Abstract
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 and ; 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.
Highlights
H5 and H7 Low pathogenicity avian influenza (LPAI) virus (LPAIV) strains are of special concern, as they have been known to mutate into highly pathogenic avian influenza (HPAI), a devastating virus that can cause close to 100% mortality in an infected flock
The amount of virus shed by infectious birds subsequent to this time accounted for very little of the total: Approximately all shedding from oral and cloacal routes was predicted to have occurred by the time 98% seroconversion was observed for both datasets
Analysis,the theamount amountofofvirus virusshed shed from oral and cloacal routes over by thousand turkey toms in a house exposed to was simulated from a stochastic disease ten thousand turkey toms in a house exposed to low pathogenicity avian influenza virus (LPAIV) was simulated from a stochastic transmission model, parameterized based onbased largescale production in the U.S, to provide disease transmission model, parameterized on largescale production in the
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Low pathogenicity avian influenza (LPAI) can cause reduced egg production and weight gain in infected birds, cause increased flock mortality, and impact the trade of poultry and poultry products [1]. H5 and H7 LPAI virus (LPAIV) strains are of special concern, as they have been known to mutate into highly pathogenic avian influenza (HPAI), a devastating virus that can cause close to 100% mortality in an infected flock. LPAI outbreak responses in the United States (U.S.) have used one of three strategies: depopulation (on-site destruction of the birds on infected premises), controlled marketing (maintaining birds on premises with heightened biosecurity until birds recover and are sent to processing), and, though less common in the U.S, vaccination [1,2]
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