I am so worried. Gave my roughly 11 year old FIV positive cat the Merial Purevax 3-year rabies shot yesterday. Right after the vet left my cat hid and slept for a few hours, then transferred to the couch and slept a few more hours. When he woke up about 10 hours after the shot, he slipped off the couch trying to get down, he was so weak. He walked to the litter box like he weighed 1000 pounds. Didn't eat dinner, went upstairs and laid for hours just staring in the distance. Finally went to sleep. I woke up and he purred when I pet him (usually we snuggle multiple times a day). He has had all his meals from "bed" today... I deliver his wet food to where he is lying and he eats it without getting up. He is going to the bathroom and walking slowly around from spot to spot. I am coming up on 36 hours and he is still lethargic. Worried sick.