Tick diseases are tricky, as there aren't tests for all of them, and bloodwork is not always consistent. Similarly with Lepto, there are many strains out there, and we only test for something like 6 of them. Tick disease can take years to get to this crisis stage (if that's what this is), so there is always a chance a bite can occur, and there is at least one tick disease that they can get from drinking standing lake/creek water rather than being bit by a tick
I've never had to deal with high calcium levels, so wasn't aware fo the Furosemide connection, thank you. Perfect dosage on the doxy. Do you know the platelet values and the normal range? Are there red spots on the stomach, similar to this pic? http://i47.photobucket.com/albums/f1...attachment.jpg
How is the gum color? When the platelets are dangerously low, pred typically has to be used. However, if there is infection, there is a very tricky balance that is needed so you can eventually get the doxy working. I know that when my boy was on doxy and pred, I had to get the pred real low for the doxy to work well, but it was a bit of a different situation.
When are blood levels going to be checked again? Is your vet a regular vet, or a specialist? I might want a consult with an internal medicine specialist and a speciality clinic right away, sometimes they can diagnose something in 20 minutes that the regular vets completely miss, at least that has always been the case with the internal med guy that I use here.