PERITONITIS ASSOCIATED WITH ACTINOBACILLUS-EQUULI IN HORSES - 15 CASES (1982-1992)

Peritonitis attributable to Actinobacillus equuli was diagnosed in IS horses examined at the veterinary center between 1982 and 1992. In 13 horses, historical findings included acute onset of mild to severe sig ns of abdominal pain, lethargy, and inappetence. Two other horses had a history of weight loss for 3 to 6 weeks prior to examination. Diagno sis was based on the physical signs and laboratory findings, including results of peritoneal fluid analysis (gross characteristics, total pr otein, total and differential nucleated cell counts, and morphologic f indings) and culture of A equuli. Actinobacillus equuli was consistent ly susceptible in vitro to penicillin, trimethoprim/sulfadiazine, and aminoglycosides. All horses in the study had marked clinical improveme nt within 24 to 48 hours of commencing antibiotic and supportive treat ment. Antibiotic treatment was continued for variable periods, dependi ng on the horse, but ranged from 5 to 21 days. In 11 horses for which follow-up information was available, long-term response to treatment w as excellent, with horses returning to original activity.