Equis ISSN 2398-2977

Skin: onchocerciasis

Contributor(s): Prof Derek Knottenbelt, Dawn Logas, Sue Paterson, David Senter

Introduction

  • Cause:Onchocerca cervicalis  Onchocerca cervicalis  .
  • Signs: alopecia, depigmentation, erythema and crusting on ventral midline, periorbitally and base of mane.
  • Diagnosis: history, clinical signs plus microfilaria in skin biopsy.
  • Treatment: ivermectin   Ivermectin  .
  • Prognosis: hair regrowth is good; uveitis will be exacerbated by sudden death of large numbers of microfilaria.

Pathogenesis

Etiology

  • Onchocerca cervicalis  Onchocerca cervicalis  .
  • Adults may cause initial mild reaction without clinical signs.
  • Microfilaria   →   inflammatory reaction.

Specific

  • Hornfly feeding on lesions exacerbates and prolongs condition.
  • Seasonal incidence.

Pathophysiology

  • Culicoidesspp inoculate L3   →   adults in ligamentum nuche   →   microfilaria migrate   →   dermis   →   mild to severe local inflammatory reaction depending on sensitivity of individual.
  • Exacerbated by feeding of hornfly (Hematobia irritans) .
  • Perivascular and periadnexal mononuclear and eosinophilic dermatitis with proliferation of fibroblasts   →   fibrosis, alopecia, depigmentation with chronic disease.

Timecourse

  • Adult has a 5 year lifespan.

Epidemiology

  • Typical filarial lifecycle.
  • Microfilaria occur in tissue spaces in skin.
  • Culicoidesspp act as vectors.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Monahan C M, Chapman M R, French D D & Klei T R (1995)Efficacy of moxidectin oral gel against Onchocerca cervicalis microfilariae.J Parasitol81(1), 117-8 PubMed.

Other sources of information

  • Scott D W & Miller W J Jr (2003)Equine Dermatology. Elsevier Science, St Louis, Missouri, USA.


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