Four groups of six Holstein calves were inoculated with 3.6 × 107
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