Onchocerciasis: Difference between revisions
(Updated background, clinical features, diagnosis and treatment) |
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==Background== | ==Background== | ||
*'''Second most common cause of infectious blindness worldwide''' (~300,000 people worldwide | *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]] | **Second only to [[Trachoma]] | ||
**99% of infected individuals live in Africa | **99% of infected individuals live in Africa | ||
*Caused by Onchocerca | *Caused by ''Onchocerca volvulus'' | ||
**A round worm (Nematode) | **A round worm (Nematode) | ||
*Spread by the black fly (genus Simulium) | *Spread by the black fly (genus Simulium) | ||
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==Clinical Features== | ==Clinical Features== | ||
[[File:PMC3206119 opth-5-1479f3.png|thumb|Sclerosing keratitis from onchocerciasis.]] | |||
[[File:PMC2041822 pntd.0000074.g001.png|thumb|Palpable onchocercal nodule.]] | |||
[[File:PMC2041822 pntd.0000074.g002.png|thumb|Onchocercal skin disease.]] | |||
[[File:PMC3655252 IJPA-8-145-g004.png|thumb|Leopard skin.]] | |||
*Mainly consist of cutaneous and ocular symptoms secondary to the inflammation reactions from migration of the larvae or death of the larvae | *Mainly consist of cutaneous and ocular symptoms secondary to the inflammation reactions from migration of the larvae or death of the larvae | ||
===Cutaneous manifestations=== | ===Cutaneous manifestations=== | ||
*Pruritis | *Pruritis | ||
*Onchodermatitis | *Onchodermatitis - pruritic cutaneous nodules (may be acute or chronic) | ||
*Elephant skin - skin thickening | |||
*Elephant skin | *Lizard skin - skin atrophy and wrinkling | ||
*Leopard skin - areas of depigmentation | |||
*Lizard skin | |||
*Leopard skin | |||
===Ocular manifestations=== | ===Ocular manifestations=== | ||
*Thought to be caused by migration of the microfilariae to the corneal surface | *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) | **Some evidence exists to suggest that the ocular manifestations are from the immune response to Wolbachia (an endosymbiant to Onchocera) | ||
==Differential Diagnosis== | |||
{{Travel Skin Conditions DDX}} | |||
== | ==Evaluation== | ||
*Skin snip | *Skin snip | ||
**Multiple small (1-2 gm) snips are placed in normal saline and presence of microfilariae detected | **Multiple small (1-2 gm) snips are placed in normal saline and presence of microfilariae detected | ||
**Can PCR biopsy if negative for microfilariae | **Can PCR biopsy if negative for microfilariae | ||
*Mazotti test | *Mazotti test | ||
**Place diethylcarbazine (DEC) on patch of skin - localized | **Place diethylcarbazine (DEC) on patch of skin - localized pruritus and urticaria are positive reactions | ||
== | ==Management== | ||
*Ivermectin | *[[Ivermectin]] | ||
**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== | |||
*[http://www.who.int/topics/onchocerciasis/en/ World Health Organization - Onchocerciasis] | |||
== | ==References== | ||
<references/> | |||
[[Category:ID]] | [[Category:ID]] | ||
[[Category: | [[Category:Tropical Medicine]] | ||
Latest revision as of 13:19, 12 December 2020
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