Sorry to hear you haven't found the reason for her fever yet.:(
Years ago I had a dog come down with the same symptoms and the local vet couldn't figure it. We went to the University and this is the first thing they tested him for. Was new back then so I don't blame my vet but it is well known malady today as a sleeper disease.
It is a very serious disease and left untreated for too long can be deadly. When it is caught in the beginning stages there is a very good outcome.
Did you vet suggest this possibility?
Ehrlichia
The clinical manifestations of ehrlichiosis and anaplasmosis are the same. Each is often characterized by sudden high fever
Diagnosis:
Diagnosis is limited by our current ability to test for only two species. Ehrlichia parasites multiply inside host cells, forming large mulberry-shaped clusters called morulae which doctors can sometimes see on blood smears.
The infection still can easily be missed.
Treatment:
The treatment of choice for ehrlichiosis/anaplasmosis is doxycycline, with rifampin recommended in case of treatment failure.
You will be in our prayers tonight that you find out quickly what is ailing Gretchen and for a quick recovery.
