Bovine malignant catarrhal fever
| Bovine malignant catarrhal fever | |
|---|---|
| Virus classification | |
| Group: | Group I (dsDNA) |
| Family: | Herpesviridae |
| Genus: | Macavirus |
| Species: | Alcelaphine gammaherpesvirus 1 (AlHV-1) Ovine gammaherpesvirus 2 (OHV-2) |
Bovine malignant catarrhal fever (BMCF) is a fatal lymphoproliferative disease caused by a group of ruminant gamma herpes viruses including Alcelaphine gammaherpesvirus 1 (AlHV-1) and Ovine gammaherpesvirus 2 (OvHV-2) These viruses cause inapparent infection in their reservoir hosts, (sheep with OvHV-2 and wildebeest with AlHV-1) but are usually fatal in cattle and other ungulates such as deer, antelope, and buffalo.
BMCF is an important disease where reservoir and susceptible animals mix. There is a particular problem with Bali cattle in Indonesia, bison in the USA and in pastoralist herds in Eastern and Southern Africa.
Disease outbreaks in cattle are usually sporadic although infection of up to 40% of a herd has been reported. The reasons for this are unknown. Some species appear to be particularly susceptible, for example Pére Davids deer, Bali cattle and bison, with many deer dying within 48 hours of the appearance of the first symptoms and bison within three days. In contrast, post infection cattle will usually survive a week or more.
The term bovine malignant catarrhal fever has been applied to three different patterns of disease:
The incubation period of BMCF is not known, however intranasal challenge with AHV-1 induced MCF in one hundred percent of challenged cattle between 2.5 and 6 weeks. Shedding of the virus is greater from 6–9 month old lambs than from adults. After experimental infection of sheep, there is limited viral replication in nasal cavity in the first 24 hours after infection, followed by later viral replication in other tissues.
The most common form of the disease is the head and eye form. Typical symptoms of this form include fever, depression, discharge from the eyes and nose, lesions of the buccal cavity and muzzle, swelling of the lymph nodes, opacity of the corneas leading to blindness, inappetance and diarrhea. Some animals have neurologic signs, such as ataxia, nystagmus, and head pressing. Peracute, alimentary and cutaneous clinical disease patterns have also been described. Death usually occurs within ten days. The mortality rate in symptomatic animals is 90 to 100 percent. Treatment is supportive only.
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