The isolation and characterization of chicken anemia agent (CAA) from broilers in the United States

A chicken anemia agent (CAA) isolated from commercial broilers in the United States was characterized in vivo and in vitro. When inoculated into susceptible 1-day-old chickens, the agent induced a severe bone marrow aplasia, thymic atrophy, multiple subcutaneous and intramuscular hemorrhages, and anemia, as evidenced by reduced hematocrits. Chickens derived from different breeder flocks and inoculated in ovo or at 1 day of age varied in their susceptibility to the CAA, with some flocks being highly susceptible, while others were almost totally resistant. This was true for both specific-pathogen-free and commercial chickens. The isolate was able to pass through a 50-nm-pore-size filter and was resistant to inactivation at 56 C for 30 minutes. It failed to agglutinate avian and mammalian erythrocytes and could not be propagated in conventional cell cultures. The physical and biological characteristics of the agent and the disease it induces indicate that it is similar to the CAA found in Japan and Europe.