Pathogenesis of NGPV and DuCV CO-infection pathogenicity analysis of co-infection with novel goose parvovirus and duck circovirus in Cherry Valley meat ducks.

The prevalence of short beak and dwarfism syndrome (SBDS) in China is increasing, causing much economic losses to the waterfowl industry. Novel goose parvovirus (NGPV) has been identified as the primary pathogen; however, it is difficult to reproduce SBDS with NGPV infection alone. Duck circovirus (DuCV) orchestrates immunosuppression in ducks, rendering them more prone to other pathogenic infection. Notably, a high co-infection rate between DuCV and NGPV has been observed. Given this context, the present study utilized the Cherry Valley meat duck, the largest breed in China, as the experimental model. In this study, ducks were separately or co-infected with NGPV and DuCV. At 1, 3, 7, 14, 21, 28, and 35 days post-infection (DPI), six ducks were randomly selected to detect relevant indicators and evaluate whether the two viruses have a synergistic pathogenic effect. The results showed that these two viruses were continuously detected in serum and swabs in the co-infection group from 1 DPI onward, and were higher than those in the corresponding single-infection group. The co-infected ducks exhibited symptoms of SBDS. The levels of calcium, phosphorus, and lymphocytes were significantly reduced, whereas the level of total bilirubin was significantly elevated, indicating impaired metabolic and immune functions. Moreover, compared with single-infection groups, ducks in the co-infection group exhibited more severe immunosuppression and tissue damage, along with higher viral loads of these two viruses in many organs. The results showed that co-infection with DuCV and NGPV can promote viral replication, increase pathogenicity, and lead to the occurrence of SBDS. This study will provide a theoretical basis for the prevention and control of SBDS.