Serological and Molecular Survey on Domestic Dog Hepadnavirus in Household Dogs, Italy

SIMPLE SUMMARY: Hepadnaviruses, similar to human hepatitis B virus (HBV), have recently been discovered in several mammalian species, including domestic carnivores. Circulation of hepadnaviruses in cats (domestic cat hepadnavirus, DCH) has been documented in a number of molecular surveys, demonstrating a worldwide distribution. In contrast, studies on hepadnavirus epidemiology in dogs are still limited. In this study, we screened an age-stratified collection of 600 canine sera for the presence of antibodies against the recombinant DCH core antigen (DCHCAg) and DCH surface antigen (DCHSAg). DCHC antibodies were found with an overall prevalence of 10.0% (60/600). Out of 60 positive serum samples, 30.0% (18/60) also possessed IgG anti-DCHSAg. All samples were also assessed molecularly using a pan-hepadnavirus nested-PCR and a DCH-specific quantitative PCR to investigate the presence of viral DNA, revealing a prevalence rate of 0.7% (4/600). Our results demonstrated unequivocally that hepadnaviruses genetically and antigenically related to DCH circulate actively in the canine population, albeit with a lower prevalence than in cats. ABSTRACT: The discovery of hepadnaviruses in cats (domestic cat hepadnavirus, DCH) and of a DCH-like virus in dogs has raised several questions regarding the role of these viruses in pets, with particular emphasis on their potential impact on animal health and epidemiology, as well as possible zoonotic implications. In this study, by screening an age-stratified collection of 600 canine serum samples for DCH with an ELISA assay based on the recombinant core antigen (DCHCAg), specific antibodies were found with an overall prevalence of 10.0% (60/600), with a higher prevalence in younger and older dogs. By retesting the canine DCHCAbs-positive sera with an ELISA test based on the recombinant surface protein of DCH (DCHSAg), a total of 18 sera (30%, 18/60) also contained IgG anti-DCHSAg. All the sera were also assessed molecularly using either a consensus hepadnavirus PCR or a specific real-time PCR for DCH. Hepadnavirus DNA was detected in four seronegative dogs, with a prevalence rate of 0.7% (4/600). On sequence analysis of the polymerase region amplified with pan-hepadnavirus primers, the amplicons displayed the highest nucleotide identity (97.3–99.6%) to DCH sequences detected in cats and to the domestic dog hepadnavirus recently identified in a canine serum sample from Italy.