The Borna disease virus (BDV) is caused by an infectious agent — a negative-sense, single-stranded RNA virus. First discovered in European horses and sheep, BDV infects the nervous system of many animal species — including primates and birds. BDV is named after the town of Borna in Saxony, Germany, where an epidemic of infectious encephalitis caused a large number of equine deaths in 1885 (Carbone, 2001).
The Borna disease virus can induce behavioral symptoms in animals, such as anxiety, aggression, cognitive defects, and hyperactivity (Bautista et al., 1994; Dittrich et al, 1989). But it does so without any obvious physiological or typical disease signs, such as fever, sickness, or a decreased level of consciousness.
What behavioral signs do exist tend to include “hyperactivity, hyperreactivity, and aggression and subsequently as a rapidly progressive, often fatal, neurological impairment, including seizures, ataxia, and paraplegia” (Carbone, 2001). Animals with BDV also commonly exhibit serious problems in social behavior — such as play — as well as chronic anxiety (Hornig et al., 1999; Pletnikov et al., 1999).
For decades after its discovery, it was impossible to test for BDV in humans, so it wasn’t possible to determine whether BDV might be the cause of specific behavioral symptoms or even mental disorders. During this time, some researchers theorized that BDV might be responsible for certain human behavioral symptoms and cognitive deficits — symptoms found in mental disorder such as schizophrenia, bipolar disorder, and depression. For instance, speculative research conducted by VandeWoude et al. (1990) found antibodies to a protein encoded by the BDV genome in the blood of three of seven patients who had behavioral disorders.
Depression, Mood, Schizophrenia & Borna Virus
Once genetic testing became less expensive and more widely available, researchers discovered ways to reliably test for the presence of BDV genetic material and antibodies to BDV in humans. This made more detailed human-subjects research into the impact of the Borna disease virus possible.
In 2012, researchers conducted what’s now considered a gold-standard for investigating links between viral infection and human disease. This research was a blinded, case-controlled scientific study to examine the connection between BDV and three specific kinds of mental illness: schizophrenia, bipolar disorder, and clinical depression (Hornig et al., 2012). The study examined 198 adult patients who were diagnosed with one of these disorders, and matched them to 198 healthy control adults who had no history of disease or mental illness.
The scientists then tested each person for the presence of BDV in blood samples at the onset and 6 weeks after an acute psychiatric episode. They found no evidence of active or historical infection with BDV in any of the subjects.
This study closes the door on the relationship between BDV and mental illness in humans. There is no apparent connection between the Borna Disease Virus and schizophrenia, bipolar disorder, or depression.
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