B114 - MALIGNANT CATARRHAL FEVER

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B114 - MALIGNANT CATARRHAL FEVER

Nature of the disease
Malignant Catharral Fever (MCF) is an acute disease of Bovine and Cervidae due to infection by alcephaline hepesvirus (AHV-1) or ovine herpesvirus-2 (OvHV-2).. The disease, characterised by an important fever, is sporadic and causes high mortality. 
Classification
OIE, List B disease
Susceptible species
Bovine, water Buffalo, domestic deer and many wild ruminants, rarely pigs can be infected.
Distribution
MCF is ubiquitous but it is particularly present in Africa. In the Pacific region, it is reported present in Australia and in New Zealand.
Clinical signs 
The incubation period is unknown. The acute form is called "Head and eyes" form and include:  
  • High fever (40-42°C) and anorexia
  • Weakness, 
  • Erosion of the buccal mucosa,
  • Adenopathy,
  • Purulent nasal discharge,
  • Dyspnoea,
  • Keratoconjonctivitis with progressive opacity of the cornea and ophtalmia
  • Encephalitis with neurological disorders
  • Death within 2 weeks in 90% of the cases

The peracute form is called the intestinal form, it is marked by a liquid and haemorrhagic diarrhoea. The ophthalmic signs are milder and the death occurs in 1-3 days.

Post-mortem findings 
  • Haemorrhage and erythema in the mouth, nasal cavities and pharynx,
  • Erosion of the tip of the cheek papillae,
  • Longitudinal shallow erosions on the oesophagus,
  • Liver is swollen,
  • Petechiae in the brain and meninges.
Differential diagnosis 
  • Bovine Virus Diarrhoea/Mucosal Disease,
  • IBR/IPV,
  • Rinderpest,
  • Pneumonic pasteurellosis,
  • Photosensitive dermatitis
Specimens required for diagnosis 
Specimens of spleen, lung, lymph nodes, adrenals or 10 mL of blood on EDTA, cooled but not frozen, can be submitted for virus isolation, PCR or fluorescence and immunocytochemical tests.

Brain, cephalic lymph nodes, and possibly spleen, kidneys and intestines can be submitted fresh, frozen or fixed in paraffin for histology.

Serological tests include immunofluorescence, immunoperoxidase and ELISA tests, but the antibody response of clinically affected animals is limited.

Transmission   
The AHV-1 is usually shed by wild Ruminants and the OvHV-2 by sheep without clinical signs. Transmission to cattle or other susceptible species may occur by inhalation of cell-free virus in infectious aerosol droplets, ingestion of feed or water contaminated with infectious secretions or faces, or possibly mechanically by arthropods.   
Risk of introduction   
The viruses can be introduced by importation of infected cattle or deer, or more probably by infected unapparent reservoir such as sheep or wild species for zoo. 
Control / vaccines  
There is no vaccine. Control requires segregating natural hosts from susceptible species. Contaminated flocks remain dangerous for years and should be culled.
References
  • Malignant Catharral Fever, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 533-536
  • Malignant Catharral Fever, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 889-893
  • Office International des Epizooties, 2002
  • Office Vétérinaire Fédéral Suisse