title: A randomized controlled field trial of a novel trimethoprim-sulfadiazine oral suspension for treatment of Streptococcus equi subsp zooepidemicus infection of the lower respiratory tract in horses.
abstract: OBJECTIVE
  To evaluate the effectiveness of a novel trimethoprim-sulfadiazine oral suspension for the treatment of naturally acquired Streptococcus equi subsp zooepidemicus infection in horses.
  
  
  METHODS
  Randomized, controlled field trial.
  
  
  METHODS
  180 horses with S equi subsp zooepidemicus infection.
  
  
  METHODS
  Horses with lower respiratory tract infections caused by S equi subsp zooepidemicus were treated with a new formulation of combined trimethoprim-sulfadiazine oral suspension at a dosage of 24 mg/kg (10.9 mg/lb) twice daily for 10 days (treatment group) or with an equivalent volume of saline (0.9% NaCl) solution (placebo group). Response to treatment, including clinical signs and fecal consistency scores, was assessed twice daily. Any adverse effects were recorded. The primary outcome variable was clinical response; the secondary outcome variable was eradication of S equi subsp zooepidemicus on study day 17 as determined by bacteriologic culture of repeated transtracheal-wash specimens.
  
  
  RESULTS
  Of the 119 horses allocated to the treatment group, 69 (58%) had a positive clinical response. A significantly smaller proportion of horses in the placebo group (9/61 [15%]) had a positive clinical response. By day 5, 25 of 61 (41%) placebo horses had been withdrawn from the study because of negative clinical response, compared with only 10 of 119 (8.4%) treated horses. By day 10, 28 of 61 (46%) placebo horses had been withdrawn because of negative clinical response, compared with only 13 of 119 (11%) treated horses. There were few adverse events associated with the trimethoprim-sulfadiazine suspension. There were no significant differences in fecal consistency scores between treatment and placebo groups.
  
  
  CONCLUSIONS
  The new oral suspension administered at 24 mg/kg twice daily effectively treated the clinical signs of S equi subsp zooepidemicus lower respiratory infection in horses and eliminated the organism from the respiratory tract. Adverse effects were minimal.
authors.forename: Scott R
authors.initials: SR
authors.lastname: McClure
authors.forename: Robbin
authors.initials: R
authors.lastname: Koenig
authors.forename: Peggy Anne
authors.initials: PA
authors.lastname: Hawkins
mesh_terms: D000284:Administration, Oral; D000818:Animals; D004338:Drug Combinations; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy* / Q000382:microbiology; D006736:Horses; D008297:Male; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D018502:Streptococcus equi; D013411:Sulfadiazine / Q000008:administration & dosage / Q000627:therapeutic use*; D013535:Suspensions; D014295:Trimethoprim / Q000008:administration & dosage / Q000627:therapeutic use*; D000096926:Benzenesulfonamides
chemical_list: D004338:Drug Combinations; D013411:Sulfadiazine; D013535:Suspensions; D014295:Trimethoprim; C024873:sulfadiazine, trimethoprim drug combination; D000096926:Benzenesulfonamides