Prevalence, risk factors, and human health implications of Salmonella enterica and Campylobacter spp. in Vermont backyard poultry

Authors: PATCH, CHELSEY - University Of Vermont; LARSEN, KATALIN - University Of Vermont; Armstrong, Cheryl; Kanrar, Siddhartha; MICHAELIDES, ALESSANDRA - University Of Vermont; CHAKRABORTY, PURNA - Montclair State University; HARPER, KELCEY - Vermont Department Of Health; DEVLIN, VALERIE - Vermont Department Of Health; MARTIN, LAURIE - Vermont Department Of Health; LUNNA, ALIA - University Of Vermont; BLACKWELL, HANNAH - University Of Vermont; NGUYEN, SARAH - Former ARS Employee; PENNY, ANNA - University Of Vermont; ETTER, ANDREA - University Of Vermont

Submitted to: Zoonoses and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2025
Publication Date: 7/29/2025
Citation: Patch, C., Larsen, K., Armstrong, C.M., Kanrar, S., Michaelides, A., Chakraborty, P., Harper, K., Devlin, V., Martin, L., Lunna, A., Blackwell, H., Nguyen, S.C., Penny, A., Etter, A. 2025. Prevalence, risk factors, and human health implications of Salmonella enterica and Campylobacter spp. in Vermont backyard poultry. Zoonoses and Public Health. http://doi.org/10.1111/zph.70004.
DOI: https://doi.org/10.1111/zph.70004

Interpretive Summary: There has been increased interest in raising backyard poultry since the pandemic and, with that, a concurrent spike in backyard poultry associated illnesses. Considering that backyard poultry flocks are not subjected to antibiotic feeding and typically have less cross contamination than flocks in commercial production, backyard poultry offers a unique perspective into the presence of foodborne pathogens and the spread of antimicrobial resistance in poultry. To investigate these important aspects of food safety, 54 isolates of Salmonella were obtained from soiled bedding of backyard poultry on 12 farms in Vermont. Using both genotypic and phenotypic data, the antibiotic resistance profile of each isolate was assessed and the serotypes defined. Here, Salmonella Schwarzengrund was the most common serovar isolated, followed by Kentucky, Hadar, and Enteritidis. All isolates of Salmonella Hadar obtained showed resistance to multiple antibiotics, while the Newport and Infantis isolates did not show any resistance. Importantly, four Salmonella isolates had intermediate resistance to ciprofloxacin and one was resistant to ampicillin. The backyard poultry farms were also tested for the presence of Campylobacter, with 19% of farms testing positive for its presence. Taken together, the presence of foodborne pathogens is not uncommon in Vermont backyard poultry, indicating the possible risk to public health associated with backyard poultry farms.

Technical Abstract: Introduction: Backyard poultry (BYP) are increasingly linked to cases of campylobacteriosis and salmonellosis. Methods: Between 2022 and 2024, soiled bedding samples from 70 BYP farms were tested for Campylobacter spp. and/or Salmonella enterica. Results: Nine farms (12.86%) had at least one sample positive for S. enterica, while 19.05% (12/63) tested positive for Campylobacter spp. We sequenced 54 S. enterica isolates from eight farms in this sample and four farms from previous sampling in 2021 (n = 12total farms) to determine the genetic characteristics of S. enterica from backyard poultry. Salmonella Schwarzengrund was the most common serovar (33%; 18/54) found, followed by Kentucky (16.7%; 9/54) and serovars Hadar (14.8%; 8/54) and Enteritidis(14.8%; 8/54). Though over half of isolates (51.9%; 28/54) exhibited no predicted genotypic or phenotypic resistance to antimicrobials, some serovars such as Salmonella Hadar were resistant to multiple antimicrobials. Four isolates had intermediate phenotypic resistance to ciprofloxacin and two were resistant to ampicillin. Conclusions: In summary, the frequency of Campylobacter and Salmonella in BYP populations of Vermont may pose a significant public health risk. Although the rate of antimicrobial resistance was low among S. enterica isolates, resistance to medically important antibiotics was observed, and isolate serovars aligned with serovars implicated in human illness in Vermont.