Author
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Keen, James |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 3/20/2003 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Over the past decade, a steady stream of sporadic human illness punctuated by occasional large food- or water-borne outbreaks and massive food recalls have driven a sustained and intense public and private research effort on the nature of STEC O157 in humans, food, the environment, and livestock. While the human epidemiological picture has remained relatively stable, our view of the on-farm epidemiology in livestock has changed drastically in recent years. Originally believed to be a rare inhabitant of the distal gastrointestinal (GI) tract of cattle and an infrequent fecal contaminant, STEC O157 is now known to occupy a broad, if transient, comfort zone on the farm environment. While STEC O157 appears to be especially comfortable in the distal bovine GI tract, it also finds frequent refuge in many non-bovine and/or non-fecal locations, including hide surfaces, the anterior ruminant GI tract, non-ruminant livestock (such as swine), feed, water, soil, and insects. Three common on-farm epidemiologic themes have emerged: (1) short-term local endemic instability of livestock infection and farm environmental contamination, (2) extreme long-term regional seasonality in prevalence (summer peaks and winter nadirs), and (3) frequent and sometimes high bovine, non-bovine, and non-fecal pathogen isolation on farms. Recent reports strongly suggest that STEC O157 is endemic on virtually all U.S. livestock operations, with individual animal prevalence sometimes approaching 100%. This revised view of STEC O157 on farms was technology driven via improved diagnostic reagents, better sampling protocols, and more efficient culture and isolation techniques. In particular, the development and widespread adoption of immunomagnetic separation (IMS) was critical, allowing more efficient concentration and detection of STEC O157 from compositionally- and microbiologically-complex farm sample matrices. New molecular techniques have also improved our ability to characterize and compare farm isolates, to define clonality and to estimate ecological or epidemiologic inter-relationships. Unfortunately, epidemiologic insights to date have not identified any effective or practical risk reduction practices that can be implemented on farms. Thus, while we can better describe STEC O157 on farm epidemiology, we can as yet only observe and not modify it. Pre-harvest (live animal) food safety remains an elusive if desirable goal for STEC O157. |
