ISSN 2398-2993      

Malignant catarrhal fever

obovis

Synonym(s): MCF


Introduction

  • Cause: caused in the UK by Ovine Herpes Virus-2 (OHV2) and in Africa by Alcephaline Herpes Virus-1 (AlHV-1), for which wildebeest are the reservoir.
  • Signs: acute onset illness with depression, anorexia, pyrexia and oculo-nasal discharge.
  • Diagnosis: history of sheep contact, characteristic clinical signs and confirmation by PCR.
  • Treatment: euthanasia, on welfare grounds.
  • Prognosis: extremely poor (chronic cases have been reported that survive > 800 days).

Pathogenesis

Etiology

  • Caused in the UK by Ovine Herpes Virus-2 (OHV2), for which sheep are the reservoir.
  • It is a major limitation to cattle farming in parts of Africa, where it is caused by Alcephaline Herpes Virus-1 (AlHV-1), for which wildebeest are the reservoir.

Predisposing factors

General

  • Housing cattle and sheep together is a major risk factor.

Pathophysiology

  • A study of MCF lesions in 11 beef cattle surviving for between 39 and >800 days identified the following lesions:
    • Subacute-chronic MCF (5 cows examined):
      • All examined cows showed signs of ophthalmitis, including: stromal keratitis, uveitis and retinitis .
      • All examined cows had erosions of the proximal GIT and encephalitis. 3/5 cows also had erosions of the distal GIT.
      • All examined cows had arteriopathic lesions. Arteriosclerosis was the most consistent lesion, whilst lymphoid vasculitis and fibrinoid necrosis were less consistent.
      • Other lesions found include: necrotising dermatitis, serous fat atrophy, lymphadenopathy, unilateral perforating keratitis, unilateral iridial prolapse, acute necrotic splenitis and bilateral pigmentary keratitis.
  • MCF with recovery (5 cows examined):
    • All examined cows showed signs of arteriosclerosis, whilst lymphoid vasculitis was less consistent. None of the cows suffered from fibrinoid necrosis.
    • All examined cows suffered from ophthalmitis, with stromal keratitis the most consistent finding. Uveitis and retinitis were present in 4/5 animals.
    • 4/5 cows had proximal GIT ulceration and encephalitis, however only one had distal GIT ulceration.
    • Other lesions found include: unilateral perforating keratitis, unilateral iridial prolapse, atrophy of seminiferous tubules, severe bilateral pigmentary keratitis and atrophy in ovarian follicles.

Epidemiology

  • MCF is a relatively rare, sporadic disease in the UK affecting cattle and deer.
  • Outbreaks can occur, but usually only a single case is seen.
  • Contact with sheep or goats (especially around lambing) seems to be necessary for transmission of the disease to cattle.
  • There are high rates of seropositivity in sheep, but the route of transmission is unknown.
  • Cases of MCF may occur months after contact with sheep, suggesting prolonged incubation or latent infection.
  • The virus is very fragile and will not survive for more than a day outside the host.
  • Cattle are considered ‘dead - end’ hosts and are not thought to transmit MCF.

Diagnosis

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Treatment

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Prevention

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • O'Toole et al (1997) Chronic and recovered cases of sheep-associated malignant catarrhal fever in cattle. Vet Rec 140 (20), 519-524 PubMed.

Organisation(s)

  • The Royal (Dick) School of Veterinary Studies.

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