The short answer is NO. Too bad. The American Disability Act (ADA) definition is "Service Animals are defined as dogs that are individually trained to do work or perform tasks for people with disabilities." Sorry, no mention of cats. However cats can be trained as emotional support animals (ESA). My friend has an ESA cat for her depression. When her landlord tried to kick her cat out, my friend's lawyer presented the landlord with the appropriate medical letter, and Ginger the cat was allowed to stay.
Do you have an ESA cat? Do you know anyone who might need their cat trained to be one? Let me know, I would love to help you.