Testing Is Less than Reliable. Fear Not for the Positive Cat-Most Never Get Sick.
Recently I adopted a wonderful cat from animal control who had developed an upper respiratory infection. All the blood work came back perfect and negative for Felv and FIV. The corona virus came back as a high titer 1:1600. I was advised that more than likely, the cat does not have FIP but, of course, no guarantee. He is almost over the respiratory infection.
I have another cat at home who tested 1:1600 three consecutive times for corona virus. She has continued to be healthy. I have kept the new cat in my garage. I do not want to subject my cat to any unneeded risk. I am considering placing the new cat with a rescue group.
Feline Infectious Peritonitis (FIP) is a horrible viral disease that is always fatal. The truth is that there is a lot of FIP out there, but relatively few cats actually get sick. Symptoms include weight loss, poor appetite, and high fever. Many have dull hair coats and thick fluid accumulations in the chest and/or abdomen. The eyes, kidneys, liver, and brain can become involved too. There are a few treatments, but we can only buy time for these sick kitties.
There are two types of FIP virus, each with a variety of strains. There are other members of the corona virus family too, but only some of them cause disease. Several tests are available but none are truly specific; past exposure to any corona virus can give a positive result. Since many infected cats have vague symptoms, an accurate diagnosis can be difficult.
You have two healthy cats who have flunked their tests, so neither is a threat to the other. You probably have nothing to worry about; fewer than 10% of positive cats ever get the disease. Should you keep your wonderful new cat? I would. He sounds great. Nothing is for sure, but life is short. Live for today.