Nancy Cornick, an ISU associate professor of veterinary microbiology who previously researched the issue for the Food Safety Consortium, showed that uninfected pigs sharing pens with infected pigs could also become infected. In more recent research, it appeared that transmission of the organism could be accomplished through the air even when infected pigs were separated from uninfected pigs. Air samples
“In this study, some of the aerosols could be from hosing the pen, although we scrape the pens first before we hose them,” Cornick explained. “One of the air samples was taken 24 hours after the pens had been cleaned.” That suggests infectious aerosols may remain suspended for at least that long or that the pigs themselves may be creating aerosolised E. coli
. Easily transmitted
“What it says to me is that if the organism is in the environment with the pig, it’s very easily transmitted and the infectious dose is very low,” Cornick said. Cornick had also performed a similar experiment with sheep and found that E. coli
wasn’t transmitted as easily as in pigs. Other experiments have also shown that E. coli
O157:H7 can establish and maintain a population in some pigs’ intestinal tracts for at least two months, indicating that the bacterium can colonize swine. The incidence of the pathogen in swine remains small but worthy of notice.
Cornick noted that one U.S. slaughter facility recovered E. coli
O157:H7 in 2% of its pigs, and the bacterium has also been recovered from healthy swine in Japan, Chile, the Netherlands, Norway and Sweden.
Cornick seeks to follow up the swine research by performing the same experiments with cattle, which are considered the major reservoir of E. coli
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