Efficacy of florfenicol in the treatment of experimentally induced infectious bovine keratoconjunctivitis.
OBJECTIVE
To evaluate efficacy of florfenicol in an induced model of infectious bovine keratoconjunctivitis, using a blinded randomized, controlled trial.


METHODS
48 male Holstein calves, 2 to 4 months old.


METHODS
Moraxella bovis infection was induced in all calves. When corneal ulcers developed, each calf was assigned randomly to 1 of 3 treatment groups, using a block design determined by corneal ulcer size (day 0). Calves were treated with florfenicol (20 mg/kg of body weight, IM) on days 0 and 2 (IM group; n = 16). Calves of a second group received a single dose of florfenicol (40 mg/kg, SC) on day 0 (SC group; n = 16). The third group of calves was not treated (control group; n = 16). Corneal ulcers were photographed, and each calf was assessed for 30 days after treatment for 10 clinical signs of infection. Corneal ulcer surface areas were measured, and clinical scores were calculated. Ocular secretions for microbiologic culture were obtained weekly from each eye.


RESULTS
A Cox regression model indicated that, after adjustment for initial ulcer size, healing rates were 6.2 and 4.8 times greater in calves of the IM and SC groups, respectively, compared with the control group. Clinical scores and surface area measurements for treatment groups were significantly smaller than those for controls during posttreatment weeks 1 through 4. From day 8 through day 29, M bovis was isolated from ocular secretions of 14 of 16 control calves and 1 of 32 treated calves.


CONCLUSIONS
Parenterally administered florfenicol reduces corneal ulcer healing time, lessens clinical severity, and reduces the amount of bacterial shedding from calves infected with M bovis.
Dueger
E L
EL
Department of Veterinary Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
Angelos
J A
JA
Cosgrove
S
S
Johnson
J
J
George
L W
LW
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000592:standards* / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D003287:Contrast Media / Q000737:chemistry; D003320:Corneal Ulcer / Q000188:drug therapy; D019793:Fluorescein / Q000737:chemistry; D007273:Injections, Intramuscular / Q000662:veterinary; D007279:Injections, Subcutaneous / Q000662:veterinary; D007639:Keratoconjunctivitis, Infectious / Q000188:drug therapy*; D008297:Male; D016955:Moraxella bovis / Q000187:drug effects; D016870:Neisseriaceae Infections / Q000188:drug therapy / Q000662:veterinary*; D010781:Photography / Q000662:veterinary; D016016:Proportional Hazards Models; D013839:Thiamphenicol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000592:standards / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D003287:Contrast Media; C035534:florfenicol; D013839:Thiamphenicol; D019793:Fluorescein