Borna disease is an infectious neurological syndrome of warm-blooded animals, which causes abnormal behaviour and fatality. Originally identified in sheep and horses in Europe, it has since been found to occur in a wide range of warm-blooded animals including birds, cattle, cats and primates and has been found in animals in Europe, Asia, Africa and North America. The name is derived from the town of Borna in Saxony, Germany, which suffered an epidemic of the disease in horses in 1885.

Borna disease in sheep and horses arises after a four week incubation period followed by the development of immune-mediated meningitis and encephalomyelitis. Clinical manifestations vary but may include excited or depressed behaviour, ataxia, ocular disorders and abnormal posture and movement. Mortality rates are 80-100% in horses and greater than 50% in sheep.

The causative agent of Borna disease, Borna disease virus (BDV) is a neurotropic virus and is the sole member of the Bornaviridae family within the Mononegavirales order. It has the smallest genome (8.9 kilobases) of any Mononegavirales species and is unique within that order in its ability to replicate within the host cell nucleus.

The mode of transmission of BDV is unclear but probably occurs through intranasal exposure to contaminated saliva or nasal secretions. Following infection, individuals may develop Borna disease, or may remain subclinical, possibly acting as a carrier of the virus.

BDV also infects humans and is therefore considered to be a zoonotic agent. The role of BDV in human illness is controversial and it is yet to be established whether BDV causes any overt disease in humans. However, correlative evidence exists linking BDV infection with neuropsychiatric disorders such as bipolar disorder.

References

Koprowski, H. and Lipkin, W. I. (Eds) (1995). Borna disease. Springer-Verlag.