Borna disease virus and the evidence for human pathogenicity: a systematic review

Background: Borna disease is a neurological viral disease of veterinary importance in central Europe, although Borna Disease virus (BDV) has been reported to be present in animals in most continents. The hypothesis that BDV is associated with human illness is controversial. However, should even a small fraction of mental illness be attributable to infection with BDV, this would be an important finding, not least because illness in that sub-population would, theoretically, be preventable. Methods: We systematically reviewed the evidence: that BDV infects humans; for the role of BDV in human neuropsychiatric illness; to assess the suitability of currently available laboratory methods for human epidemiological studies. Results: We identified 75 documents published before the end of January 2000, describing 50 human studies for BDV. There were five case studies and 44 (sero)prevalence studies, in a variety of patient groups. Nineteen prevalence studies (43%) investigated seroprevalence, 11 (25%) investigated viral prevalence and 14 (32%) investigated both. Seroprevalence ranged from 0% to 48%, and prevalence of virus or viral footprints from 0% to 82%. Discussion: Although agreed gold standard tests and evidence for test specificity are lacking, there is evidence that humans are exposed to the virus. Further epidemiological studies are required to establish whether there are associations with disease.