Hepatitis viruses: prevalence of equine parvovirus-hepatitis virus and equine hepacivirus in France and Australia

Background: Recent identification of viruses considered responsible for Theiler’s disease (acute hepatitis) in horses include equine parvovirus-hepatitis (EqPV-H) and the most likely of several flaviviruses, equine hepacivirus (EqHV). Both of these viruses have now been detected in North America, Asia, and Europe. Objectives: To determine the prevalence of EqPV-H and EqHV in French and Australian horses and to analyse their respective phylogenetic relationships. Study design: Cross-sectional. Methods: Clinically documented sera from 188 Australian horses and 259 French horses collected between 2016-2019 were analysed. qPCRs validated according to the NF47-600 standard were used to detect EqPV-H and EqHV in sera. Sequencing for phylogenetic analysis was performed on two NS1 fragments (516 nt and 587 nt) for EqPV-H and one NS5B fragment (308 nt) for EqHV. A phylogenic network was built using a Median Joining Network algorithm. Results: 1) EqPV-H: 12/259 (4.6%) and 6/188 (3.2%) samples from French and Australian horses were positive, respectively. Viral loads ranged from 2.3e05 to 6.5e05 copies genome/ml. 2) EqHV: 5/259 (1.9%) and 21/188 (11.2%) samples from French and Australian horses were positive, respectively. Viral loads ranged from 6.1e04 to 1.4e08 copies genome/ml. Both EqPV-H (587 nt fragment) and EqHV phylogenetic analyses showed that Australian strains were clustered, while overall distribution was more heterogenous in French horses. Main limitations: The study population is built by accessing laboratory submissions and potentially biased. The 516 nt NS1 fragment could not be sequenced. Conclusions: This is the first report of EqPV-H detection in both Australian and French horses. The EqPV-H prevalence was similar between the two countries (p-value=0.6) although phylogenetic differences were observed between the two populations. This is also the first reported detection of EqHV in Australian horses, with a higher prevalence when compared with French horses.