I had 2 absolutely stunning full breed British Shorthair kittens. From from different owners and both females. Not only did they become best of friends and inseparable, they became sisters. Cuddles for 5 months old and the other kitten 6 months. Unfortunately today, 2 days after seeing symptoms for a potential FIP, for Cuddles who is the younger one, her condition deteriorated rapidly and went from a healthy cat to being unable to move with only 5% of red blood cells. We have had to put her down today in order to take away her suffering.  We cannot even grief for her as now we are truly and whole heartedly concerned for the other kitten. Has she got it? The research suggests its contagious and spread through the sharing of litter tray; which they both did. Truly heartbreaking disease.