Using Campylobacter hepaticus as an indicator organism to assess biosecurity on commercial egg farms

Spotty liver disease (SLD), caused by Campylobacter hepaticus (CH) has become an increasing problem in cage-free production in brown egg layers. Limited research exists monitoring the presence of CH in aviary style systems in the United States. This study was performed to investigate sources of CH in aviary style systems as a biosecurity indicator organism. A layer farm with two pullet and seven hen barns with a history of SLD was experiencing an outbreak in a 26-week-old single combed white Leghorns (SCWL) flock. Samples were collected from surfaces in employee areas and the production facilities, as well as insects and livers from pullets and hens, for a total of 214 unique samples. Samples were enriched for 48 h and struck onto brucella agar with 5% lysed horse blood and incubated microaerophilically for 72 h at 37 °C. Colonies from presumptive positive plates underwent DNA isolation and PCR analysis targeting the glycerol kinase and 16S rRNA genes. Livers from 6- and 12-week-old pullets (SCWL in both barns) were 90% positive for CH. Birds from all hen houses were 78% positive for CH, regardless of age or feather color. Birds in the barn exhibiting clinical symptoms and gross liver lesions were 80% positive for CH. All insects collected throughout the complex were positive for CH. Rodent stations were 75% and 93% positive in pullet and hen houses, respectively. Environmental samples from each barn were 77-100% positive for CH. Floor samples in restrooms, locker and break rooms were 100% positive at pullet facilities, but only 50% at hen facilities. Complex vehicle floor mats were 80% positive. These results suggest widespread contamination with CH; therefore, this bacterium may not be a viable biosecurity indicator organism on complexes with multiple flock ages. This is the first reported evidence of SLD in 6-week-old pullets. Next steps for this research should include further genomic characterization of CH and refined assessments of host-pathogen interactions.