Efficacy of difloxacin in calves experimentally infected with Mannheimia haemolytica.
OBJECTIVE
To determine the efficacy of difloxacin, a novel fluoroquinolone antibiotic, in calves experimentally infected with Mannheimia haemolytica (formerly Pasteurella haemolytica).


METHODS
Seventy-two 3-month-old Holstein calves.


METHODS
Calves were inoculated with M haemolytica intratracheally; after they developed clinical signs of pneumonic pasteurellosis, they were randomly assigned to 1 of 6 groups (n = 12/group). Calves in each group were treated with 10% difloxacin (2.5 or 5 mg/kg of body weight), 5% difloxacin (2.5 or 5 mg/kg), enrofloxacin (5 mg/kg), or saline (0.9% NaCl) solution (control group), once daily for 5 days, and clinical signs were scored daily. On day 15, calves were euthanatized, and the percentage of diseased lung tissue was calculated. Swab specimens of the lungs were submitted for bacterial culture.


RESULTS
Mortality rate and percentage of diseased lung tissue were significantly higher and cure rate and average daily gain were significantly lower for control calves, compared with calves in the treatment groups; however, no significant differences were found among treatment groups. Mannheimia haemolytica was isolated from the lungs of 10 control calves and from at least 2 calves in each of the treatment groups.


CONCLUSIONS
Results suggest that difloxacin and enrofloxacin were equally effective for treatment of calves with experimentally induced pneumonic pasteurellosis. However, treatment of infected calves with difloxacin or enrofloxacin may not eliminate the organism.
Olchowy
T W
TW
Fort Dodge Animal Health, Princeton, NJ 08543-0400, USA.
TerHune
T N
TN
Herrick
R L
RL
D000818:Animals; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D001831:Body Temperature; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000382:microbiology; D002939:Ciprofloxacin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000592:standards / Q000627:therapeutic use; D000077422:Enrofloxacin; D024841:Fluoroquinolones; D008168:Lung / Q000382:microbiology / Q000473:pathology; D008297:Male; D016978:Mannheimia haemolytica / Q000187:drug effects* / Q000254:growth & development; D010326:Pasteurella Infections / Q000188:drug therapy / Q000662:veterinary*; D015363:Quinolones / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use; D011897:Random Allocation; D015430:Weight Gain
D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D015363:Quinolones; D000077422:Enrofloxacin; D002939:Ciprofloxacin; C047225:difloxacin