Onchocerciasis: Difference between revisions
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==Background== | ==Background== | ||
*Also known as "river blindness" | *Also known as "river blindness" | ||
*'''Second most common cause of infectious blindness worldwide''' (~300,000 people worldwide | *'''Second most common cause of infectious blindness worldwide''' (~300,000 people worldwide - another ~800,000 have visual disturbances) | ||
**Second only to [[Trachoma]] | **Second only to [[Trachoma]] | ||
**99% of infected individuals live in Africa | **99% of infected individuals live in Africa | ||
| Line 38: | Line 38: | ||
**150mcg/kg one time dose | **150mcg/kg one time dose | ||
**Usually distributed in endemic areas as part of a mass drug administration (2 doses 6 months apart, every three years) | **Usually distributed in endemic areas as part of a mass drug administration (2 doses 6 months apart, every three years) | ||
==Disposition== | |||
*Discharge | |||
==See Also== | ==See Also== | ||
*[[Parasites]] | *[[Parasites]] | ||
*[[Travel | *[[Travel medicine]] | ||
==External Links== | ==External Links== | ||
Revision as of 02:42, 25 December 2016
Background
- Also known as "river blindness"
- Second most common cause of infectious blindness worldwide (~300,000 people worldwide - another ~800,000 have visual disturbances)
- Second only to Trachoma
- 99% of infected individuals live in Africa
- Caused by Onchocerca volvulus
- A round worm (Nematode)
- Spread by the black fly (genus Simulium)
- Bite during the day time
- Live in and near fast flowing streams and rivers
Clinical Features
- Mainly consist of cutaneous and ocular symptoms secondary to the inflammation reactions from migration of the larvae or death of the larvae
Cutaneous manifestations
- Pruritis
- Onchodermatitis - pruritic cutaneous nodules (may be acute or chronic)
- Elephant skin - skin thickening
- Lizard skin - skin atrophy and wrinkling
- Leopard skin - areas of depigmentation
Ocular manifestations
- Localized punctate keratitis that can become sclerosing keratitis → opacification of the cornea
- Thought to be caused by migration of the microfilariae to the corneal surface
- Some evidence exists to suggest that the ocular manifestations are from the immune response to Wolbachia (an endosymbiant to Onchocera)
Differential Diagnosis
- Papules
- Insect bites
- Scabies
- Seabather's eruption
- Cercarial dermatitis (Swimmer's Itch)
- Macular
- Sub Q Swelling and Nodules
- Ulcers
- Tropical pyoderma
- Leishmaniasis
- Mycobacterium marinum
- Buruli ulcer
- Dracunculiasis (Guinea Worm disease)
- Linear and Migratory Lesions
- Cutaneous larvae migrans
- Photodermatitis
See also domestic U.S. ectoparasites
Evaluation
- Skin snip
- Multiple small (1-2 gm) snips are placed in normal saline and presence of microfilariae detected
- Can PCR biopsy if negative for microfilariae
- Mazotti test
- Place diethylcarbazine (DEC) on patch of skin - localized pruritus and urticaria are positive reactions
Management
- Ivermectin
- 150mcg/kg one time dose
- Usually distributed in endemic areas as part of a mass drug administration (2 doses 6 months apart, every three years)
Disposition
- Discharge