A young woman who was recently hiking in the mountains and discovered a tick on her torso has a fever that came on quite suddenly. She has no rash, but she develops leukopenia. What disease is she most likely to have contracted?

The disease most likely to be contracted is Anaplasmosis.

Explanation:

It's caused by the bacterium Anaplasma phagocytophilum found in the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus).

These bacteria are spread through these tick bites causing anaplasmosis that leads to fever, headache, chills, and muscle aches