Chickens on 14 broiler breeder farms were examined at various times throughout their laying cycle. Antibodies to the turkey rhinotracheitis virus were common although they were not always accompanied by clinical signs of the swollen head syndrome. Ninety-nine broiler flocks were tested of which only 20 were serologically positive to the virus. Some of these infections were subclinical. On nine farms where swollen head syndrome occurred several successive flocks were sampled; the syndrome occurred intermittently.
Outbreaks of clinical chicken anaemia in four broiler chicken flocks affected chicks which were all the progeny of the same parent flock. Three of the flocks were reared on farms in the south-east of England and in these flocks clinical disease did not occur in other chicks of the same age. The fourth flock was reared in a positive-pressure isolator and clinical disease appeared at 10 days of age. Chicken anaemia agent was isolated from three of the flocks. The clinical signs, post mortem lesions and histopathological changes were similar to those reported in outbreaks of the disease in other countries. The parent flock seroconverted to chicken anaemia agent, as determined by fluorescent antibody tests, during the course of the outbreaks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.