title: Effect of the thyroid on faecal shedding of E. coli O157:H7 and Escherichia coli in naturally infected yearling beef cattle.
abstract: OBJECTIVE
  To determine if thyroid function affects faecal shedding of Escherichia coli O157:H7.
  
  
  RESULTS
  Eight yearling cattle (n = 4 per treatment group), previously identified as shedding E. coli O157:H7, received either 0 or 10 mg 6-N-propyl-2-thiouracil (PTU) kg(-1) BW day(-1) for 14 days to reduce serum concentrations of the thyroid hormones, T(3) and T(4). Animals were monitored daily for changes in faecal shedding of E. coli O157:H7 and E. coli (EC) for the 14-day treatment period and an additional 7 days post-treatment. Body weight was measured weekly and serum concentrations of T(3) and T(4) were determined every 3 days. No differences in faecal shedding of E. coli O157:H7 were observed during the 14-day treatment period. However, compared with control animals, a greater percentage of PTU-treated cattle ejected E. coli O157:H7 on day 16 (100 vs 25%) and 18 (75 vs 0%) of the post-treatment period. Serum T(3) was lower in PTU-treated cattle during the 14-day treatment period and greater on day 18 of the post-treatment period.
  
  
  CONCLUSIONS
  Cattle with chemically altered thyroid hormones had similar shedding patterns of faecal E. coli O157:H7 and EC during the 14-day treatment period. However, faecal shedding of E. coli O157:H7 tended to be greater, and serum concentrations of T(3), were greater for PTU-treated cattle immediately following the termination of PTU treatment.
  
  
  CONCLUSIONS
  Short-term chemical inhibition of thyroid hormones had minimal effects on faecal shedding of E. coli O157:H7 in naturally infected cattle. However, a hyperthyroid state as observed postdosing might play a role in the seasonal shedding of E. coli O157:H7 in cattle.
authors.affiliation: USDA/ARS-Southern Plains Agricultural Research Center, College Station, TX 77845, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Schultz
authors.forename: T S
authors.initials: TS
authors.lastname: Edrington
authors.forename: S B
authors.initials: SB
authors.lastname: Schroeder
authors.forename: D M
authors.initials: DM
authors.lastname: Hallford
authors.forename: K J
authors.initials: KJ
authors.lastname: Genovese
authors.forename: T R
authors.initials: TR
authors.lastname: Callaway
authors.forename: R C
authors.initials: RC
authors.lastname: Anderson
authors.forename: D J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000382:microbiology* / Q000503:physiopathology; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000503:physiopathology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D005516:Food Microbiology; D011441:Propylthiouracil / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects / Q000503:physiopathology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013956:Antithyroid Agents; D014284:Triiodothyronine; D011441:Propylthiouracil; D013974:Thyroxine