River Blindness

Brain & Nerve
Eye & Vision
Contributed byMaulik P. Purohit MD MPHMar 11, 2021

What are the other Names for this Condition? (Also known as/Synonyms)

  • African River Blindness
  • Onchocerciasis
  • Robles Disease

What is River Blindness? (Definition/Background Information)

  • River Blindness or Onchocerciasis is a type of roundworm infection caused by Onchocerca volvulus (a parasite). It is a vector-borne infection that is transmitted by an infected blackfly, known as simulium
  • The condition is mostly endemic to many regions of Africa and frequently affects those living near rivers and streams, which are fast-moving
  • The parasitic worm O. volvulus can cause itchy skin rashes, signs and symptoms involving the eye, and firm nodules just below the skin
  • Treatment of River Blindness involves the use of the anti-parasitic medication ivermectin, which can result in a complete cure. Longstanding infections that remain untreated may lead to permanent blindness

Who gets River Blindness? (Age and Sex Distribution)

  • River Blindness infects all individuals, irrespective of age, gender, race, or ethnicity
  • The disease is especially observed among people, who live in the tropical areas of Africa (a large percentage of infections take place in sub-Saharan Africa), Middle East, and some parts of South America, where River Blindness is endemic

What are the Risk Factors for River Blindness? (Predisposing Factors)

Following are the risk factors for River Blindness:

  • Living in the tropical areas, where River Blindness is endemic
  • Travelers who visit the endemic regions for extended time periods (such as for over 3 months) have a high risk
  • Those living near fast-moving water bodies such as rivers and streams (in the endemic regions), since blackflies are found near such water bodies
  • Individuals with very weak immune system, such as those with HIV infection and AIDS, are at a higher risk

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of River Blindness? (Etiology)

  • River Blindness may be described as a type of filarial roundworm infection that is caused by the bite of an infected female blackfly
  • Typically, one bite by the infected blackfly does not result in an infection. Studies have revealed that an individual has to receive multiple bites before the signs and symptoms of River Blindness can be manifested
  • The parasitic roundworm Onchocerca volvulus (larva) enters the skin when the fly bites (repeatedly), which results in River Blindness

What are the Signs and Symptoms of River Blindness?

Once an individual is infected, it may take up to a year for the individual to present with the signs and symptoms of River Blindness. The most common signs and symptoms may include:

  • Severe itchiness that can lead to skin rashes and loss of sleep
  • Skin lesions are pruritic papules, hyperpigmented patches, irregular pigmentation of skin (leopard skin), and skin atrophy
  • Formation of subcutaneous nodules
  • Thickening of the skin due to lymph edema, especially in the groin region (known as hanging groin)
  • Eye signs and symptoms that include redness (conjunctivitis), pain in the eye, glaucoma-like symptoms due to increased pressure in the eye

It is important to note that the parasite can affect any part of the eye.

How is River Blindness Diagnosed?

A diagnosis of River Blindness would involve the following exams and tests:

  • Complete physical examination with medical history evaluation (including history of recent travel)
  • Blood tests to detect antibodies against the parasite: If an individual has a positive antibody blood test, it does not mean that the individual has an active infection. It might indicate that the individual may have been infected in the past. Hence, in such cases, the healthcare provider combines the physical findings and laboratory tests to arrive at a definitive diagnosis
  • Skin biopsy: A skin biopsy is performed and sent to a laboratory for a pathological examination, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. However, if the skin biopsy is negative, it does not indicate that the individual does not have River Blindness
  • If brain or neurological signs and symptoms are observed, then imaging studies, such as EEG of brain, cerebrospinal fluid analysis, and MRI of brain, may be undertaken
  • Ultrasound scan of the skin nodules
  • Molecular test to detect the parasites can help confirm the diagnosis
  • Ophthalmologic (eye) exam: Before the eye exam is performed, the individual may be asked to rest their head on their knees for a few minutes. This causes the roundworm to appear in the anterior chamber of the eye, making it easier for the healthcare provider to visualize the parasites during the eye exam. Optic nerve damage, if any present, may also be detected

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of River Blindness?

River Blindness can cause the following complications:

  • Inflammation of the eye can cause the cornea to become opaque leading to blindness
  • If the parasite infects the brain, then it can cause convulsions, neurological symptoms, and affect cognitive function
  • Severe scratching of the skin can lead to secondary infections due to bacteria or fungus
  • Intense itching and significant lack of sleep may even cause individuals to commit suicide

How is River Blindness Treated?

  • River Blindness is treated using anti-parasitic medications, such as ivermectin, which can bring about a complete cure. The treatment may last for several months or years, depending upon the individual’s specific health condition
  • Corneal transplant may be required if blindness is caused by damage to the cornea
  • Since the infection can be longstanding, periodic medical checkups and follow-up appointments are important and necessary

How can River Blindness be Prevented?

River Blindness is a vector-borne disease, which is preventable by avoiding the bite of the infected female blackfly. The following measures are useful in controlling transmission of the condition:

  • Sleeping under insecticide-treated ‘mosquito nets’ is a highly recommended practice in endemic areas; also, one must avoid sleeping outdoors
  • Spraying the residence with DDT and other recommended insecticides
  • Use of insect-repellent creams
  • It is also advisable to cover the exposed arms and feet by wearing full-length pants, full-sleeved shirts, etc.
  • Maintain good sanitary conditions to prevent breeding of blackflies
  • Sprays containing permethrin can be used on clothes; sprays containing DEET can be used on the skin
  • Individuals traveling from non-endemic regions to endemic regions have to be made aware of the risk factors and basic preventive methods

Currently, there is no vaccine available against River Blindness.

What is the Prognosis of River Blindness? (Outcomes/Resolutions)

  • River Blindness, with early detection and proper treatment using suitable medications is completely curable and the prognosis is excellent
  • In general, River Blindness is not a fatal condition. Nevertheless, this roundworm infection is a prominent cause of blindness in the endemic regions, due to a lack of treatment or a delay in treatment (when infections last for a long period of time)
  • If the optic nerve is damaged, then it can result in permanent blindness. But, if the cornea is damaged, then a corneal transplant may be necessary to restore vision

Additional and Relevant Useful Information for River Blindness:

  • According to the World Health Organization (WHO), River Blindness is categorized as a “Neglected Tropical Disease”
  • According to the World Health Organization (WHO) 2008 statistics, it is estimated that over 25 million people were infected in the endemic regions (mostly in Africa) by the parasite, approximately 300,000 became blinded, and nearly 1 million had visual disturbances
  • William Campbell and Satoshi Omura got Nobel Prize in Medicine (in 2015) for discovering the drug ‘ivermectin’, along with researcher Tu Youyou (who discovered the medication against malaria)
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Maulik P. Purohit MD MPH

Assistant Medical Director, Medical Editorial Board, DoveMed Team


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