onchocerciasis

noun

on·​cho·​cer·​ci·​a·​sis ˌäŋ-kō-ˌsər-ˈkī-ə-səs How to pronounce onchocerciasis (audio)
ˌäŋ-kə-
plural onchocerciases
ˌäŋ-kō-ˌsər-ˈkī-ə-ˌsēz,
ˌäŋ-kə- How to pronounce onchocerciasis (audio)
: infestation with or disease caused by filarial worms (genus Onchocerca)
especially : a human disease marked by subcutaneous nodules, dermatitis, and visual impairment and caused by a worm (O. volvulus) found in Africa and tropical America which is transmitted by the bite of a female blackfly

called also river blindness

Examples of onchocerciasis in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Ivermectin subsequently proved extremely effective in treating tropical diseases such as onchocerciasis and lymphatic filariasis, which devastate and disfigure poor people around the world; as with eflornithine, the World Health Organization listed it as an essential medicine. Christopher B. Barrett, Foreign Affairs, 25 Sep. 2023 River blindness, or onchocerciasis, is caused by a parasitic worm that is spread by the bites of a small black fly that is common around rivers in much of Africa. Foreign Affairs, 10 Dec. 2020

Word History

Etymology

New Latin Onchocerca, genus of filarial worms (from oncho-, probably erroneously for onco-, from Greek ónkos "barb of an arrow" + -o- -o- + -kerka, feminine of -kerkos "having a tail [of the kind specified]," adjective derivative of kérkos "tail") + -iasis — more at angle entry 2, cercus

Note: The genus Onchocerca was introduced by the Austrian zoologist Karl Moriz Diesing (1800-67) in a brief Latin description of the worm Onchocerca reticulata appended to an article by J. Hermann, "Trichina, bei einem Pferde gefunden," Oesterreichische medicinische Wochenschrift, 1841, no. 9 (February 27), p. 199-200. Diesing's coinage is presumed to mean "hook-tailed," on the assumption that his oncho- is a mistake for onco-, but nothing in the description renders this self-evident. Perhaps the reference is to the spicule (copulatory organ) of the male.

First Known Use

1911, in the meaning defined above

Time Traveler
The first known use of onchocerciasis was in 1911

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Cite this Entry

“Onchocerciasis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/onchocerciasis. Accessed 20 Mar. 2025.

Kids Definition

Medical Definition

onchocerciasis

noun
: infestation with or disease caused by filarial worms of the genus Onchocerca
especially : a human disease marked by subcutaneous nodules, dermatitis, and visual impairment that is caused by a worm (O. volvulus) found in Africa and tropical America and transmitted by the bite of a female blackfly

called also onchocercosis, river blindness

see craw-craw

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