Humoral immune responses to chicken infectious anemia virus in three strains of chickens in a closed flock

This is a comparative study on seroconversion to chicken infectious anemia virus (CIAV) in a closed flock of specific-pathogen-free chickens undergoin g a natural outbreak and after vaccination of some of these flocks with a c ommercial, live vaccine. The N2a strain ((BB21)-B-21 haplotype) had the hig hest seroconversion after natural infection (94%) or vaccination (100%), fo llowed by the P2a strain ((BB19)-B-19) at 75%-82% seroconversion after natu ral infection and 85% seroconversion after vaccination. The S13 ((BB13)-B-1 3) chickens were 26% seropositive after natural infection and 75% seroposit ive after vaccination. N2a chickens with polymerase chain reaction (PCR)-po sitive tissues were 97% seropositive compared to 80%-83% PCR-positive and s eropositive for the P2a chickens and only 8% seropositive and PCR-positive for the S13 chickens. Seroconversion occurred at or near sexual maturity af ter natural infection in seven flocks studied.