Contagious Equine Metritis: Efficacy of US post-entry testing protocols for identifying carrier stallions and mares

Abstract

tissue in 2002. In 2003, three species of Amycolatopsis and in 2009 two species of Streptomyces were identified in association with NPA cases. Amycolatopsis spp. (48.7%) and Crossiella equi (28.9%) were the most prominent nocardioforms identified in a recent abortion outbreak. This infection leads to late abortions, stillbirths and premature foaling. Premature foals sometimes die shortly after birth. Themode of transmission of this syndrome is not known. To date, nocardioform Actinomycetes have only been isolated from placental tissue. Most reported cases are from central Kentucky (Figure 1) but cases have also been diagnosed in Florida, Italy, and South Africa. In the 2010-2011 equine reproductive season, our Lexington laboratory diagnosed 118 cases of NPA by culture and PCR. Due to the high incidence of NPA that season, a farm-level study was conducted to identify possible risk factors for NPA. A total of 148 horse farms were included in a survey (98 affected, 50 farms unaffected). In total, 8075 mares were at risk on all farms with 429mares diagnosedwith NPA. On average, four mares were affectedper farm.Datawere analysedusing chi-squared,Wilcoxon rank-sum tests, and logistic regression analysis using S-PLUS. Farm acreage,mare numbers, and higher density on affected farmswere significantly and positively associated with NPA. Longer grazing times during January-March administration of progesterone prebreeding, HCG post-breeding, and NSAIDs were significantly and negatively associated with NPA. A study at the University of Kentucky attempted to induce NPA in pregnant and non-pregnant mares via intrauterine, oral, and intranasopharyngeal inoculation of Crosiella equi. However, these attempts did not result in infections or abortions.