Seroprevalence of Newly Discovered Duck Flavivirus in Farm Animals

Abstract

New flavivirus has recently emerged in domestic ducks in China. The virus, provisionally designated duck flavivirus (DFV), causes highly significant economic losses to duck industry in China as a result of reduction in duck meat and eggs. Little is known about the epidemiology of this new viral disease. In this study, we developed a fluorescence-based microneutralization assay to evaluate the seroprevalence of neutralizing antibodies to DFV in domestic farm animals as well as to assess antibody responses in ducks receiving an inactivated DFV vaccine. Screening of duck and pig serum samples found that 54.7% and 1.2%, respectively, of individuals had measurable neutralizing antibody titers to DFV. Interestingly, no serologic evidence of chicken infection was found in a collection of 356 chicken sera from farms where outbreaks of DFV infection among ducks were documented. Thus, results of our serological survey demonstrated for the first time that DFV has a limited host range and duck appears to be the primary host. Furthermore, we showed that a significant portion of vaccinated ducks (approximately 26.7%) had weak or no detectable antibody titers to DFV. The observed suboptimal antibody response in some of vaccinated ducks may help to explain recurring disease outbreaks in duck farms in China, although the region-wide vaccination program has been implemented.