Malignant catarrhal fever
Two strains of MCF virus have been recognised, Ovine herpesvirus 2 (OvHV-2) and Alcelaphine herpesvirus 1 (AlHV-1), which are endemic in sheep and goats and is transmitted from healthy carriers to cattle, presumably by oral transmission of virus.
The virus is transmitted by nasal secretions and results in lifelong infections and death in cattle. The prevalence of infection in cattle seems not to be influenced either by their age or the degree of contact with the sheep and goats.
In some subclinical cases, the only signs observed are chronic alopecia and weight loss.
During outbreaks, affected cattle present with anorexia, signs of depression, diarrhea, fever and respiratory distress ultimately leading to death. Catarrhal inflammation of mucous membranes is pathognomonic. Lymphadenopathy and neurological signs are also observed in severe cases.
Diagnosis is based on presenting clinical signs, postmortem findings on cattle which have died, supported by laboratory examination of diseased tissue.
Although many cattle do not succumb to the viral infection, recovery is slow and invariably most cases are fatal.
A vaccine is currently available which shows promise at minimising outbreak.
Current control measures for MCF rely on minimizing contact between carrier animals and susceptible livestock.
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