Joy Tomlinson

Background Equine parvovirus hepatitis (EqPV‐H) is highly prevalent and causes subclinical to fatal hepatitis, which can occur in outbreaks. Whereas iatrogenic transmission is well documented, the mode of horizontal transmission is not known. The virus is shed in nasal, oral and fecal secretions, and PO transmission has been reported in a single horse. Hypothesis/Objective Investigate the efficiency of PO and nasal transmission of EqPV‐H in a larger cohort. Methods Prospective experimental transmission study. Eleven EqPV‐H‐negative horses were inoculated with 5 × 10 6 genome equivalents EqPV‐H. Serum PCR and serology for EqPV‐H were performed weekly and monthly, respectively. Horses first were inoculated PO, and then intranasally 8 weeks later. Results No horse became viremic or seroconverted within 8 weeks after PO inoculation. After intranasal inoculation, 5 horses became viremic within 6 to 12 weeks and seroconverted within 10 to 19 weeks. After a period without monitoring from 12 to 19 weeks postinoculation, another 5 horses were found to be viremic at 19 to 22 weeks. The second set of 5 horses could have been infected by horizontal transmission from the first 5 because of cohousing. Conclusions and Clinical Importance We demonstrated that EqPV‐H can be transmitted nasally. The prolonged eclipse phase before detectable viremia indicates biosecurity measures to control spread could be impractical.