The focus of this article is an uncommon condition that we diagnosed over the winter on the Somerset Levels, in the North of the practice.
Malignant Catarrhal Fever, MCF, is a fatal disease of cattle. Affected animals are usually very depressed, with a high fever (>40ºC), profuse nasal discharge, eye lesions (usually seen as a blue discolouration and swelling of the eyes), and crusting, particularly around the nose and sometimes teats. Other signs might include blood in the urine and faeces, and in some cases the animal may seizure.
Unfortunately there is very little we can do about this disease with regards to treatment or prevention, as there is no specific therapy or vaccination available. Due to the severity of clinical signs, euthanasia of affected cattle is our only option. We strongly advise any suspicious cases are examined by a vet, and a blood test taken to confirm the diagnosis.
What we do know about MCF is that it is caused by a virus carried by sheep (Ovine Herpesvirus 2), and less commonly goats. When a sheep becomes infected they become carriers of the virus for life but show no obvious signs. Lambs are usually infected at a young age from other individuals in the flock and typically start to shed the virus when they are around 6-9 months old, with adults shedding at a much lower rate.
Transmission from sheep to cattle is normally from nasal discharge and direct contact. Because of this, advice normally centres around keeping cattle away from sheep, particularly lambs, which may reduce the risk of cattle catching the virus. Unfortunately this is sometimes not enough, with transmission possible by airborne routes and has been demonstrated at distances of at least 70 metres. Once cattle catch the virus, the incubation period is highly variable, and in some cases can take over 200 days before any clinical signs occur which makes it almost impossible to identify when transmission occurred.
Other noteworthy points are that:
Affected cattle do not usually transmit the virus to other cattle so if a case is found this does not pose a significant risk to the remainder of the herd.
Outbreaks are not common, and usually only isolated cases are identified, not large numbers of animals.
It is rare! We have only had five cases confirmed across the practice in the last 12 months.
Please remain vigilant. Once again, we would strongly recommend calling in for any suspect cases for animal welfare reasons and to confirm the diagnosis.
Written By Tom Angel, Veterinary Surgeon
