Summary In April and November of 2018, multiple commercial laying hen flocks within the same company presented with a sharp increase in mortality and drop in egg production that persisted for several days. These flocks showed striking necropsy lesions consistent with systemic infection and responded to antimicrobial treatment in the feed. Staphylococcus aureus (SA) was the most frequently isolated organism from multiple tissues including comb and wattle lesions, lungs, liver, ovary, spleen, and bone marrow. Given such an uncommon presentation of SA, which is known as a secondary opportunistic pathogen, a challenge study was conducted to evaluate its role is these disease outbreaks. In the present study, laying hens of 2 ages (22 and 96 weeks) were inoculated with SA via 3 routes: oral gavage (OG), subcutaneous injection (SC), and intravenous injection (IV). Both young and old hens in the IV group showed a significant increase in body temperature and drop in body weight; however, the clinical signs observed in the naturally-occurring outbreaks were not present. SA was re-isolated at multiple time points post-challenge from all challenge groups except the negative control group. While the SC group showed localized necrosis at the injection site, microscopic changes were different from changes observed in birds from the natural outbreaks. Despite observed initial differences in route and age, the SA challenge strain was not capable of reproducing the disease on its own. The results of this study indicate that SA may have played a role in the increased mortality, clinical signs, and necropsy lesions reported with the naturally-occurring outbreaks. However, SA should still be considered as a secondary opportunistic pathogen. Other factors that could have caused the initial insult are stress, immunosuppression, or other primary infectious agents. The results of this study may aid veterinary diagnosticians, clinicians, and all poultry professionals to include SA in their differentials list as a secondary opportunistic pathogen in similar cases. This is an uncommon presentation and further field observations and clinical studies are needed to better elucidate the pathogenesis of this disease, which will in turn help to prevent future outbreaks.
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Research Article|
January 19 2021
Comparison of naturally-occurring versus experimental infection of Staphylococcus aureus septicemia in Laying Hens in two different age groups
Yuko Sato
;
Yuko Sato
Iowa State University
Reviewer
VDPAM
1809 S Riverside Dr
2430 Lloyd Vet Med Center
UNITED STATES
Ames
Iowa
50011-3619
Iowa State University
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Mohamed El-Gazzar
Mohamed El-Gazzar
Iowa State University
Assistant Professor
Veterinary Preventive Medicine
1809 South River Drive
UNITED STATES
Ames
IA
50011
17065403037
Search for other works by this author on:
Avian Dis (2021)
Article history
Received:
October 21 2020
Revision Received:
January 11 2021
Accepted:
January 18 2021
Citation
Meaghan Meyer, Elizabeth Bobeck, Yuko Sato, Mohamed El-Gazzar; Comparison of naturally-occurring versus experimental infection of Staphylococcus aureus septicemia in Laying Hens in two different age groups. Avian Dis 2021; doi: https://doi.org/10.1637/aviandiseases-D-20-00118
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