Onchocerciasis: Difference between revisions
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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=== | ||
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