Bovine Herpesvirus 5
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Caused By: BHV-5 — Bovine Encephalitis Virus — Bovine Encephalitis Herpesvirus
The virus is very similar to BHV-1, which is responsible for the major bovine disease, IBR. Although BHV-1 can cause neurological signs, BHV-5 demonstrates increased neurotropism.
South America, USA, Australia, Germany and Hungary.
Young calves up to ten months old are most commonly affected. Nervous disease is usually acute.
BHV-5 causes tachycardia and tachypnoea with pyrexia, dyspnoea, mucoid nasal discharge, gasping and abnormal lung sounds. Infected animals often hypersalivate and abdominal pain may be observed.
Affected animals are also often generally lethargic, anorexic, display various signs of pain and discomfort and may be recumbent.
Signs of acute neurological infection include opisthotonus, hyperaesthesia, dullness, abnormal behaviour, ataxia, head tilt, head pressing, conjunctivitis, blindness, coma and seizures. Proprioceptive deficits may also develop suddenly and acutely. Disease in neonatal animals causes rapid generalised viraemia and sudden death.
Subacute disease causes calves to be depressed, anorexic and ataxic and suppresses rumenal motility. The dyspnoea is more pronounced than in acute infection due to the longer disease course and is almost always fatal. Those that recover become latent carriers.
Calves that acquire infection after vaccination for BHV-1 and those that have been previously infected by either virus become silently infected and the virus becomes latent. Sites of latency include the trigeminal ganglia of the CNS and mucosae of the nose and trachea. The virus can then recrudesce with stress and/or immunosuppression, but usually produces no clinical signs; it is however shed into the nasal secretions providing a source of infection.
Specific monoclonal antibodies are available for BHV-5 and can be used with immunoperoxidase staining on formalin fixed brain tissue for confirmatory identification. PCR is also available.
On post-mortem examination, a non-suppurative meningoencephalitis and evident perivascular cuffing. Lesions are more pronounced in white matter. Necrosis, oedema and spongiosis may also be recognisable. In some cases, satellitosis also develops.
There is no treatment for infected individuals.
No vaccination is available for BHV-5 but some cross-protection appears to be granted from some BHV-1 vaccines. This needs to be proven for each available vaccine.
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This article has been expert reviewed by Nick Lyons MA VetMB CertCHP MRCVS
Date reviewed: 31 August 2011
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