Efficacy of tulathromycin for treatment of cattle with acute ocular Moraxella bovis infections.
OBJECTIVE
To evaluate the clinical efficacy of a single injection of tulathromycin, compared with saline (0.9% NaCl) solution-treated control calves, for treatment of induced infectious bovine keratoconjunctivitis in calves.


METHODS
Clinical trial.


METHODS
30 Holstein bull calves ranging from 5 to 6 months old and 75 to 200 kg (165 to 440 lb) with no history of Moraxella bovis infections, no history of M bovis vaccination, and negative results for M bovis on 3 consecutive ocular bacterial cultures.


METHODS
Both eyes of each calf were infected with 1 X 10(10) colony-forming units of piliated M bovis for 3 consecutive days prior to the trial. On day 0, ocular lesion scores were determined for each calf and the calves were weighed and assigned to a treatment (2.5 mg/kg [1.14 mg/lb] of body weight, SC) or control group according to a stratified random allocation based on weight and lesion score. Eyes were stained with fluorescein and photographed daily to record healing. Eyes were evaluated bacteriologically for M bovis on days 0 to 6 and at 3-day intervals thereafter.


RESULTS
Median time to ulcer resolution in calves treated with tulathromycin was 9.1 days. More than 50% of control calves still had ulcers at the end of the trial (21 days). Moraxella sp was isolated less often from the eyes of treated calves than from the control calves. By day 10, the treated calves had lower ocular lesion scores than control calves.


CONCLUSIONS
A single dose of tulathromycin (SC) was an effective treatment of calves with experimentally induced infectious bovine keratoconjunctivitis. The long serum half-life of tulathromycin, along with the results of this trial, suggests that tulathromycin may be a rational choice as a single-injection treatment for infectious bovine keratoconjunctivitis.
Lane
V Michael
VM
Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, 95616-8734, USA.
George
Lisle W
LW
Cleaver
Dawn M
DM
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000473:pathology; D004187:Disaccharides / Q000627:therapeutic use*; D006571:Heterocyclic Compounds / Q000627:therapeutic use*; D007639:Keratoconjunctivitis, Infectious / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D016955:Moraxella bovis / Q000187:drug effects; D045828:Moraxellaceae Infections / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*; D013997:Time Factors; D016896:Treatment Outcome; D018942:Macrolides
D000900:Anti-Bacterial Agents; D004187:Disaccharides; D006571:Heterocyclic Compounds; C485204:tulathromycin; D018942:Macrolides