The infection is widespread in broiler and replacement parent and laying-strain pullets. 10.3 Transmission Both vertical and horizontal routes of infection occur under commercial conditions. Contaminated live vaccines prepared from infected embryos were previously responsible for widespread dissemination of infection. 10.4 Clinical Signs Morbidity is variable, with onset at 10 days. Primary CA mortality occurs during the 15-20 day period.
Affected chicks are pale and stunted.
10.5 Pathology Thymus and bone marrow atrophy and muscular hemorrhages are characteristic. Septicemia and gangrenous dermatitis occur in older birds, following secondary bacterial infection. 10.7 Prevention Immunization of young breeders with attenuated vaccine. Biosecurity to prevent horizontal infection. Appropriate management procedures can reduce the effects of primary CA infection.