Abstract:
Three bacteria extensively acknowledged as venereal pathogens with the potential to
induce endometritis include Taylorella equigenitalis, the causative agent of contagious
equine metritis (CEM), specific strains of Pseudomonas aeruginosa, and certain capsule
types of Klebsiella pneumoniae. The United Kingdom's Horserace Betting Levy Board
recommends pre-breeding screening for these bacteria in their International Codes of
Practice and >20 000 samples are tested per annum in the United Kingdom alone.
While the pathogenesis and regulatory importance of CEM are well established, an
evaluation of the literature pertaining to venereal transmission of P. aeruginosa and
K. pneumoniae was lacking. The aim of this review was to evaluate published literature
and determine the significance of P. aeruginosa and K. pneumoniae as venereal pathogens in horses. Literature definitively demonstrating venereal transmission was not
available. Instead, application of molecular typing methods suggested that common
environmental sources of contamination, such as water, or fomites be considered as
modes of transmission. The presence of organisms with pathogenic potential on a
horse's external genitalia did not predict venereal transmission with resultant endometritis and reduced fertility. These findings may prompt further investigation using
molecular technologies to confirm or exclude venereal spread and investigation of
alternative mechanisms of transmission are indicated.
