Sadly, a close friend of mine had a dog that died from a tick-borne disease. I don’t recall exactly which disease, but it involves initial symptoms that are fairly minor and easily mis-diagnosed. Those initial symptoms resolve spontaneously, but then the pathogen migrates across the blood-brain barrier and the disease re-emerges in the form of neurological symptoms. If it is treated with the correct antibiotics in the early stage, it is usually treatable. But once the neurological symptoms appear, treatment is extremely difficult, involving hospitalization and high doses of IV antibiotics, which are not always effective.