system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 45-year-old man presents to the physician with complaints of fever with rigors, headache, malaise, muscle pains, nausea, vomiting, and decreased appetite for the past 3 days. He informs the physician that he had been backpacking on the Appalachian Trail in the woods of Georgia in the month of June, 2 weeks ago, and had been bitten by a tick there. His temperature is 39.0°C (102.3°F), pulse is 94/min, respirations are 18/min, and blood pressure is 126/82 mm Hg. His physical exam does not reveal any significant abnormality except for mild splenomegaly. Laboratory studies show:
Total white blood cell count 3,700/mm3 (3.7 x 109/L)
Differential count  
Neutrophils 85%
Lymphocytes 12%
Monocytes 2%
Eosinophils 1%
Basophils 0%
Platelet count 88,000/mm3 (95 x 109/L)
Serum alanine aminotransferase 140 IU/L
Serum aspartate aminotransferase 80 IU/L
Microscopic examination of a peripheral blood smear stained with Wright-Giemsa stain shows the presence of morulae in the cytoplasm of leukocytes. In addition to drugs for symptomatic relief, what is the most appropriate initial step in the treatment of this patient?
assistant
Doxycycline