Searching for Suitable Indicator Viruses of Fecal Contamination for Pork Carcass Processing

Introduction: There are concerns about the zoonotic transmission of viruses through undercooked pork products. Enteric viruses are shed in fecal material and can potentially contaminate carcasses during meat processing operations. There is a lack of information on suitable indicator viruses for pathogenic enteric viruses in the meat processing chain.

Purpose: The study compared the incidence and levels of contamination of hog carcasses with F- coliphages (FC), porcine teschovirus (PTV), and porcine adenovirus (PAdV) at different stages of the dressing process to assess their potential as indicator viruses of fecal contamination.

Methods: One hundred swab samples (100 cm²) were collected from random sites on hog carcasses at 4 different stages of the dressing process and from meat cuts on 10 separate occasions over the span of a year from 2 pork processing plants (1000 samples in total, 500/plant). Numbers of viable FC were determined by plaque assay and the numbers of genome copies (GC) of PTV and PAdV were determined by q(RT)-PCR.

Results: For both processing plants, FC and PAdV were detected in 100% of samples and PTV was detected in 97% of samples after bleeding with a mean of 3.1 log plaque forming units  (PFU)/100 cm²  for FC and mean GC ranging between log 5.0 - 5.4 for PAdV and PTV. FC, PAdV and PTV were detected in 32%, 0%, and 3% of pork cuts, respectively, for plant 1 and detected in 20%, 3%, and 22% of pork cuts, respectively, for plant 2. Maximum numbers of FC, PAdV, and PTV were 2.2 - 4.0 log units lower on pork cuts than on eviscerated carcasses for plant 1 and 0.1 - 0.7 log units lower for plant 2.

Significance: Numbers of viable F-coliphages are high enough to trace through the carcass dressing process. Consumers are at risk when consuming undercooked meat contaminated with pathogenic enteric viruses.