[idlewords]

My mom just got Lyme disease with similar alarming symptoms, and has responded rapidly to antibiotics. I'm glad your father got the diagnosis in time.

One thing I learned in the process is that the bullseye rash is often just a broad, flat red area, and in some people (as you point out) doesn't show at all. Any summertime flulike symptoms in tick country should lead you to suspect Lyme disease (or the group of similar related tick-borne infections).