AN OUTBREAK OF RESPIRATORY-DISEASE IN HORSES ASSOCIATED WITH MYCOPLASMA-FELIS INFECTION

Lower respiratory tract disease developed in a group of racehorses in training between two and six years of age, Disease was observed in 22 of 25 horses for which full records were available, Seroconversion to Mycoplasma felis was demonstrated by indirect hemagglutination assay i n 19 of 22 paired sera and high titres (greater than or equal to 64) w ere found in convalescent sera from the three remaining horses. Eviden ce of respiratory viral infection was confined to seraconversions to e quine herpes-virus-4 in two of the horses, Tracheal wash samples, take n from four horses with visibly increased tracheal mucopus, contained more than 10(4) colony forming units/ml M felis and high proportions o f neutrophils. This is tile first description of an outbreak of lower respiratory tract disease in horses in training associated with M feli s infection.