ISSN 2398-2977      

Onchocerca cervicalis

pequis

Introduction

Classification

Taxonomy

  • Phylum:Nematoda.
  • Superfamily:Filaroidea.
  • Genus:Onchocerca.
  • Species:cervicalis.

Active Forms

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Clinical Effects

Epidemiology

Lifecycle

  • Microfilariae in dermis.
  • Ingested by biting flies(Culicoides spp).
  • Develop to infective stage.
  • Deposited by fly on to skin during feeding.
  • Adult worms found in tendons/ligaments, typically nuchal ligament.

Transmission

  • Through feeding activity ofCulicoidesspp.

Pathological effects

  • The host response to dying worms may cause dermatitis with pruritus, alopecia, depigmentation and ulceration.
  • This immunopathologic response (mazzotti reaction) is characteristic of hypersensitivity responses to helminth parasites.
  • Parasite cuticle collagen components have been implicated in inducing such responsesviaaggregation of platelets and production of arachidonic acid metabolites.
  • Skin lesions (alopecia, scaling, crusting, inflammatory plaques, erythema, ulceration, lichenification, pruritus) are most usually seen on the forehead, ventral mid-line and pectoral region.
  • Sporadic cases involving the conjunctiva also occur.
  • Adult parasites in nodules are sometimes apparent as painless swellings in the nuchal ligament.

Other Host Effects

  • In general, infections are tolerated well with little pathology.
  • Horses that have clinical lesions have developed hypersensitivity.

Control

Control via animal

  • Fly avoidance measures - stabling of horses at dawn and dusk.
  • Fly control measures - repellents (eg in USA 2% permethrin products are very effective as repellents), insecticides.

Control via chemotherapies

  • Ivermectin   Ivermectin  is effective against microfilariae 200 micrograms/kg one dose (PO or IM), occasionally second and third dose may be necessary at 1 month interval.
  • Does not kill adults.
  • Repeated treatments advisable in areas where high rates of transmission occur.
    Treatment may precipitate clinical signs due to intense response to dying parasites
  • In clinical cases non-steroidal anti-inflammatory agents   Therapeutics: anti-inflammatory drugs  may be beneficial in reducing the pathology associated with the host inflammatory/immune response.

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mancebo O A, Verdi J H and Bulman G M (1997) Comparative efficacy of moxidectin 2% equine oral gel and ivermectin 2% equine oral paste against Onchocerca cervicalis (Raillet and Henry, 1910) microfilariae in horses with naturally acquired infections in Formosa (Argentina). Vet Parasitol 73 243-248 PubMed.
  • Klei T R, Torbert B, Chapman M R & Foil L (1983) Prevalence of Onchocerca cervicalis in equids in the Gulf Coast Region. Am J Vet Res 45 (8) 1646-1647 PubMed.
  • Lloyd S and Soulsby E J L (1978) Survey for infection with Onchocerca cervicalis in horses in eastern United States. Am J Vet Res 39, 1962-1963 PubMed.

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

 Security code