Equis ISSN 2398-2977

Dictyocaulus arnfieldi

Contributor(s): Maggie Fisher, Sheelagh Lloyd

Introduction

Classification

Taxonomy

  • Phylum: Nematoda.
  • Superfamily: Trichostrongyloidea.
  • Family: Dictyocaulidae.
  • Genus: Dictyocaulus.
  • Species: arnfieldi.

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Clinical Effects

Epidemiology

Habitat

  • Infective larvae usually disappear from the grass during winter.
  • Pasture reinfected following spring by freshly passed larvae or by re-emergence of larvae that migrated into the soil.

Lifecycle

  • Embryonated egg.
  • 1st, 2nd and 3rd stage larvae on pasture.
  • 3rd stage larvae infective - ingested off pasture by equidae.
  • 3rd and 4th stages in equine host - migrate from GIT to lungs.
  • Adults in bronchi.
  • Prepatent period 2-3 months.

Transmission

  • Ingestion of L3 larvae from pasture.
  • Increasing numbers in second half of summer and autumn.
  • Usually transmission donkey to horse, or donkey to donkey.
  • Less commonly horse to horse or to donkey as horses less likely to have patent infection, although horse to horse tranmission is known to occur in many countries.

Pathological effects

  • Horses appear to be poorer host for parasite, worms may be prevented from egg-laying despite reaching maturity. Disease immunologically mediated.
  • Infection may be associated with slight increase in lung sounds in donkeys.
  • Unclear if infection causes respiratory intolerance in donkeys when exercised.
  • Infection in horses associated with persistent cough and increased respiratory rate and possibly nasal discharge.
  • Adult nematodes in bronchial tree - can cause chronic bronchitis.
  • Presence associated with purulent mucus and eosinophils in bronchial tree.

Other Host Effects

  • Donkeys - appear to be well adapted parasite of donkeys.
  • Donkeys can harbour parasite without clinical signs or with very mild respiratory signs.

Control

Control via animal

  • Graze untreated donkeys and horses separately.
  • Treat donkeys with suitable anthelmintic.

Control via chemotherapies

  • Anthelmintics:
    • Ivermectin   Ivermectin  - 200 mcg/kg licensed claim vs adult and immature lungworm.
    • Fenbendazole   Fenbendazole  - 15-30 mg/kg (not licensed for this purpose).
    • Mebendazole   Mebendazole  - 15-20 mg/kg for 5 days - Telmin has license indication for the treatment of donkeys.
  • Mebendazole   Mebendazole  has been found to be 75-100% effective at the above dose rate for the treatment of donkeys.

Control via environment

  • Separate grazing of untreated donkeys and horses.
  • Anthelmintic treatment coupled with slow rotation of grazing paddocks (as larvae will survive on pastures for extended periods).

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lester G (1993) Diagnostic dilemma case presentation (verminous bronchitis in a horse)Comp Contin Educ Prac Vet 15, 737-741 VetMedResource.
  • Britt D P & Preston J M (1985) Efficacy of ivermectin against Dictyocaulus arnfieldi in ponies. Vet Rec 116, 343-345 PubMed.

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