Submitted to: Veterinary Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/14/2012
Publication Date: 8/17/2012
Citation: Erol, E., Sells, S.F., Williams, N., Kennedy, L., Locke, S.J., Labeda, D.P., Donahue, J.M., Carter, C.N. 2012. An investigation of a recent outbreak of nocardioform placentitis caused abortions in horses. Veterinary Microbiology. 158(2012):425-430. Interpretive Summary: Nocardioform placentitis is an emerging disease in thoroughbred mares almost exclusively in Kentucky which results in major economic losses through late-term spontaneous abortions. The incidence of the disease has varied annually, generally being quite low in recent years, but the 2010-2011 season had a major increase in infected mares. This report demonstrates that the majority of cases were caused by either Crossiella equi or several Amycolatopsis species that had been isolated from infected placentas and characterized in the past decade. There were several other actinobacteria involved in some infections during this foaling season, including strains of two Streptomyces species previously found in equine placentas. The mode of transmission and the reservoir in the environment for the infecting actinobacteria is still unknown but the current data indicates that infection was not related to a specific season. The data presented are useful to horse breeders and veterinary practitioners attempting to manage this economically devastating disease in breeding mares in Kentucky as well as epidemiologists attempting to determine the possible source and route of infection.
Technical Abstract: Nocardioform placentitis caused by Gram-staining positive, branching actinomycetes caused a record number of abortions diagnosed by the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) during 2010-2011 foaling season. In 76 abortion cases, which all were diagnosed as nocardioform placentitis by the pathologists, characteristic slow-growing Gram-stain positive, branching actinomycetes with a musty/soil odor were recovered in high numbers from placental specimens. To determine the type of actinomycetes responsible for the abortions, PCR assays were performed on the Gram-stain positive branching bacteria. The most prominent actinomycetes species detected were Amycolatopsis sp. (37 cases, 48.7%) and Crossiella equi (C. equi) (22 cases, 28.9 %). Six cases (7.9%) contained both Amycolatopsis sp., and C. equi. Ten isolates were unidentified by PCR assays and shown to have high DNA sequence homology to species of the actinomycete genera Streptomyces, Microbacterium, Nocardia, or Allokutzneria as evidenced from 16 rRNA gene sequencing. Nocardioform placentitis-related abortions occurred mostly between December 2010 and April 2011 with exclusivity during the last trimester. Breeding time of aborted pregnancies ranged from March 2010 to July 2011, suggesting that if transmission of the actinomycetes agents occurred during breeding, it was not related to a specific season.