ISSN 2398-2977      

Skin: onchocerciasis

pequis

Introduction

  • CauseOnchocerca cervicalis Onchocerca cervicalis, O. gutturosa, O. reticulata Onchocerca spp.
  • Signs: alopecia, depigmentation, erythema, scaling and crusting on ventral midline, on the head and base of mane. Variable pruritus, other signs include nodules on limbs, keratitis and uveitis.
  • Diagnosis: history, clinical signs plus microfilaria in skin biopsy.
  • Treatment: ivermectin or moxidectin.
  • Prognosis: hair regrowth is good; uveitis will be exacerbated by sudden death of large numbers of microfilaria.

Pathogenesis

Etiology

  • Onchocerca cervicalis Onchocerca cervicalisO. gutturosa, O. reticulata Onchocerca spp.
  • Adults may cause initial mild reaction without clinical signs.
  • Microfilaria → inflammatory reaction.

Predisposing factors

Specific

  • Horn fly feeding on lesions exacerbates and prolongs condition.
  • Seasonal incidence.

Pathophysiology

  • Culicoides spp inoculate L3 → adults in ligamentum nuche → microfilaria migrate → dermis → mild to severe local inflammatory reaction depending on sensitivity of individual.
  • Exacerbated by feeding of Horn fly (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.
  • Culicoides spp and Simulium spp act as vectors.
  • Onchocerca spp may be found in healthy individuals.

Diagnosis

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mansell S E & Behnke M C (2022) Onchocerca cervicalis: A survey into awareness and knowledge of the parasite amongst UK equine veterinarians. J Equine Vet Sci 114 PubMed.
  • Monahan C M, Chapman M R, French D D & Klei T R (1995) Efficacy of moxidectin oral gel against Onchocerca cervicalis microfilariae. J Parasitol 81 (1), 117-118 PubMed.
  • Polley L (1984) Onchocerca in horses from Western Canada and the Northwestern United States: An abattoir survey of the prevalence of infection. Can Vet J 25, 124-129 PubMed.

Other sources of information

  • Scott D W & Miller W H (2011) Equine Dermatology. 2nd edn. Saunders, USA.
  • Knottenbelt D C (2009) Pascoe’s Principles and Practice of Equine Dermatology. 2nd edn. Ed: Knottenbelt D C. Saunders, USA.
  • Scott D W & Miller W J Jr (2003) Equine Dermatology. Elsevier Science, USA.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field