The Effect of Herd Health on Microbial Contamination of Swine Carcasses at Processing and Potential

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The Effect of Herd Health on Microbial
Contamination of Swine Carcasses at Processing
and Potential Implications to Human Health

• Jean Brudvig, DVM, MPH
• Iowa State University
• Food Risk Modeling and Policy Lab

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Co-Authors

• Drs. H. Scott Hurd, Jim Dickson, Ron Griffith,
  Iowa State University
• Dr. Jovan Mirceta and Miroslava Polovinski,
  University of Novi Sad, Serbia Montenegro
• Dr. Neal Matthews, Premium Standard Farms, MO

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Background

• Controversy antibiotics in food animals
• Antibiotic-resistant human pathogens
• Risk-risk approach
• How does pig health affect human health?
• Antibiotics have been shown to increase animal
  health
• A healthier animal may mean healthier food
• Carcass contamination proxy for
• human risk

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Research Questions

• Is there a link between animal health and human
  risk?
• How well do physical indicators of infectious
  disease on the carcass relate to the level of
  fecal bacterial carcass contamination?

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Physical indicators
Fecal/foodborne contamination
Subclinical pig illness
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Materials and Methods Contamination

• Large, integrated pork processor
• 8 runs, each representing 330 pigs
• Systematic random sampling
• Skin pre-scald (SC)
• Bung (pelvic) cavity (B)
• Pleural cavity (PL)
• Following evisceration, before blast chiller
• Close to final product entering food supply

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Collection, SC
Collection, B
Collection, PL
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Materials and Methods Contamination

• 5 carcasses/sponge, 7 sponges/group, 8 groups
  280 total carcasses represented
• Cultured and quantified Campylobacter,
  Enterococcus, Enterobacteriaceae spp.
• Cultured Salmonella spp.

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Methods Pooling
Replicate or run
8 replicates
7 sponges/ replicate
5 carcasses/ sponge
5 5 5 5 5 5 5
56 total pools (sponges) 280 total head
represented
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Methods Antibiotic Use Group

• Antibiotic-free (ABF)
• Never received antibiotics
• Sick pigs in this group treated, removed
• Best of the best
• Conventional (CON)
• Received antibiotics throughout life
• Growth promotion, disease prevention/treatment
• Sick, treated pigs remained in group
• Cannot compare health of populations

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Methods Health Indicators

• Representative health indicators were analyzed to
  assess overall herd health (2,625 total head)
• Peel-out/pleuritis pleural lining must be
  forcibly pulled from ribcage during evisceration
• Fatigue animal exhibits respiratory distress,
  reluctance to keep up, recumbency
• Abscessed heads head condemned

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Methods Health and Contamination

• Group prevalence
• Health of carcasses with lesions
• Contamination of carcasses with bacterial
  pathogens
• Not matched
• Preliminary study
• Place to start
• Crude measures

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Pleuritis with lung adhesions
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Statistical Methods

• Association/relationship between
• Health carcasses with lesions
• Contamination carcasses
• Identify correlations between health of group,
  bacterial contamination
• Multivariate linear regression
• Antibiotic use group as covariate

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Results Descriptive

• Bacterial contamination (avg. group prevalence)

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Results Descriptive

• Health indicators (total head2,625)
• Peel-outs 186 (7.1)
• Fatigue 13 (0.5)
• Abscessed Heads 44 (1.7)
• Few health problems overall

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Regression CoefficientsHealth and Contamination
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Multivariate Linear Regression (Antibiotic Use
Covariate)
ß4.4 (pts) ß5.1 (pts)
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Discussion

• Quantifiable () correlation between subclinical
  (peel-outs, fatigue) animal illness and human
  health risk
• If chronic illness is not detected antemortem,
  the lesions could
• Impede proper evisceration
• Increase carcass contamination
• Ultimately increase human foodborne risk

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Discussion Risk-risk of Antibiotic Use

• Healthy pigs may decrease human risk
• Healthier pigs may have less carcass
  contamination with foodborne pathogens
• Less risk to human health
• Relatively low correlations can matter!
• Small changes in animal health may have a
  disproportionately large impact on human health

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Swine Health Effects Carcass Quality and
Ultimately Human Health
Antibiotic Use
Discard
Herd Management
Sick Animals
Animal Health
Healthy Animals
Disease
Processing
Other Factors
Inspection
Trim
Susceptible Humans
Uncontaminated Product
Sick Humans
Contaminated Product
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Implications to Public Health

• Demonstration of positive relationship
• Subclinical pig health
• Fecal Campylobacter contamination
• A healthier animal
• May have less carcass contamination
• Could help reduce human disease

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Future work needed

• Data show enough support for our hypotheses to
  warrant further study
• Greater number of pigs
• Higher level of matching
• Individual pig tracking
• Less group level analysis
• Organoleptic method
• veterinary pathology

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Acknowledgements

• Sasi Malladi data analysis
• Brenda Sue Patton laboratory work
• Annette OConnor internal review

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Questions?