Frequency of Corynebacterium pseudotuberculosis Infection in Horses Across the United States During a 10-Year Period

Corynebacterium pseudotuberculosis infection in horses is increasing and occurs throughout the United States. Further studies to determine changes in annual incidence and to identify potential changing climatic conditions or vector populations associated with transmission of infection are warranted. Authors’ addresses: The Department of Medicine and Epidemiology (Spier), the William R. Pritchard Veterinary Medical Teaching Hospital (Kilcoyne), University of California, Davis, CA 95616; the Veterinary Diagnostic Laboratory, University of Kentucky, Lexington, KY 40511 (Carter, Smith); and the Department of Veterinary Pathobiology (Swinford) and the Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences (Cohen), College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843; e-mail: [email protected].

1. Introduction

Corynebacterium pseudotuberculosis causes various clinical forms of infection, including external abscesses in the pectoral or ventral abdominal area, internal abscessation, or infection of the limbs. The purpose of this study was to examine the occurrence of C. pseudotuberculosis infection throughout the United States over a 10-year period.

2. Materials and Methods

State veterinary diagnostic laboratories in the United States were solicited to participate in a crosssectional study. Data from 2237 horses culturepositive for C. pseudotuberculosis identified by 15 veterinary diagnostic laboratories were collected. Data requested included number of cases of C. pseudotuberculosis infection in horses seen per year, geographical regions from which the sample was obtained, month and year of sample submission, breed and age of horses, and category of clinical presentation (i.e., internal infection, external infection, or ulcerative lymphangitis). 

3. Results and Discussion

Fifteen laboratories provided data from 23 states. The proportion of cases during 2011 and 2012 (54%; 1213/2237) was significantly (P < 0.0001) greater than that for period from 2003 to 2010 (46%; 1024/2237). C. pseudotuberculosis was recovered from horses in states where disease has not been previously recognized as endemic. Horses were identified year-round. No significant association between the clinical form of disease and age or breed was observed.

Acknowledgments

The authors would like to acknowledge the state diagnostic laboratories for collecting and contributing data to the study.

Conflict of Interest

The Authors would like to thank Zoetis for funding and declare no conflicts of interest.