A conceptual framework for developing recommendations for no-harvest buffers around in-field feces

Daniel L. Weller, Jasna Kovac, David J. Kent, Sherry Roof, Jeffrey I. Tokman, Erika Mudrak, Martin Wiedmann

Research output: Contribution to journalArticle

Abstract

Results of previous studies revealed that (i) splash can transfer microbes from in-field feces to preharvest produce and (ii) wildlife can be vectors for the introduction of foodborne pathogens into produce fields. However, few peer-reviewed studies have been conducted to examine pathogen transfer from wildlife feces to in-field produce via splash during irrigation. Although two previous studies found a significant relationship between distance and Escherichia coli transfer via splash, the studies sampled produce < m from the feces. The present study was conducted to refine our understanding of the impact of distance on E. coli splash. Two trials were conducted 1 month apart. For each trial, fecal pellets inoculated with a three-strain E. coli cocktail were placed in a lettuce field 2.5 h before irrigation. After irrigation, E. coli levels on lettuce heads 0 to 6 m from the pellets were determined. Although E. coli was not detected in any of the heads ≥2 m from the fecal pellets (n=39), 39% of heads (13 of 33) < m from the pellets tested positive for E. coli. According to logistic regression, the odds of harvesting a head that tested positive for E. coli decreased by a factor of 50 (odds ratio, 0.02; 95% confidence interval, <,0.01, 0.28; P=0.004) for each meter increase in the distance between the lettuce and the feces. Thus, the likelihood of E. coli transfer from feces to produce should be minimal at a given distance from the feces. Our model can be used to predict the probability of harvesting a microbially contaminated lettuce head following implementation of a no-harvest buffer around in-field feces. For example, our model suggests that the probability of harvesting a contaminated head was 0.1% at 3 m from the feces. Although the approaches utilized in this study provide a conceptual framework that can be used to help define appropriate no-harvest buffers, delineation of appropriate buffer zones requires additional information (e.g., acceptable risk and regional data). HIGHLIGHTS • None of the 39 lettuce heads > 2 m from the feces had detectable levels of E. coli. • Thirteen (39%) of the 33 heads > 2 m from the feces had detectable levels of E. coli. • Odds of harvesting E. coli-contaminated lettuce decrease with distance from feces. • Analyses provide a framework for estimating no-harvest buffers around in-field feces. • Risk assessments are needed to set appropriate buffer zones for different regions.

Original languageEnglish (US)
Pages (from-to)1052-1060
Number of pages9
JournalJournal of Food Protection
Volume82
Issue number6
DOIs
StatePublished - Jun 1 2019

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Feces
Buffers
buffers
feces
Escherichia coli
wildlife
Lettuce
peers
food pathogens
lettuce
risk assessment
Head
irrigation
microorganisms
pathogens

All Science Journal Classification (ASJC) codes

  • Food Science
  • Microbiology

Cite this

Weller, Daniel L. ; Kovac, Jasna ; Kent, David J. ; Roof, Sherry ; Tokman, Jeffrey I. ; Mudrak, Erika ; Wiedmann, Martin. / A conceptual framework for developing recommendations for no-harvest buffers around in-field feces. In: Journal of Food Protection. 2019 ; Vol. 82, No. 6. pp. 1052-1060.
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title = "A conceptual framework for developing recommendations for no-harvest buffers around in-field feces",
abstract = "Results of previous studies revealed that (i) splash can transfer microbes from in-field feces to preharvest produce and (ii) wildlife can be vectors for the introduction of foodborne pathogens into produce fields. However, few peer-reviewed studies have been conducted to examine pathogen transfer from wildlife feces to in-field produce via splash during irrigation. Although two previous studies found a significant relationship between distance and Escherichia coli transfer via splash, the studies sampled produce < m from the feces. The present study was conducted to refine our understanding of the impact of distance on E. coli splash. Two trials were conducted 1 month apart. For each trial, fecal pellets inoculated with a three-strain E. coli cocktail were placed in a lettuce field 2.5 h before irrigation. After irrigation, E. coli levels on lettuce heads 0 to 6 m from the pellets were determined. Although E. coli was not detected in any of the heads ≥2 m from the fecal pellets (n=39), 39{\%} of heads (13 of 33) < m from the pellets tested positive for E. coli. According to logistic regression, the odds of harvesting a head that tested positive for E. coli decreased by a factor of 50 (odds ratio, 0.02; 95{\%} confidence interval, <,0.01, 0.28; P=0.004) for each meter increase in the distance between the lettuce and the feces. Thus, the likelihood of E. coli transfer from feces to produce should be minimal at a given distance from the feces. Our model can be used to predict the probability of harvesting a microbially contaminated lettuce head following implementation of a no-harvest buffer around in-field feces. For example, our model suggests that the probability of harvesting a contaminated head was 0.1{\%} at 3 m from the feces. Although the approaches utilized in this study provide a conceptual framework that can be used to help define appropriate no-harvest buffers, delineation of appropriate buffer zones requires additional information (e.g., acceptable risk and regional data). HIGHLIGHTS • None of the 39 lettuce heads > 2 m from the feces had detectable levels of E. coli. • Thirteen (39{\%}) of the 33 heads > 2 m from the feces had detectable levels of E. coli. • Odds of harvesting E. coli-contaminated lettuce decrease with distance from feces. • Analyses provide a framework for estimating no-harvest buffers around in-field feces. • Risk assessments are needed to set appropriate buffer zones for different regions.",
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A conceptual framework for developing recommendations for no-harvest buffers around in-field feces. / Weller, Daniel L.; Kovac, Jasna; Kent, David J.; Roof, Sherry; Tokman, Jeffrey I.; Mudrak, Erika; Wiedmann, Martin.

In: Journal of Food Protection, Vol. 82, No. 6, 01.06.2019, p. 1052-1060.

Research output: Contribution to journalArticle

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T1 - A conceptual framework for developing recommendations for no-harvest buffers around in-field feces

AU - Weller, Daniel L.

AU - Kovac, Jasna

AU - Kent, David J.

AU - Roof, Sherry

AU - Tokman, Jeffrey I.

AU - Mudrak, Erika

AU - Wiedmann, Martin

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N2 - Results of previous studies revealed that (i) splash can transfer microbes from in-field feces to preharvest produce and (ii) wildlife can be vectors for the introduction of foodborne pathogens into produce fields. However, few peer-reviewed studies have been conducted to examine pathogen transfer from wildlife feces to in-field produce via splash during irrigation. Although two previous studies found a significant relationship between distance and Escherichia coli transfer via splash, the studies sampled produce < m from the feces. The present study was conducted to refine our understanding of the impact of distance on E. coli splash. Two trials were conducted 1 month apart. For each trial, fecal pellets inoculated with a three-strain E. coli cocktail were placed in a lettuce field 2.5 h before irrigation. After irrigation, E. coli levels on lettuce heads 0 to 6 m from the pellets were determined. Although E. coli was not detected in any of the heads ≥2 m from the fecal pellets (n=39), 39% of heads (13 of 33) < m from the pellets tested positive for E. coli. According to logistic regression, the odds of harvesting a head that tested positive for E. coli decreased by a factor of 50 (odds ratio, 0.02; 95% confidence interval, <,0.01, 0.28; P=0.004) for each meter increase in the distance between the lettuce and the feces. Thus, the likelihood of E. coli transfer from feces to produce should be minimal at a given distance from the feces. Our model can be used to predict the probability of harvesting a microbially contaminated lettuce head following implementation of a no-harvest buffer around in-field feces. For example, our model suggests that the probability of harvesting a contaminated head was 0.1% at 3 m from the feces. Although the approaches utilized in this study provide a conceptual framework that can be used to help define appropriate no-harvest buffers, delineation of appropriate buffer zones requires additional information (e.g., acceptable risk and regional data). HIGHLIGHTS • None of the 39 lettuce heads > 2 m from the feces had detectable levels of E. coli. • Thirteen (39%) of the 33 heads > 2 m from the feces had detectable levels of E. coli. • Odds of harvesting E. coli-contaminated lettuce decrease with distance from feces. • Analyses provide a framework for estimating no-harvest buffers around in-field feces. • Risk assessments are needed to set appropriate buffer zones for different regions.

AB - Results of previous studies revealed that (i) splash can transfer microbes from in-field feces to preharvest produce and (ii) wildlife can be vectors for the introduction of foodborne pathogens into produce fields. However, few peer-reviewed studies have been conducted to examine pathogen transfer from wildlife feces to in-field produce via splash during irrigation. Although two previous studies found a significant relationship between distance and Escherichia coli transfer via splash, the studies sampled produce < m from the feces. The present study was conducted to refine our understanding of the impact of distance on E. coli splash. Two trials were conducted 1 month apart. For each trial, fecal pellets inoculated with a three-strain E. coli cocktail were placed in a lettuce field 2.5 h before irrigation. After irrigation, E. coli levels on lettuce heads 0 to 6 m from the pellets were determined. Although E. coli was not detected in any of the heads ≥2 m from the fecal pellets (n=39), 39% of heads (13 of 33) < m from the pellets tested positive for E. coli. According to logistic regression, the odds of harvesting a head that tested positive for E. coli decreased by a factor of 50 (odds ratio, 0.02; 95% confidence interval, <,0.01, 0.28; P=0.004) for each meter increase in the distance between the lettuce and the feces. Thus, the likelihood of E. coli transfer from feces to produce should be minimal at a given distance from the feces. Our model can be used to predict the probability of harvesting a microbially contaminated lettuce head following implementation of a no-harvest buffer around in-field feces. For example, our model suggests that the probability of harvesting a contaminated head was 0.1% at 3 m from the feces. Although the approaches utilized in this study provide a conceptual framework that can be used to help define appropriate no-harvest buffers, delineation of appropriate buffer zones requires additional information (e.g., acceptable risk and regional data). HIGHLIGHTS • None of the 39 lettuce heads > 2 m from the feces had detectable levels of E. coli. • Thirteen (39%) of the 33 heads > 2 m from the feces had detectable levels of E. coli. • Odds of harvesting E. coli-contaminated lettuce decrease with distance from feces. • Analyses provide a framework for estimating no-harvest buffers around in-field feces. • Risk assessments are needed to set appropriate buffer zones for different regions.

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