Application of flagella-based immunoassays for serologic detection of Salmonella pullorum infection in chickens

Occasional Salmonella pullorum outbreaks still occur in commercial poultry flocks despite widespread serologic testing, raising concerns about the efficacy of standard agglutination-based serologic assays for detecting infections with current field strains. The recent observation that many S. pullorum strains are recognized by antibodies to certain Salmonella flagellar proteins suggests that similar antibodies might be elicited in infected birds. In the present study, flagella-based enzyme immunoassays were developed and applied to detect antibodies in hens experimentally infected with recent S. pullorum isolates. Antibodies were detected in 29%-44% of serum samples from orally inoculated hens by two flagella-based immunoassays. Similar frequencies of positive results (33%-41%) were obtained by applying two standard agglutination-based tests for antibodies to S. pullorum. Antibodies to flagellar antigens, if also present in naturally infected chickens, could provide an alternative method for detecting S. pullorum infection in poultry flocks.