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Malignant catarrhal fever: the disease
Synonym(s): Herpes, wildebeest, sheep, keratitis, conjunctivitis, blindness, stomatitis, pneumonia
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).
Age predisposition
- None.
Breed/Species predisposition
- None.
Public health considerations
- None.
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.
- All examined cows showed signs of ophthalmitis, including: stromal keratitis, uveitis and retinitis
- Subacute-chronic MCF (5 cows examined):
- 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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Outcomes
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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.