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Neurology: Borna disease
Synonym(s): Near Eastern Equine Encephalitis (NEEE)
Introduction
- A rare, sporadic, severe neurological disease occurring in spring and early summer.
- Cause: Borna disease virus (BDV) - classified by itself in theBornaviridaefamily.
- Signs: abnormal mentation; compulsive behavior; circling; head pressing; depression; tremors; hyperesthesia; often progresses to convulsions or coma.
- Diagnosis: neurological examination; antibody testing of CSF and serum.
- Treatment: symptomatic care.
- Prognosis: grave high mortality; residual neurological deficits are common, necessitating euthanasia.
Presenting signs
- Subclinical encephalitis, peracute encephalitis through transient ataxia and fever all occur.
- Abnormal behavior.
- Neurological signs.
- Depression.
Acute presentation
- Behavioral and mentation changes.
- Signs of forebrain disease such as circlng, head-pressing, constant yawning, aggressiveness.
- Asymmetric vestibular signs and various cranial nerve functional deficits.
- Ataxia.
- Dysphagia.
- Hyperesthesia.
- Seizures.
- Coma.
Geographic incidence
- Europe and the Middle East.
- BDV-antibodies have been isolated from otherwise healthy horses in Israel, Japan and the USA, although the disease has not been recorded there.
Public health considerations
- Cases in humans, sheep, cattle, goats, ostriches, rabbits and cats have been documented.
Cost considerations
- Treatment is often unsuccessful.
- Successful treatment is often prolonged and residual deficiencies are common, resulting in euthanasia several months down the line.
Pathogenesis
Etiology
- Caused by Borna disease virus (BDV).
- Cell-free virus has still to be isolated for full virology to be possible.
- Route of infection is unknown - ? inhalation, ingestion, tick-borne.
Pathophysiology
- Low morbidity.
- The specific etiology of the development of the clinical disease is unknown, but thought to be the result of a virus-induced, cell-mediated, immunopathological reaction.
- The virus can produce latent or persistent infections, or asymptomatic carrier states which may excrete the virus and be a potential risk to others.
- High mortality around 80%.
Timecourse
- A long incubation period of 4 weeks to 6 months before clinical signs.
- Acute encephalitis phase usually lasts 1-3 weeks.
- Full recovery is rare.
Epidemiology
- Route of infection is unknown - ? inhalation, ingestion or tick-borne.
- Cases are usually sporadic.
- In-contacts or recovered animals may become asymptomatic carriers which can excrete the virus indefinitely.
- ? Wild birds are implicated in transmission of the disease between populations.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Priestnall S L et al (2011) Borna disease virus infection of a horse in Great Britain. Vet Rec 168 (14), 380 PubMed.