When you think of tick-born illnesses, Lyme and Rocky Mountain Spotted Fever are usually high on the radar. Ehrlichia should be as well.
More common in the Southeastern United States, Ehrlichia is transmitted by the Lone-Star tick. It causes a triad of leukopenia, thrombocytopenia, and elevated transaminase levels. Other symptoms include non-specific symptoms such as myalgias, fever, GI symptoms, headache.
If you suspect Ehrlichia, send your studies, but also start Doxycycline 100 mg twice daily empirically for at least 5 days, or 3 days after fever ends. You can also stop Doxy if your studies come back negative and you have another source of pathology.