Persistence of maternal antibody to chicken anaemia agent and its effect on the susceptibility of young chickens.

Based on the incidence of anaemia, chicks derived from immune dams were shown to resist the parenteral challenge with chicken anaemia agent (CAA) until 14 days of age. Judging from thymic atrophy induced by the CAA-challenge, maternally-derived immunity of chicks against CAA infection persisted up to at least day 21. A very low level of maternal anti-CAA antibody seemed to be efficacious to the CAA-challenge. These results are discussed in relation to the significance of CAA anaemia under field conditions.