title: Clinical disease and lung lesions in calves experimentally inoculated with Histophilus somni five days after metaphylactic administration of tildipirosin or tulathromycin.
abstract: OBJECTIVE
  To compare clinical disease and lung lesions in calves experimentally inoculated with Histophilus somni 5 days after metaphylactic administration of tildipirosin or tulathromycin. ANIMALS Twenty-four 3-month-old Holstein and Holstein-crossbreed steers.
  
  
  METHODS
  Calves were randomly allocated to 3 groups of 8 calves. On day 0, calves in group 1 received tildipirosin (4 mg/kg, SC), calves in group 2 received tulathromycin (2.5 mg/kg, SC), and calves in group 3 received isotonic saline (0.9% NaCl) solution (1 mL/45 kg, SC; control). On day 5, calves were inoculated with 10 mL of a solution containing H somni strain 7735 (1.6 × 10(9) CFUs/mL, intrabronchially; challenge). Calves were clinically evaluated on days 5 through 8 and euthanized on day 8. The lungs were grossly evaluated for evidence of pneumonia, and bronchial secretion samples underwent bacteriologic culture.
  
  
  RESULTS
  The mean clinical score for each group was significantly increased 12 hours after challenge, compared with that immediately before challenge, and was significantly lower for tildipirosin-treated calves on days 6, 7, and 8, compared with those for tulathromycin-treated and control calves. The mean percentage of lung consolidation for tildipirosin-treated calves was significantly lower than those for tulathromycin-treated and control calves. Histophilus somni was isolated from the bronchial secretions of some tulathromycin-treated and control calves but was not isolated from tildipirosin-treated calves.
  
  
  CONCLUSIONS
  Results indicated that metaphylactic administration of tildipirosin to calves 5 days prior to H somni challenge prevented subsequent culture of the pathogen from bronchial secretions and was more effective in minimizing clinical disease and lung lesions than was metaphylactic administration of tulathromycin.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Confer
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Snider
authors.forename: Jared D
authors.initials: JD
authors.lastname: Taylor
authors.forename: Marie
authors.initials: M
authors.lastname: Montelongo
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Sorensen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000382:microbiology / Q000473:pathology; D004187:Disaccharides / Q000008:administration & dosage / Q000627:therapeutic use*; D006571:Heterocyclic Compounds / Q000008:administration & dosage / Q000627:therapeutic use*; D015661:Pasteurellaceae; D016871:Pasteurellaceae Infections / Q000188:drug therapy / Q000662:veterinary*; D018410:Pneumonia, Bacterial / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*; D016896:Treatment Outcome; D015645:Tylosin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use; D018942:Macrolides
chemical_list: D004187:Disaccharides; D006571:Heterocyclic Compounds; D015645:Tylosin; C576258:20,23-dipiperidinyl-mycaminosyl-tylonolide; C485204:tulathromycin; D018942:Macrolides