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United States Department of Agriculture

Agricultural Research Service

Title: Seasonality and Transmission of Shiga-Toxigenic Escherichia Coli Infections in Cattle: Agro-Ecological and Molecular Epidemiologic Evidence of a Role for Pest Flies

Authors
item Keen, James
item Durso, Lisa
item Gerhardt, Reid - UNIVERSITY OF TENNESSEE
item Jones, Carl - UNIVERSITY OF TENNESSEE
item Watson, Wes - NORTH CAROLINA STATE UNIV
item Hogsette, Jerome
item Keen, Douglas - HARRIS ANIMAL HOSPITAL

Submitted to: International Symposium and Workshop on Shiga Toxin ... Escherichia coli
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 2006
Publication Date: October 29, 2006
Citation: Keen, J.E., Durso, L.M., Gerhardt, R.R., Jones, C., Watson, W., Hogsette Jr, J.A., Keen, D. 2006. Seasonality and transmission of shiga-toxigenic Escherichia coli infections in cattle: Agro-ecological and molecular epidemiologic evidence of a role for pest flies. [abstract]. Proccedings of the 6th International Symposium on Shiga Toxin (Verocytotoxin)--Producing Escherichia coli Infections, October 29 - November 1, 2006, Melbourne, Australia. Poster No. P04.1.02.

Technical Abstract: The ecological or other basis for the strong observed summer prevalence peaks in Shiga-toxigenic Escherichia coli (STEC) O157 human and livestock infections and in meat and produce contamination remains unexplained and enigmatic. Using an agro-ecological approach to investigate livestock STEC seasonality, we examined the co-occurrence of STEC O157, O26, and O111 in livestock feces and in synanthropic muscoid pest flies live-trapped on beef and dairy farms and ranches. We hypothesized that the filth- and manure-associated life cycles and rapid reproduction of agricultural pest flies may enable them to function as reservoirs, mechanical vectors, or diagnostic markers of bovine STEC infections. More than 2000 freshly-deposited cattle fecal specimens and several hundred species-specific fly pools (representing thousands of individual flies) were collected in summer and cultured separately for STEC O157, O111, and O26 on >50 beef and dairy cattle operations in multiple geographic regions. Fly species cultured included house flies (Musca domestica), stable flies (Stomoxys calcitrans), face flies (Musca autumnalis), horn flies (Haematobia irritans) and blow flies (Calliphoridae species). While STEC O157 was found in all fly species examined, only house fly prevalence correlated positively with, and occurred at levels similar to, bovine fecal prevalence on cattle farms. Pulsed-field gel electrophoresis (PFGE) demonstrated that house flies carried STEC O157 strains indistinguishable from those found in cattle. Non-house fly STEC O157 fly prevalence was usually much lower than that found in either house flies or cattle on farms. STEC O111 with identical PFGE profiles were also isolated from house flies and cattle on the same farms. The isolation of STEC with indistinguishable molecular fingerprints from cattle and flies on the same farms at the same times confirms cross-species contamination or common source exposures in livestock environments, and provides evidence supportive of a role for pest flies, especially house flies, in STEC livestock transmission.

Last Modified: 8/30/2014