Simulated flock-level shedding characteristics of Turkeys in ten thousand bird houses infected with H7 low pathogenicity avian influenza virus strains

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Understanding the amount of virus shed at the flock level by birds infected with low pathogenicity avian influenza virus (LPAIV) over time can help inform the type and timing of activities performed in response to a confirmed LPAIV-positive premises. To this end, we developed a mathematical model which allows us to estimate viral shedding by 10,000 turkey toms raised in commercial turkey production in the United States, and infected by H7 LPAIV strains. We simulated the amount of virus shed orally and from the cloaca over time, as well as the amount of virus in manure. In addition, we simulated the threshold cycle value (Ct) of pooled oropharyngeal swabs from birds in the infected flock tested by real-time reverse transcription polymerase chain reaction. The simulation model predicted that little to no shedding would occur once the highest threshold of seroconversion was reached. Substantial amounts of virus in manure (median 1.5 × 108 and 5.8 × 109; 50% egg infectious dose) were predicted at the peak. Lastly, the model results suggested that higher Ct values, indicating less viral shedding, are more likely to be observed later in the infection process as the flock approaches recovery.

Original languageEnglish (US)
Article number2509
Issue number12
StatePublished - Dec 2021

Bibliographical note

Funding Information:
The authors were funded by a United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) grant 2020-67015-31394 (Evaluating how immunosuppression influences influenza A virus transmission and evolution in wild and domestic birds), and from a cooperative agreement between the Center for Epidemiology and Animal Health (CEAH) of the USDA, Animal and Plant Health Inspection Service (APHIS) Veterinary Services (VS), and the University of Minnesota (UMN) as USDA Award #AP20VSCEAH00C054 (Quantitative Analyses to Manage Transboundary/Emerging Diseases and Support Risk-based Decision-making). C.C. is also funded by the B.S. Pomeroy Chair in Avian Health at the University of Minnesota, College of Veterinary Medicine. The authors thank Erica Spackman of the Southeast Poultry Research Laboratory for providing raw data from her 2010 turkey inoculation study.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.


  • Avian influenza
  • Epidemiology
  • Mathematical modeling
  • Outbreak management
  • Poultry


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