Bovine malignant catarrhal fever

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 unapparent 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. In Southern Africa the disease is known as snotsiekte, from the Afrikaans. BMCF is an important disease where reservoir and susceptible animals mix. There is a particular problem with Bali cattle in Indonesia, bison in the US 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 David's 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, inappetence and diarrhea. Some animals have neurologic signs, such as ataxia, nystagmus, and head pressing. Animals that become infected with the virus can become extremely sensitive to touch, especially around the head. It is also possible that become aggressive and charge at approaching animals and people. If the virus continues untreated, seizures could develop. Affected animal usually die five to ten days of the first signs of clinical signs. Once the cow shows clinical signs there is no chance of recovering. 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. There are many factors that can increase the chances of infection or affect the severity of an outbreak. The amount of animals in the herd, population density and species of the susceptible hosts are huge factors. Other factors include closeness of contact and amount of virus available for transmission.