|Schroeder, Sasha - TX A&M UNIVERSITY|
Submitted to: Society for General Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 2005
Publication Date: April 4, 2005
Citation: Edrington, T.S., Schultz, C.L., Schroeder, S.B., Callaway, T.R., Genovese, K.J., Anderson, R.C., Nisbet, D.J. 2005. Do hormones play a role in the seasonal shedding of Escherichia coli O157:H7 in ruminants [abstract]? Society for General Microbiology. p. 61. Technical Abstract: Seasonal shedding of E. coli O157:H7 (EC) in ruminants is well documented; however, reasons for this phenomenon are unknown. We hypothesize that seasonal shedding of EC is a result of physiological responses by the animal to changing daylength. In a series of experiments utilizing naturally-infected beef cattle and experimentally-infected sheep, we examined the effect of exogenous melatonin administration, and chemical inhibition of the thyroid, on fecal shedding and gastro-intestinal (GIT) populations of EC. Animals treated daily with a low oral dose of melatonin (mg) had shedding patterns and GIT populations of EC similar to controls. However, when a high dose of melatonin (g) was orally administered to naturally-infected cattle, the number of cattle shedding EC was lower (P = 0.05) compared to control steers. Chemical inhibition of the thyroid, via administration of propyl-thiouraracil (PTU), had no effect on fecal shedding or GIT populations in naturally- or experimentally-infected cattle and sheep. However, following termination of the PTU treatment in the naturally-infected cattle, a greater percentage of PTU treated animals shed EC compared to control steers. Early results indicate that hormones known to respond to changing daylength may play a role in the seasonal shedding of EC in ruminants.