Development of an enzyme-linked immunosorbent assay for the serological diagnosis of big liver and spleen disease.

An enzyme-linked immunosorbent assay (ELISA) was developed for the serological diagnosis of big liver and spleen (BLS) disease. The test utilizes a soluble, BLS-specific antigen that can be recovered from the livers of infected hens and that is known to react in the agar gel immunodiffusion (AGID) test. For use in ELISA, the BLS-specific antigen is fractionated by gel filtration chromatography and immobilized on microtiter plates using glutaraldehyde. The ELISA was evaluated using sera from infected and uninfected flocks originating in the United Kingdom and the United States. An ELISA format that incorporated control antigen recovered from the livers of uninfected birds for each serum tested was found to be more sensitive than the AGID test. A less sensitive but more cost-effective format that did not incorporate this control is considered suitable for large-scale flock screening programs.