The objective of this study was to determine the effects of farm management and environmental factors on preharvest spinach contamination with generic Escherichia coli as an indicator of fecal contamination. A repeated cross-sectional study was conducted by visiting spinach farms up to four times per growing season over a period of 2 years (2010 to 2011). Spinach samples (n ‫؍‬ 955) were collected from 12 spinach farms in Colorado and Texas as representative states of the Western and Southwestern United States, respectively. During each farm visit, farmers were surveyed about farm-related management and environmental factors using a questionnaire. Associations between the prevalence of generic E. coli in spinach and farm-related factors were assessed by using a multivariable logistic regression model including random effects for farm and farm visit. Overall, 6.6% of spinach samples were positive for generic E. coli. Significant risk factors for spinach contamination with generic E. coli were the proximity (within 10 miles) of a poultry farm, the use of pond water for irrigation, a >66-day period since the planting of spinach, farming on fields previously used for grazing, the production of hay before spinach planting, and the farm location in the Southwestern United States. Contamination with generic E. coli was significantly reduced with an irrigation lapse time of >5 days as well as by several factors related to field workers, including the use of portable toilets, training to use portable toilets, and the use of hand-washing stations. To our knowledge, this is the first report of an association between field workers' personal hygiene and produce contamination with generic E. coli at the preharvest level. Collectively, our findings support that practice of good personal hygiene and other good farm management practices may reduce produce contamination with generic E. coli at the preharvest level.

No abstract

Using serology and bacterial culture, we determined the prevalence of Brucella spp. and the antibody to Brucella spp. in a feral swine (Sus scrofa) population in proximity to a cattle herd that was culture positive for Brucella abortus and Brucella suis in north-central Texas, USA. During a prospective cross-sectional quantitative study in April 2005, we collected blood and tissue samples from 40 feral swine within a 30-km radius of the infected herd. Serum samples were tested by the Rose Bengal test, particle concentration fluorescence immunoassay, and fluorescence polarization assay. In addition, tissue samples were cultured, and the Brucella species and biovar determined. Four feral swine were Brucella positive by serology, and two were culture positive for B. suis biovar 1. Of the culture-positive swine, one was concurrently antibody and culture positive, and one was culture positive only. The presumptive source of the B. suis infection in the index cattle herd was likely the surrounding feral swine population. Because B. abortus was not cultured from the feral swine, it is unlikely that the source of the B. abortus infection in the index herd originated from the feral swine. Endemic diseases in feral swine populations can pose a disease threat to livestock and a zoonotic risk to humans.