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      Prevalence and risk factors associated with Campylobacter spp. and Salmonella enterica in livestock raised on diversified small-scale farms in California

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          Diversified farms are operations that raise a variety of crops and/or multiple species of livestock, with the goal of utilising the products of one for the growth of the other, thus fostering a sustainable cycle. This type of farming reflects consumers' increasing demand for sustainably produced, naturally raised or pasture-raised animal products that are commonly produced on diversified farms. The specific objectives of this study were to characterise diversified small-scale farms (DSSF) in California, estimate the prevalence of Salmonella enterica and Campylobacter spp. in livestock and poultry, and evaluate the association between farm- and sample-level risk factors and the prevalence of Campylobacter spp. on DSSF in California using a multilevel logistic model. Most participating farms were organic and raised more than one animal species. Overall Salmonella prevalence was 1.19% (95% confidence interval (CI 95) 0.6–2), and overall Campylobacter spp. prevalence was 10.8% (CI 95 = 9–12.9). Significant risk factors associated with Campylobacter spp. were farm size (odds ratio (OR) 10–50 acres: less than 10 acres = 6, CI 95 = 2.11–29.8), ownership of swine (OR = 9.3, CI 95 = 3.4–38.8) and season (OR Spring: Coastal summer = 3.5, CI 95 = 1.1–10.9; OR Winter: Coastal summer = 3.23, CI 95 = 1.4–7.4). As the number of DSSF continues to grow, evaluating risk factors and management practices that are unique to these operations will help identify risk mitigation strategies and develop outreach materials to improve the food safety of animal and vegetable products produced on DSSF.

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          Prevalence, distribution, and diversity of Salmonella enterica in a major produce region of California.

          A survey was initiated to determine the prevalence of Salmonella enterica in the environment in and around Monterey County, CA, a major agriculture region of the United States. Trypticase soy broth enrichment cultures of samples of soil/sediment (n = 617), water (n = 252), wildlife (n = 476), cattle feces (n = 795), and preharvest lettuce and spinach (n = 261) tested originally for the presence of pathogenic Escherichia coli were kept in frozen storage and later used to test for the presence of S. enterica. A multipathogen oligonucleotide microarray was employed to identify a subset of samples that might contain Salmonella in order to test various culture methods to survey a larger number of samples. Fifty-five of 2,401 (2.3%) samples yielded Salmonella, representing samples obtained from 20 different locations in Monterey and San Benito Counties. Water had the highest percentage of positives (7.1%) among sample types. Wildlife yielded 20 positive samples, the highest number among sample types, with positive samples from birds (n = 105), coyotes (n = 40), deer (n = 104), elk (n = 39), wild pig (n = 41), and skunk (n = 13). Only 16 (2.6%) of the soil/sediment samples tested positive, and none of the produce samples had detectable Salmonella. Sixteen different serotypes were identified among the isolates, including S. enterica serotypes Give, Typhimurium, Montevideo, and Infantis. Fifty-four strains were sensitive to 12 tested antibiotics; one S. Montevideo strain was resistant to streptomycin and gentamicin. Pulsed-field gel electrophoresis (PFGE) analysis of the isolates revealed over 40 different pulsotypes. Several strains were isolated from water, wildlife, or soil over a period of several months, suggesting that they were persistent in this environment.
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            Comparison of methods for estimating the intraclass correlation coefficient for binary responses in cancer prevention cluster randomized trials.

            The intraclass correlation coefficient (ICC) is a fundamental parameter of interest in cluster randomized trials as it can greatly affect statistical power. We compare common methods of estimating the ICC in cluster randomized trials with binary outcomes, with a specific focus on their application to community-based cancer prevention trials with primary outcome of self-reported cancer screening. Using three real data sets from cancer screening intervention trials with different numbers and types of clusters and cluster sizes, we obtained point estimates and 95% confidence intervals for the ICC using five methods: the analysis of variance estimator, the Fleiss-Cuzick estimator, the Pearson estimator, an estimator based on generalized estimating equations and an estimator from a random intercept logistic regression model. We compared estimates of the ICC for the overall sample and by study condition. Our results show that ICC estimates from different methods can be quite different, although confidence intervals generally overlap. The ICC varied substantially by study condition in two studies, suggesting that the common practice of assuming a common ICC across all clusters in the trial is questionable. A simulation study confirmed pitfalls of erroneously assuming a common ICC. Investigators should consider using sample size and analysis methods that allow the ICC to vary by study condition.
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              Cattle and sheep farms as reservoirs of Campylobacter


                Author and article information

                Epidemiol Infect
                Epidemiol. Infect
                Epidemiology and Infection
                Cambridge University Press (Cambridge, UK )
                12 December 2019
                : 147
                [1 ]Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis , Davis, CA 95616, USA
                [2 ]Western Center for Food Safety, University of California-Davis , Davis, CA 95616, USA
                Author notes
                Author for correspondence: A. F. A. Pires, E-mail: apires@

                Present address: BIOEPAR, INRAE, Oniris, 44307, Nantes, France.

                © The Author(s) 2019

                This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Tables: 2, References: 61, Pages: 9
                Original Paper


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