Field Basis Evaluation of Eimeria necatrix-Specific Enzyme-Linked Immunosorbent Assay (ELISA) for Its Utility in Detecting Antibodies Elicited by Vaccination in Chickens

Eimeria necatrix-specific ELISA, using a recombinant antigen (the cDNA-clone NP19 expressing protein), was utilized to detect antibodies against E. necatrix in breeder pullet flocks that had previously received an attenuated live vaccine to E. necatrix. Vaccinated flocks were discriminated significantly from non-vaccinated flocks by their antibody titers and antibody positive rates at 30-55 days post-vaccination. In addition, E. necatrix-oocysts were confirmed in fecal samples of vaccinated flocks using PCR in the case where the antibody positive rates rose. These findings implied that the vaccination prompted repeated infections, and consequently the chickens generated antibodies and secured their protection against virulent field-E. necatrix. Therefore, the ELISA was suggested to be a useful tool to estimate the immune state of chickens as a result of vaccination with a live E. necatrix-vaccine.