Onchocerciasis: Difference between revisions
(Updated background, clinical features, diagnosis and treatment) |
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==Background== | |||
*'''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 | |||
Leopard skin | ===Cutaneous manifestations=== | ||
*Pruritis | |||
*Onchodermatitis | |||
**pruritic cutaneous nodules (may be acute or chronic) | |||
*Elephant skin | |||
**Thickening of the skin | |||
*Lizard skin | |||
**Atrophy and wrinkling of the skin | |||
*Leopard skin | |||
**Areas of depigmentation | |||
===Ocular manifestations=== | |||
*Thought to be caused by migration of the microfilariae to the corneal surface | |||
**Causes localized punctate keratitis that can become sclerosing keratitis leading to opacification of the cornea | |||
*Some evidence exists to suggest that the ocular manifestations are from the immune response to Wolbachia (an endosymbiant to Onchocera) | |||
Mazotti test | ==Diagnosis== | ||
*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 pruritis and urticaria are positive reactions | |||
==Treatment== | |||
*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) | |||
==See Also== | ==See Also== | ||
*[[Parasites]] | *[[Parasites]] | ||
*[[Travel Medicine]] | *[[Travel Medicine]] | ||
==Source== | |||
*http://www.who.int/topics/onchocerciasis/en/ | |||
*[[Wikipedia:Onchocerciasis]] | |||
*http://www.cdc.gov/parasites/onchocerciasis/ | |||
*Uptodate | |||
[[Category:ID]] | [[Category:ID]] | ||
[[Category:TropMed]] | [[Category:TropMed]] | ||
Revision as of 04:00, 2 December 2013
Background
- 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
- Thickening of the skin
- Lizard skin
- Atrophy and wrinkling of the skin
- Leopard skin
- Areas of depigmentation
Ocular manifestations
- Thought to be caused by migration of the microfilariae to the corneal surface
- Causes localized punctate keratitis that can become sclerosing keratitis leading to opacification of the cornea
- Some evidence exists to suggest that the ocular manifestations are from the immune response to Wolbachia (an endosymbiant to Onchocera)
Diagnosis
- 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 pruritis and urticaria are positive reactions
Treatment
- 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)