How Effective are Environmental Sampling Methods in Detecting Pathogens in Cage-Free Aviaries?
Researchers from the USDA Agricultural Research Service and Purdue University conducted an experiment at the Purdue Animal Sciences Research and Education Center (ASREC) Poultry Unit to evaluate different environmental sampling methods for detecting pathogens in cage-free aviary housing systems over time. They collected swabs between August and December from five locations - concrete dust, drag swabs, egg belt dust, manure belt scrapers, and wall dust. The samples were tested for Listeria, Campylobacter, and Salmonella.
Which Sampling Methods Are Most Effective for Detecting Listeria and Campylobacter?
The detection rate of Listeria was highest in drag swabs (75%) and manure scrapers (50%). Over 90% of Listeria recovered was L. innocua, not the pathogenic L. monocytogenes. Campylobacter detection was highest in concrete dust (96.25%) likely due to rodent excreta. After concrete dust, manure scrapers (73.75%) and drag swabs (49.37%) were still most effective. Drag swabs and manure belt scrapers appear to be the best methods for detecting Listeria and Campylobacter.
How Does Pathogen Detection Change Over Time?
Listeria detection peaked at 70% when hens were 22 weeks old, decreasing over time as the birds’ intestinal microbiota developed. Campylobacter followed a similar trend, with highest detection at 22 weeks, remaining higher through 30 weeks before dropping. Seasonality may explain higher summer/fall rates. For both pathogens, scrapers and drag swabs showed fluctuating but more consistent detection rates over time relative to other methods.
What About Salmonella Detection Following Inoculation?
No naturally occurring Salmonella was found. Researchers introduced low doses of nalidixic acid-resistant Salmonella Enteritidis (SE) into duplicates of each sample type to test detection. Recovery rates were very low at first but rose dramatically by later sampling times (34-39 weeks). The FDA requires SE sampling of layer hen environments at 40-45 weeks, which matched when inoculated SE was best recovered in this study.
In this controlled experiment, drag swabs and manure scrapers were overall most effective for pathogen detection. Discovery of pathogens decreased with hen age but still fluctuated depending on sampling method. Targeted sampling protocols like the FDA Egg Rule appear well suited to conventional and cage-free housing systems based on when experimentally introduced SE was recoverable. Further research oninteractions between pathogens detected together may improve environmental sampling strategies.
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References
Environmental sampling methods’ influence on detection of pathogens in cage-free aviary housing
