title: Frequency of Corynebacterium pseudotuberculosis infection in horses across the United States during a 10-year period.
abstract: OBJECTIVE
  To quantify the number of horses with Corynebacterium pseudotuberculosis infection identified in the United States from January 2003 through December 2012.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  State veterinary diagnostic laboratory records of 2,237 C pseudotuberculosis culture-positive samples from horses.
  
  
  METHODS
  44 state veterinary diagnostic laboratories throughout the United States were invited by mail to participate in the study. Data requested included the number of C pseudotuberculosis culture-positive samples from horses identified per year, geographic location from which the C pseudotuberculosis culture-positive sample was submitted, month and year of sample submission, breed and age of horses, and category of clinical manifestation (ie, internal infection, external infection, or ulcerative lymphangitis).
  
  
  RESULTS
  Of the 44 invited laboratories, 15 agreed to participate and provided data on affected horses from 23 states. The proportion of C pseudotuberculosis culture-positive samples submitted during 2011 through 2012 (1,213/2,237 [54%]) was significantly greater than that for the period from 2003 through 2010 (1,024/2,237 [46%]). Corynebacterium pseudotuberculosis was recovered from horses in states where the disease has not been previously recognized as endemic. Affected horses were identified year-round. The greatest proportion of C pseudotuberculosis culture-positive samples was identified during November, December, and January (789/2,237 [35%]). No significant association between the clinical form of disease and age or breed of horse was observed.
  
  
  CONCLUSIONS
  The occurrence of C pseudotuberculosis infection in horses increased during the 10-year period, and affected horses were identified throughout the United States. Further studies to determine changes in annual incidence and to identify potential changing climatic conditions or vector populations associated with disease transmission are warranted to help control the occurrence and spread of C pseudotuberculosis infection in horses.
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kilcoyne
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Spier
authors.forename: Craig N
authors.initials: CN
authors.lastname: Carter
authors.forename: Jacqueline L
authors.initials: JL
authors.lastname: Smith
authors.forename: Amy K
authors.initials: AK
authors.lastname: Swinford
authors.forename: Noah D
authors.initials: ND
authors.lastname: Cohen
mesh_terms: D000818:Animals; D003354:Corynebacterium Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D016925:Corynebacterium pseudotuberculosis / Q000302:isolation & purification*; D005260:Female; D006734:Horse Diseases / Q000453:epidemiology / Q000382:microbiology*; D006736:Horses; D008297:Male; D013997:Time Factors; D014481:United States / Q000453:epidemiology