Onchocerciasis
MICROBIOLOGY
- Onchocerciasis is caused by filarial worm Onchocerca volvulus.
- Epidemiology: the world’s second-leading cause of blindness.
- Approximately 18 million people are infected, and nearly one million have been permanently blinded or suffer severe visual impairment.
- 99% of onchocerciasis cases occur in Africa.
- Disease is endemic in 31 countries in sub-Saharan Africa, plus Venezuela, Brazil, and Yemen; WHO certified Columbia (2013), Ecuador (2014), Mexico (2015), and Guatemala (2016) to be free of human onchocerciasis.
- O. volvulus transmitted to humans by blackflies (Simulium damnosum), which breed in fast-flowing rivers and streams.
- Life cycle:
- Infected blackfly transmits third-stage filarial larvae onto the skin of the human host during a blood meal.
- Larvae penetrate the subcutaneous tissues and develop into adult microfilariae over 6-12 months.
- Adults persist in subcutaneous nodules for about 15 years, with females producing 1,000-3,000 microfilariae per day for up to 9 years.
- Blackfly ingests microfilariae during a blood meal.
- Microfilariae penetrate the blackfly midgut and migrate to thoracic muscles, where they develop into first-stage larvae and then third-stage larvae.
- Third-stage larvae migrate to the blackfly proboscis and can infect another human host during a blood meal.
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Last updated: January 12, 2020
Citation
Crowell, Trevor A, and Paul G Auwaerter. "Onchocerciasis." Johns Hopkins ABX Guide, The Johns Hopkins University, 2020. Pediatrics Central, peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540397/all/Onchocerciasis.
Crowell TA, Auwaerter PG. Onchocerciasis. Johns Hopkins ABX Guide. The Johns Hopkins University; 2020. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540397/all/Onchocerciasis. Accessed June 3, 2023.
Crowell, T. A., & Auwaerter, P. G. (2020). Onchocerciasis. In Johns Hopkins ABX Guide. The Johns Hopkins University. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540397/all/Onchocerciasis
Crowell TA, Auwaerter PG. Onchocerciasis [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2020. [cited 2023 June 03]. Available from: https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540397/all/Onchocerciasis.
* Article titles in AMA citation format should be in sentence-case
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Y1 - 2020/01/12/
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PB - The Johns Hopkins University
DB - Pediatrics Central
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