how does anaplasmosis in dogs present clinically and what is the recommended treatment duration?

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Canine anaplasmosis most commonly presents as a subclinical or mild febrile illness, with the most frequent clinical signs being fever, lethargy, inappetence, lymphadenomegaly, splenomegaly, and bleeding tendencies including petechiae and ecchymoses.15 Dogs infected with Anaplasma phagocytophilum can additionally develop lameness and inflammatory polyarthropathy.15 Vomiting, diarrhea, uveitis, hepatomegaly, and polyarthritis have also been reported.45 Common laboratory abnormalities include thrombocytopenia, anemia, neutropenia, and lymphopenia.45 Morulae within neutrophils on peripheral blood smear are specific for active infection when identified, though cytology is an insensitive diagnostic method.5 Increased liver enzyme activity is a frequent concurrent finding.3 Atypical but documented presentations include cavitary effusions. Pericardial effusion causing cardiac tamponade has been confirmed as a manifestation of A. phagocytophilum infection in dogs, with morulae found within neutrophils in the pericardial fluid and PCR confirmation from both pericardial fluid and blood.3 Myocardial damage is also reported.2 Doxycycline is the treatment of choice, dosed at either 5 mg/kg PO q12h or 10 mg/kg PO q24h for four weeks.2 Dogs treated during the acute phase typically improve within 24–48 hours of initiating therapy.2 Most patients recover within 1–2 weeks, though doxycycline's therapeutic effects develop over several days to weeks.2 The optimal treatment duration has not been definitively established; while a four-week course is standard, the minimum effective duration remains undefined.2 In the confirmed pericardial effusion case, doxycycline at 5 mg/kg PO q12h for 14 days combined with pericardiocentesis resulted in complete resolution with no recurrence of effusion on echocardiogram at one-month recheck.3 Alternative antibiotics with documented efficacy against A. phagocytophilum in dogs include orbifloxacin (5 mg/kg SC on day 1, then PO q24h for two weeks) and en