Reflection of serum immunoglobulin isotypes in the egg yolk of laying hens immunized with enterotoxigenic Escherichia coli

Aim: The aim was to study the seroconversion and development of egg yolk immunoglobulins in adult laying White Leghorn hens immunized against an isolate of enterotoxigenic Escherichia coli (ETEC) bearing K91 and K88ac antigens, obtained from diarrheic piglet. Materials and Methods: Adult laying White Leghorn hens were immunized with inactivated enterotoxic E. coli strain isolated originally from a case of piglet diarrhea following recommended schedule. The development of whole antibodies and isotype-specific antibodies in serum and egg yolk were measured using indirect enzyme-linked immunosorbent assay (ELISA). Piglets suffering from diarrhea with fecal samples positive for ETEC were fed with egg yolk and compared with diarrheic control group. Results: The serum and egg yolk ELISA antibody titer against E. coli strain used in the present study was as high as 2666.66±307.92 and 933.33±203.67 respectively on 50 day-post-vaccination (DPV). The immunoglobulin Y (IgY) was the predominant isotype in serum and egg yolk, which reached the peak titer of 2200±519.61 in serum on 40 DPV and 800±244.94 in egg yolk on 50 DPV. IgM titer in serum and egg yolk was found to be meager, and no IgA could be detected. Diarrheic piglets fed with the egg yolk suspension from immunized hens showed a promising result in controlling diarrhea. Conclusion: Egg yolk antibodies are considered a suitable immunotherapeutic alternative to conventional antibiotic therapy. High titer of egg yolk antibodies raised in the immunized hen against an isolate of ETEC holds the potential to be used for passive protection of diarrheic piglets during their most susceptible period of infection.