Escherichia coli O157:H7 in Feral Swine near Spinach Fields and Cattle, Central California Coast1
Michele T. Jay* , Michael Cooley‡, Diana Carychao‡, Gerald W. Wiscomb§, Richard A. Sweitzer¶, Leta Crawford-Miksza*, Jeff A. Farrar#, David K. Lau**, Janice O’Connell*, Anne Millington#, Roderick V. Asmundson**, Edward R. Atwill, and Robert E. Mandrell‡
Author affiliations: *California Department of Public Health, Richmond, California, USA; †University of California, Davis, California, USA; ‡US Department of Agriculture, Albany, California, USA; §US Department of Agriculture, Sacramento, California, USA; ¶University of North Dakota, Grand Forks, North Dakota, USA; #California Department of Public Health, Sacramento, California, USA; **US Food and Drug Administration, Alameda, California, USA;
Figure 1. Left: aerial (2 m) photograph of ranch A showing overlapping circular buffer regions around feral swine trap 1 and trap 2 (San Benito Crop Year 2006; Image Trader, Flagstaff, AZ). The radius for the buffer (1.8 km) is the circumference of the mean home range for feral swine in mainland California (8). Estimated density = 4.6 swine/km2 and total area = (A + B + C) – D = 14.8 km2. Areas A, B, and C, combined with counts of individual feral swine from October through November 2006, were used to calculate the average population density. Bottom left: digital infrared photograph of feral swine at trap 1. Right: potential risk factors for Escherichia coli O157:H7 contamination of spinach at ranch A: 1) Feral sow and piglets sharing rangeland with cattle; 2) feral swine feces, tracks, and rooting in a neighboring spinach field; 3) cattle in surface water.
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