Pathogenicity of duck circovirus and novel goose parvovirus co-infection in SPF ducks.

Duck circovirus (DuCV) is one of the most prevalent infectious viruses in the duck industry in China. Although the clinical signs vary, it often causes immunosuppression in the host and leads to secondary infection with other pathogens. Novel goose parvovirus (NGPV) mainly infects ducks and causes short beak and dwarfism syndrome in ducks. However, the incidence of infection in ducks has increased in recent years, and the phenomenon of mixed infection with DuCV is common, resulting in more severe clinical morbidity. However, there are no systematic studies evaluating the presence of mixed infections. In order to investigate the synergistic pathogenicity of DuCV and NGPV co-infection in SPF ducks, a comparative experiment using DuCV and NGPV co-infection and mono-infection bird models was established. The results showed that the clinical signs of short beak, dwarfism and immunosuppression were more obvious in DuCV and NGPV co-infected ducks; the tissue damage of target organs was more serious, and the viral titre in organs and cloacal swabs were more significant compared with those of SPF ducks infected with only one virus. The results indicated that co-infection with DuCV and NGPV could promote viral replication and cause more severe tissue damage and immunosuppression than single virus infection. The present study reveals that the co-infection of NGPV and DuCV has a synergistic pathogenic effect from the aspect of pathogenicity, and the conclusions drawn not only clarify the direction of the subsequent research on the mechanism of co-infection of NGPV and DuCV, but also provide a scientific basis for the research on the co-infection of immunosuppressive pathogens and other pathogens.