The major clinical signs of chicken anemia virus (CAV) are characterized by anemia, thymus atrophy, yellow born marrow and immunosuppression. Since CAV is strongly resistant to most environmental factors, it is easily spreading among chicken flocks. Horizontal transmission likely occurs vial direct or indirect contact, such as oral and respiratory routes. Vertical transmission of virus through the eggs is considered to be the most important means of dissemination. Previous studies have shown that high titer of antibody could prevent virus shedding in the feces and protect chicken against CAV via vertical transmission. However, more recently, it was shown that CAV can be detected in gonads and embryos irrespectively from vaccined or unvaccinated breeders. During 2008-2009, several outbreaks of CAV occurred among layer chicks in Taiwan. It was interesting that most of chicks were the progeny of vaccined immune breeder flocks. The purpose of this study is to investigate if vertical transmission of CAV occurs currently in commercial chicks in Taiwan. The positive rate of CAV infection will be evaluated by using PCR and ELISA. Data obtained from this study may provide breeder farms to set up the vaccination program.
