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|Borna disease virus|
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The causative agent of Borna disease, Borna disease virus (BDV) is a neurotropic virus and is a member of the Bornaviridae family within the Mononegavirales order. Avian bornaviruses, a group of related viruses, have recently been identified as the cause of Proventricular Dilatation Disease, a disease of pet birds.
Although the Borna disease virus is mainly seen as the causative agent of borna disease in horses and other animals, recent findings have implicated that borna virus may play a role in some human neurological and psychiatric conditions including bipolar disorder and depression.
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. Note: BDV is not the cause of bipolar disorder, but it shows similar qualities to those found in bipolar disorder.
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.
Borna virus appears to have a wide host range, having been detected in horses, cattle, sheep, dogs and foxes. In 1995, the virus was isolated from cats suffering from a "staggering disease" in Sweden. Since that time, the virus has also been detected in cats in Japan and Britain.
Experimental infection of rats has been demonstrated to lead to learning impairments and altered social behaviour. The virus appears to be distributed primarily in the limbic system of the brain, including the hippocampus and entorhinal cortex. These areas of the brain are considered to be of importance in emotion.
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.
Borna disease in the horse gives rise to signs like:
- Unusual posture, gait and ear positions
- Movement Disturbances (principally ataxia or excess movement)
The first antibodies to Borna virus in humans were discovered in the mid-1980s. Since then, there have been conflicting results from various studies in regards to whether an association exists between the agent and clinical disease. Antibodies to Borna virus, which indicate prior infection, and Borna virus antigen have also been detected in blood donors.
Psychiatric diseaseEditJanice E. Clements and colleagues reported in the journal Science that antibodies to a protein encoded by the Borna virus genome are found in the blood of patients with behavioral disorders. In the early 1990s, researchers in Germany, America, and Japan conducted an investigation of 5000 patients with psychiatric disorders and 1000 controls, in which a significantly higher percentage of patients than controls were positive for BDV antibodies. Subsequent studies have also presented evidence for an association between Borna and human psychiatric disorders. However, not all researchers consider the link between Borna virus and human psychiatric disease to be conclusively proven. A recent study found no borna virus antibodies in 62 patients with the deficit form of schizophrenia.
Additional evidence for a role of Borna virus in psychiatric disorders comes from reports that the drug Amantadine, which is used to treat influenza infections, has had some success in treating depression and clearing Borna infection. Counter-claims state that Borna virus infections are not cleared by amantadine. The issue is further complicated by the fact that amantadine is also used in the treatment of Parkinson's Disease and may have direct effects on the nervous system.
- ↑ Ackermann A, Staeheli P, Schneider U (August 2007). Adaptation of Borna disease virus to new host species attributed to altered regulation of viral polymerase activity. J. Virol. 81 (15): 7933–40.
- ↑ 2.0 2.1 Bode L, Ludwig H (July 2003). Borna disease virus infection, a human mental-health risk. Clin. Microbiol. Rev. 16 (3): 534–45.
- ↑ 3.0 3.1 VandeWoude S, Richt JA, Zink MC, Rott R, Narayan O, Clements JE (November 1990). A borna virus cDNA encoding a protein recognized by antibodies in humans with behavioral diseases. Science 250 (4985): 1278–81.
- ↑ 4.0 4.1 4.2 Rott R, Herzog S, Bechter K, Frese K (1991). Borna disease, a possible hazard for man?. Archives of Virology 118 (3-4): 143–9.
- ↑ Dauphin G, Legay V, Pitel PH, Zientara S (2002). Borna disease: current knowledge and virus detection in France. Vet. Res. 33 (2): 127–38.
- ↑ Kamhieh S, Flower RL (June 2006). Borna disease virus (BDV) infection in cats. A concise review based on current knowledge. Vet Q 28 (2): 66–73.
- ↑ Miranda HC, Nunes SO, Calvo ES, Suzart S, Itano EN, Watanabe MA (January 2006). Detection of Borna disease virus p24 RNA in peripheral blood cells from Brazilian mood and psychotic disorder patients. J Affect Disord 90 (1): 43–7.
- ↑ Fukuda K, Takahashi K, Iwata Y, et al. (February 2001). Immunological and PCR analyses for Borna disease virus in psychiatric patients and blood donors in Japan. J. Clin. Microbiol. 39 (2): 419–29.
- ↑ Waltrip RW, Buchanan RW, Carpenter WT, et al. (February 1997). Borna disease virus antibodies and the deficit syndrome of schizophrenia. Schizophr. Res. 23 (3): 253–7.
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- ↑ Dietrich DE, Bode L, Spannhuth CW, et al. (March 2000). Amantadine in depressive patients with Borna disease virus (BDV) infection: an open trial. Bipolar Disord 2 (1): 65–70.