Pilot Serological and Molecular Surveys of Borna Disease Virus Infection of Domestic Cats

Pilot serological and molecular diagnostic studies were undertaken on retrospective and prospective samples of plasma and PBMCs of domestic cats obtained from the William R. Pritchard Veterinary Medical Teaching Hospital at the University of California, Davis, and the Specialized Infectious Diseases Lab at the Veterinary Teaching Hospital, Colodrado State University, to assess this species for previous exposure and/or current infection with Borna Disease virus (BDV), in order to draw conclusions about the existence of Bornaviruses in the United States. Exploratory serological assessment of a convenience serum sample of cats seen at the VMTH-UC Davis, revealed circulating antibodies to Bornavirus antigens in 11 of 301 (3.7%) domestic cats tested by dual-labeling immunofluorescence (IFA) assay, optimized for enhanced specificity. An Indirect screening ELISA based on 2 recombinant BDV antigens (p24 and p40), on the other hand demonstrated low agreement (23.2%), limiting the diagnostic utility of the ELISA, in contrast with the highly specific dual-IFA. These dual-label IFA results represent the first report of seroreactivity to BDV antigens in domestic cats in North America, in the absence of overt neurological disease. Serological assessment of a stratified sample of 384 sera obtained from different geographical regions of the U.S., revealed a 2.3% seroprevalence of circulating antibodies to BDV antigens in 9 of 384 sera, by dual-label IFA, while 15 of 384 (3.9%) sera were reactive to BDVp24 and p40 recombinant proteins by the Luminex screen. In a second subgroup of 405 cat sera categorized by CNS disease status, the dual-IFA scored 15 of 405 (3.7%) sera reactive to BDV antigens, while 7 of 405 (1.7%) sera were reactive by the recombinant Luminex screen. We observed a high correlation in reactivity to BDV recombinants, and reactivity to an irrelevant recombinant protein (SPV VP2), leading to the suspicion that the observed Luminex seroreactivity was spurious. Given the inherent high specificity of the dual-IFA, we conclude that BDVs circulate at a prevalence of 2.3% in the U.S., basing on regionalized stratified sampling, as assessed by the dual-IFA assay. We were unable to make conclusions about relationships between reactivity to BDV and provenance, or CNS disease status, as these data were unavailable. Prospective molecular and serologic studies conducted on 462 samples of domestic cats seen at the VMTH-UC Davis revealed circulating antibodies to BDV-specific antigens in 19 sera (4.1%), but no detectable BDV genomes in paired PBMC samples, by conserved and degenerate probe and primer Bornavirus-specific real time PCR assays. Follow up case-based retrospective and prospective studies are recommended to comprehensively investigate CNS disease of undetermined etiology in domestic cats, for which the common differential diagnoses have been excluded, for potential BDV infection.