Q. Cat has diarrhea, the cat is stray that was emaciated and very hungry, and was seen by a vet at the pet shelter, but her diarrhea has continued
DAVID ELBEZE, DVM, MRCVS
A. Chronic diarrhea in stray cat could be caused by many reasons. First two common infections in stray cats are FIV and FELV. Both affecting the immune system and can cause diarrhea and emaciation.
FIP is another viral chronic uncurable disease that could cause these symptoms.
Intestinal parasites need to be ruled out as well by deworming her. Gastro intestinal food should be given to try and rule out food intolerance.
The viral diseases need to be tested first, a simple blood test will rule out or confirm one of them. Treatment of those diseases is supportive only.
DESTINI R. HOLLOWAY, DVM
A. Stray cats can pretty nasty parasitic infections. I would check to see if the vet ran a fecal examination + a Giardia test. Both of these can pick up on many parasites that can cause persistent diarrhea. However, if these tests were already done and were negative, then additional testing may be needed to find other not so common causes of diarrhea like the one ran by Idexx. Http://www.idexx.com.au/pdf/en_au/smallanimal/reference-laboratories/diagnostic-updates/realpcr-canine-feline-diarrhea-panels.pdf
Any pet with diarrhea should be on a broad-spectrum dewormer, probiotics and potentially and antibiotic for treatment regardless of any of the tests mentioned above.
I would suggest going back to the vet for additional treatment and these additional tests if not done already.