Pathogenesis of duck circovirus genotype 1 in experimentally infected Pekin ducks.

Ducks infected with duck circovirus (DuCV) exhibit feathering disorder, growth retardation, and low body weight. The virus can induce immunosuppression and increase rates of infection caused by other pathogens. The purpose of the present study was to investigate the pathogenesis of DuCV in experimentally infected Pekin ducks. At postmortem examination, gross lesions were observed in the immune organs including bursa of Fabricius (BF), thymus, and spleen. Hemorrhage, lymphocytic depletion, necrosis, and degeneration were observed in the bursal tissues by histological examination. The TUNEL assay was performed with bursal tissue. There was a significant difference of the apoptosis rate between the negative and DuCV-infected ducks. The earliest time point for detection of DuCV DNA in sera, cloacal swabs, and organs was 1 wk post-infection (WPI). Viral shedding was persistent and detectable at the end of the experiment (10 WPI). The findings provide evidence that horizontal transmission and persistent infection are the characteristics of DuCV. The organ with the highest mean viral load was the spleen, followed by BF, cecal tonsil, lung, thymus, liver, and kidney. We successfully established an experimental DuCV genotype 1 (DuCV-1) infection in Pekin ducks and demonstrated the pathogenicity and persistence of DuCV-1. In conclusion, DuCV-1 caused extensive damage to the immune organs that may have resulted in immunosuppression. Pathobiological characteristics of DuCV-1 include systemic infection, persistent infection, and horizontal transmission. These features allow DuCV-1 to circulate more easily in farms and increase the susceptibility of ducks to other diseases.