Dr. Balsama

Dr.Tail Vet

The symptoms you've described in your American Curl cat, particularly the presence of bloody or black diarrhea that occurs episodically, can be indicative of several underlying health issues. Diarrhea of this nature can be caused by a variety of factors including but not limited to intestinal parasites, infections, inflammatory bowel disease, certain types of cancer, or even a reaction to something ingested that could be toxic or not agreeable with your cat's system.
Given the episodic nature of the diarrhea, it's possible that there is a specific trigger causing these bouts. It could be related to diet, stress, or exposure to a particular substance. Since you've mentioned that there are also behavioral changes, it's important to consider whether these are a cause or a result of the gastrointestinal symptoms. Cats can display changes in behavior when they're not feeling well, and gastrointestinal discomfort can certainly lead to such changes.