivermectin, given once or twice a year for about 10-15 years; the antibiotic doxycycline may also be utilized.
  • The major risk factor for onchocerciasis is residing or having extended visit time in areas where blackflies are endemic.
  • There are no vaccines or drugs that prevent onchocerciasis. Avoiding areas where blackflies are endemic and the use of personal protection items (clothing, insect repellents) reduce the chance of infection.
  • The earlier that onchocerciasis is diagnosed and treated, usually the better is the prognosis.
Photo of a blackfly
Photo of a blackfly; SOURCE: CDC

What is onchocerciasis?

Onchocerciasis is a parasitic disease caused by parasites (nematode) named Onchocerca volvulus. It is transmitted to humans by the bite (blood meal) of the female blackfly (Simulium). The disease is also termed river blindness because the vector, the blackfly, is usually found breeding close to rapidly flowing streams and rivers, and because the most devastating manifestation of the infection is blindness. Although the majority of people infected reside in sub-Saharan Africa (for example, Nigeria), it also occurs in Central and South American countries and Yemen but much less frequently. After trachoma, it is the second-leading cause of infection-caused blindness worldwide. The CDC classifies it in the Neglected Tropical Diseases category: a group of parasitic and bacterial disease that cause substantial illness in more than 1 billion patients.

Medically Reviewed by a Doctor on 9/16/2016

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