Our poor little cat is only 9 months and the vet is almost positive from blood tests that he has this. He's very depressed, lethargic, not eating, fur looks dull and has a bloated abdomen. He looks old. Vet says nothing they can do 
, he will give me some anti-histamine tablets tomorrow that will try and stimulate his appetite.
We've got another kitten from the same litter and apparently it's highly infectious so now we're worried she might get it as well (she is full of beans at the moment). These were rescue cats so we don't know much of their history, possible he had the virus from birth.
Has anyone come across this? do we isolate the sickly cat from the healthy one?
DS is going to be so upset if we have to put Leo down, as we only put down our elderly cat at Christmas (got these 2 in Jan).