Onchocerciasis

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Onchocerciasis
Other namesRiver blindness, Robles disease
An adult black fly with the parasite Onchocerca volvulus coming out of the insect's antenna, magnified 100×
Pronunciation
SpecialtyInfectious disease
SymptomsItching, bumps under the skin, blindness[1]
CausesOnchocerca volvulus spread by a black fly[1]
PreventionAvoiding bites (insect repellent, proper clothing)[2]
MedicationIvermectin, doxycycline[3][4]
Frequency15.5 million (2015)[5]

Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm Onchocerca volvulus.[1] Symptoms include severe itching, bumps under the skin, and blindness.[1] It is the second-most common cause of blindness due to infection, after trachoma.[6]

The parasitic worm is spread by the bites of a black fly of the Simulium genus.[1] Usually, many bites are required before infection occurs.[7] These flies live near rivers, hence the common name of the disease.[6] Once inside a person, the worms create larvae that make their way out to the skin, where they can infect the next black fly that bites the person.[1] There are a number of ways to make the diagnosis, including: placing a biopsy of the skin in normal saline and watching for the larva to come out; looking in the eye for larvae; and looking within the bumps under the skin for adult worms.[8]

A vaccine against the disease does not exist.[1] Prevention is by avoiding being bitten by flies.[2] This may include the use of insect repellent and proper clothing.[2] Other efforts include those to decrease the fly population by spraying insecticides.[1] Efforts to eradicate the disease by treating entire groups of people twice a year are ongoing in a number of areas of the world.[1] Treatment of those infected is with the medication ivermectin every six to twelve months.[1][3] This treatment kills the larvae but not the adult worms.[4] The antibiotic doxycycline weakens the worms by killing an associated bacterium, Wolbachia, and is recommended by some as well.[4] The lumps under the skin may also be removed by surgery.[3]

According to the Center for Disease Control and Prevention, as of 2017, about 20.9 million people were infected with Onchocerciasis, and an estimated 1.15 million have some amount of loss of vision from the infection.[7] Most infections occur in sub-Saharan Africa, although cases have also been reported in Yemen and isolated areas of Central and South America.[1] In 1915, the physician Rodolfo Robles first linked the worm to eye disease.[9] It is listed by the World Health Organization (WHO) as a neglected tropical disease.[10] In 2013 Colombia became the first country to eradicate the disease.[10]

  1. ^ a b c d e f g h i j k "Onchocerciasis Fact sheet N°374". who.int. World Health Organization. March 2014. Archived from the original on 16 March 2014. Retrieved 20 March 2014.
  2. ^ a b c "Onchocerciasis (also known as River Blindness) Prevention & Control". CDC.gov. US: Centers for Disease Control and Prevention. May 21, 2013. Archived from the original on 19 April 2014. Retrieved 20 March 2014.
  3. ^ a b c Murray P (2013). Medical microbiology (7th ed.). Philadelphia: Elsevier Saunders. p. 792. ISBN 978-0-323-08692-9. Archived from the original on 2017-09-08.
  4. ^ a b c Brunette GW (2011). CDC Health Information for International Travel 2012: The Yellow Book. Oxford University Press. p. 258. ISBN 978-0-19-983036-7. Archived from the original on 2017-09-08.
  5. ^ Vos T, Allen C, Arora M, et al. (8 October 2016). "Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015". The Lancet. 388 (10053): 1545–1602. doi:10.1016/S0140-6736(16)31678-6. PMC 5055577. PMID 27733282.
  6. ^ a b "Parasites: Onchocerciasis (also known as River Blindness)". CDC.gov. US: Centers for Disease Control and Prevention. 21 May 2013. Archived from the original on 26 February 2014. Retrieved 20 March 2014.
  7. ^ a b "Parasites – Onchocerciasis (also known as River Blindness) Epidemiology & Risk Factors". CDC.gov. US: Centers for Disease Control and Prevention. 21 May 2013. Archived from the original on 19 April 2014. Retrieved 20 March 2014.
  8. ^ "Onchocerciasis (also known as River Blindness) Diagnosis". CDC.gov. US: Centers for Disease Control and Prevention. 21 May 2013. Archived from the original on 19 April 2014. Retrieved 20 March 2014.
  9. ^ Lok, James B., Walker, Edward D., Scoles, Glen A. (2004). "9. Filariasis". In Eldridge, Bruce F., Edman, John D., Edman, J. (eds.). Medical entomology (Revised ed.). Dordrecht: Kluwer Academic. p. 301. ISBN 978-1-4020-1794-0. Archived from the original on 2017-09-08.
  10. ^ a b "Onchocerciasis (river blindness)". who.int. World Health Organization. 11 January 2022. Retrieved 2022-02-06.