Avian bornavirus or Parrot bornavirus has been isolated from the brains of parrots suffering from proventricular dilatation disease (PDD).
Borna disease virus exists world-wide in horses, sheep, cattle, cats, dogs, and ostriches. It is transmitted from animals to humans and between humans by infected saliva or other nasal mucosa secretions. This transmission through nasal, salival, or conjunctival secretions is currently assumed.
As documented in Germany and Australia, BDV is found in about one third (30%) of the adult population. The prevalence is about twice as high (60%) in children. Most of those infected (>80%) do not show any symptoms, and only 16-17% of those infected are predicted by some to form a mental illness during the course of his or her life. In the overall population, it is estimated that 5% is at an increased risk of becoming ill. Evidence of human BDV infection has been reported in the United States, Germany, and in other Eurasian continent, which includes Taiwan, Thailand, Iran and Japan.
Medical conditions associated with significantly higher rate of active Bornavirus infection are acute depressive episodes (uni- and bipolar), in 80-90% of patients, chronic obsessive-compulsive disorders (OCD), in at least 50-60% of patients, and chronic fatigue syndrome (CFS/ME0 in at least 40% of patients. The symptoms that are common to the majority of these patients are cognitive deficits and bradylogia (abnormally slow speech), reduced intellectual capability, attention and concentration deficits (especially among young adults and children), memory loss, and learning disabilities (especially among children and young adults).