Factors that influence mechanical transmission of porcine reproductive and respiratory syndrome virus at the time of unloading animals into slaughter plant lairage
James Lowe, DVM, MS; Ryan McCann, DVM; Laura Greiner, PhD
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Objectives: To estimate the impact of environmental conditions and management practices on the likelihood of cross-contamination of a pig transport vehicle with porcine reproductive and respiratory syndrome virus (PRRSV) during market-animal unloading.
Materials and methods: An experimental model was developed to simulate indirect contact involving footwear between an unloading dock and a pig transport vehicle. Two experiments were conducted. Experiment 1 evaluated temperature on the model trailer (4°C, 15°C, or 28°C) for 60 minutes after contact with the contaminated dock (32 contact replicates per temperature). In Experiment 2, conditions on the model dock were evaluated in a 2 × 2 × 2 factorial arrangement with repeated measures. Main effects were temperature (4°C or 32°C), ultraviolet light (ambient or supplemental), and mechanical scraping (de-bulked or not) with four contact events per combination. Samples were collected using a “Swiffer” (Procter & Gamble, Cincinnati, Ohio). All samples were tested for PRRSV using reverse-transcription polymerase chain reaction.
Results: Experiment 1: Temperature did not affect the amount of PRRSV RNA recovered. If PRRSV RNA was detected on the model dock, it was transferred and detected on the model trailer 80% of the time (95% CI, 70.0%-90.0%). Experiment 2: De-bulking resulted in a significant reduction in the likelihood of transfer (odds ratio = 0.14; 95% CI, 0.06-0.32).
Implications: Contact at the harvest plant lairage unloading is a risk factor for PRRSV transmission with inadequate livestock trailer hygiene. This risk can be mitigated through mechanical removal of gross contamination of the dock.
Keywords: porcine reproductive and respiratory syndrome virus, transportation, biosecurity, PRRSV
Cite as: Lowe J, McCann R, Greiner L. Factors that influence mechanical transmission of porcine reproductive and respiratory syndrome virus at the time of unloading animals into slaughter plant lairage. J Swine Health Prod 2017;25(1):19-23.
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