This article is from the Feline Infectious Peritonitis FAQ, posted to rec.pets.cats newsgroup. Maintained by Erin Miller with numerous contributions by others.
I have a lot of cats, what can I do to keep the risk of FIP down? Limit the number of new cats and isolate each for at least one month, preferably two. I know it sounds like a long period of time, but consider the alternatives! You could lose every cat in your household. During the one month's time period, make sure you watch carefully for signs of illness. You should give the coronavirus titer test at the beginning and the end of the quarantine period, and the titer should decrease over that time period. Scoop the litter box daily, discard the rest of the litter weekly and disinfect the boxes with a 1:32 solution of bleach. The area around the boxes should be swept and disinfected, there should be at least one box for every two cats in the household. Again, weekly discarding of the scoopable litter may seem like a waste, but so far the ONLY thing the sources agree upon with regard to transmission is that it is definitely transmitted through the feces, if nothing else. In the words of one breeder: "It cost me approximately $3,000 in veterinary and laboratory services to diagnose the incidence of FIP in my cattery, test and retest (and retest) all of my cats. Believe me it is FAR less expensive to discard the litter" (Polli, p. 81). If your cats have long hair and fecal matter tends to stick to the britches, this hair should be kept clipped short. Change food and water daily, disinfect the bowls weekly. Do not mix the bowls all around the house, keep the same set of bowls with the same cats, and keep the same set of litter boxes with the same cats.