Environmental sampling methods' influence on detection of pathogens in cage-free aviary housing

The environmental sampling of layer housing systems is essential to identifying potential pathogens that are of concern to human health. To identify the natural occurrence of pathogens (Listeria, Campylobacter, and Salmonella) at various locations in a cage-free aviary housing system, swabs were collected when hens were 22 to 39 wks of age. Duplicate environmental swabs were taken and inoculated with a low dose (10¹ cfu) Salmonella Enteritidis (SE) and examined for the recovery of SE from environmental samples. Detection of Listeria (P < 0.0001) and Campylobacter (P < 0.0001) varied between the environmental sample types taken: concrete dust, drag swabs, egg belt dust, manure belt scraper swabs, and wall dust. Detection of Listeria (P < 0.0001) was the highest (70.0%) at the beginning of the study (22 wk) and decreased over time. Detection of Campylobacter (P < 0.001) was also the highest at 22 wk, however the decrease over time was more gradual. Interestingly, detection of Campylobacter (P < 0.0001) was the greatest in concrete dust samples (96.25%), which can be attributed to the presence of rodent excreta in the samples. Drag swabs and manure belt scraper swabs were the best sampling types for high detection of Listeria and Campylobacter. It should be noted that Listeria recovered was not of human health concern. No naturally occurring Salmonella was identified in this study. The recovery of the SE inoculum increased over time, reaching the greatest recovery in drag (81.25%; P < 0.0001), egg belt dust (100.00%; P < 0.0001) and wall dust swabs (100.00%; P < 0.0001) by 39 wk. This high rate of SE recovery occurred just before US mandatory SE environmental monitoring at 40 to 45 wks of age. Based on this study, the use of drag and manure belt scraper swabs are effective in detecting Listeria and Campylobacter in cage-free aviary housing. Along with good pest management, the occurrence of pathogens could be monitored and reduced in laying hen flocks.