Effectiveness of enrofloxacin for the treatment of experimentally-induced bovine anaplasmosis.

Four groups of six Holstein calves were inoculated with 3.6 × 10(7) erythrocytes parasitized with Anaplasma marginale. The criteria for treatment of calves were increasing A. marginale rickettsemia and 30% reduction of baseline packed cell volume (PCV) of each animal. Group 1 (G1) received 7.5 mg.kg(-1) of enrofloxacin in a single dose; Group 2 (G2) 7.5 mg.kg(-1) of enrofloxacin twice every three days; Group 3 (G3) 20 mg.kg(-1) of long-acting oxytetracycline in a single dose; and Group 4 (G4) a single dose of PBS. Physical examinations, blood smears and PCV were performed daily. On day treatment, G1, G2 and G3 animals had a mean rickettsemia of 17, 23 and 12%, respectively. At 2 days after treatment (DAT) G1 and G2 animals showed a significant reduction of rickettsemia (p < 0.05) compared to G3. G3 animals had high rates of rickettsemia in the first 2 DAT and a slow decrease until stabilization on 9 DAT. The mean PCV in G1 and G2 increased and stabilized after 7 and 8 DAT, respectively. PCV stabilization was achieved in G3 at 13 DAT. Both enrofloxacin and oxytetracycline were effective for the treatment of anaplasmosis, but enrofloxacin was faster reduction of rickettsemia and PCV recuperation (p < 0.05) compared to oxytetracycline.