Applied and Environmental Microbiology
Experimental and field studies of Escherichia coli O157:H7 in white-tailed deer
As a result of recent outbreaks of Escherichia coli O157:H7, there has been a renewed interest in studying this bacterium. Much research has been focused on cattle, since beef is thought to be the primary source of E coli O157:H7, but there have been case reports implicating venison as a source for this disease as well. The authors of this study set out to evaluate the importance of white-tailed deer in the transmission of E coli O157:H7.
This study has 2 parts. A controlled laboratory experiment was performed to evaluate the clinical response, fecal shedding, sites of bacterial localization, and associated lesions in deer inoculated with E coli O157:H7. In the experiment, 6 deer were orally inoculated with E coli O157:H7, 2 deer were orally inoculated with nontoxigenic E coli, and 1 deer was not inoculated. The deer that was not inoculated was housed with 1 of the 6 deer that had been inoculated with E coli O157:H7. The other deer were also housed in pairs. The deer were then euthanatized and necropsied at various intervals. Serologic and histopathologic studies were performed subsequently. Meanwhile, field researchers collected multiple stool samples from wild deer and nearby cattle across the southeastern United States.
Other than 2 of the 9 experimental deer developing mild nonhemorrhagic diarrhea, there was no apparent clinical response after E coli inoculation. The 1 deer that was not inoculated did show fecal shedding of E coli O157:H7. It was also noted that fecal shedding decreased with time. Pathologic studies showed high levels of E coli in the gastrointestinal tract of all euthanatized deer, but not in the uncooked meat. Field studies found evidence of E coli O157:H7 in rectal swabs of 3 (0.5%) of 609 individually sampled deer, but there was no evidence of E coli O157:H7 in fecal samples collected from the ground. Evidence of E coli O157:H7 was also found in the stool of 13 (4.3%) of 305 nearby cattle. The specific serotypes are included in the results. Studies of fresh venison collected by hunters in the area failed to isolate any E coli.
This study provides valuable data concerning the role of wild deer in the epidemiology of E coli O157:H7. The experimental portion is small in size, but the results agree with results obtained in similar cattle studies. The field research, on the other hand, is extensive and large scale. Although no E coli O157:H7 was obtained from fresh venison meat, case reports of human infection after eating venison have been documented. Based on the results of this study, deer are not as large a reservoir for E coli O157:H7 as cattle, but they likely play an important role in its spread, especially where deer live near cattle.
(Appl Environ Microbiol. 2001;67:1218–1224) J. R. Fischer, T. Zhao, M. P. Doyle, et al.
Article info
Identification
DOI: https://doi.org/10.1580/1080-6032(2001)012[0214:AOCL]2.0.CO;2
Copyright
© 2001 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.
