Efficacy of Minocycline in Naturally Occurring Nonacute Ehrlichia canis Infection in Dogs

BACKGROUND: Minocycline has been used in the treatment of Ehrlichia canis infection in dogs as an alternative to doxycycline, the recommended treatment. However, efficacy of this alternative therapy is unknown. OBJECTIVE: To assess the efficacy of minocycline in the treatment of natural occurring E. canis infection in dogs. ANIMALS: Ten privately owned dogs of mixed breed positive for E. canis by blood PCR. METHODS: Prospective, randomized clinical study. Dogs positive for E. canis by PCR were housed in a kennel environment and randomly allocated to receive doxycycline 10 mg/kg bodyweight PO once daily (“gold standard” control group) or minocycline (extralabel) 10 mg/kg bodyweight PO twice daily (treatment test group) for 28 days. Blood, analyzed by PCR to determine the presence or absence of E. canis DNA, was collected weekly during treatment starting on the first day of treatment and including through day 35, 7 days after the last treatment. RESULTS: In both groups, one dog tested negative after 7 days of treatment. For the doxycycline group, the latest time to a negative PCR test was after 3 weeks of treatment. For the minocycline group, the latest time was on day 28 of treatment. All dogs tested negative 7 days after the end of treatment. CONCLUSION AND CLINICAL IMPORTANCE: Minocycline can be an effective alternative to doxycycline for clearing E. canis from the blood in nonacute infections.