An official website of the United States government.

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Consequences of Stress and Diet on the Immune and Endocrine Systems of Cattle and Their Effects on the Seasonal Shedding of Escherichia coli O157-H7

Loneragan, Guy; Karunasena, Enusha; Brashears, Mindy
Texas Tech University
Start date
End date
The purpose of this study is identifying the mechanism responsible for increased shedding of E. coli O157:H7, growth, and virulence factor expression. The hypothesis for this study, is that changes in diet do influence the expression of NE levels by the endocrine system, and the activation of the immune system in cattle during stressful versus non-stressful conditions, during various seasons, which does lead to increased expression of virulence factors and shedding of E. coli during the peaks seasons.

The stated objectives for this work were to evaluate the influence of diet and stress conditions on the homeostasis of the immune and endocrine system of cattle. Second, to determine the influence of these factors on the shedding of E. coli O157:H7, over the course of four seasons (winter, spring, summer, and fall).

More information
Findings: Pathogenic E.coli 0157:H7 shedding is a major source of concern in the food and cattle industry. Eliminating contamination sources and preventing the transmission of these organisms, is a goal for researchers and cattle and beef producers. This research sheds insight, into why increased shedding may occur during certain times. We demonstrate experimental evidence which suggests that bacterial organisms like pathogenic E. coli O157:H7 can use cattle stress hormones and other cattle-related conditions as a signal to grow more and to become more potent.

This study also tells us that, when cattle are stressed, their health, diet, and body-signals (stress hormones) are communication sources for bacteria. Bacteria use these cattle-related signals as a message, which causes them to grow rapidly and become more powerful, because they find their environment to be more stressful. All of these conditions in the cattle are likely events that can lead pathogenic bacteria, like E. coli O157:H7, to be shed more in greater cattle- stress conditions.

Funding Source
Nat'l. Cattlemen's Beef Assoc.
Project number
Escherichia coli
Bacterial Pathogens