Frequent occurrence of nonprimate hepacivirus infections in Thoroughbred breeding horses - A cross-sectional study for the occurrence of infections and potential risk factors.

Recently, several new hepaciviruses have been identified of which the nonprimate hepacivirus (NPHV) - the closest relative to hepatitis C virus (HCV) discovered to date - is highly prevalent in horses. However, potential risk factors for the transmission of NPHV among horses remain still unknown. Therefore, the objective of this study was to investigate the occurrence of NPHV infections in Thoroughbreds in northern and western Germany and to identify potential risk factors associated with NPHV infections. Using a cross-sectional study design, a total of 733 serum samples from Thoroughbred broodmares and stallions from northern and western Germany were analyzed for the presence of anti-NPHV nonstructural protein 3 (NS3) antibodies and NPHV RNA using the luciferase immunoprecipitation system (LIPS) and a quantitative real-time PCR, respectively. Information regarding signalment, stud farm, breeding history and international transportation history of each horse were collected and evaluated. A frequent occurrence of NPHV was found in the study population with 453 seropositive horses (61.8%) and 134 horses (18.3%) carrying NPHV RNA. Furthermore, statistical analysis revealed that the probability of being infected decreased for horses with a transportation history with increasing age by 20% each year. For horses that stayed in Germany no association between age and infection could be observed. In conclusion, the high occurrence of NPHV infections in breeding Thoroughbreds suggests circulating NPHV infections, endemic herds or persistent shedding in these animals and revealed the association of age and international transportation as risk factor for NPHV infections.