Helen, I have copied and pasted the below info from the bengal forum: It talks about Bengals but applies to any cat
Some cats can be prone to sensitive tummies, and diarrhoea is a problem for numerous Bengal owners who join this forum asking for advice. Pet owners often have to spend time trying out different diets in the hope of rectifying the problem which can take weeks or months - if indeed the diarrhoea problem is diet-related.
Giardia and coccidia are the more common causes of persistent diarrhoea in cats which can be detected through faecal testing.
Tritrichomonas foetus more commonly known as ‘TF’ is a single-celled parasite only recently found in felines. Symptoms can include diarrhoea with or without blood present and with a particular ‘foul’ smelling odour.
Cats can carry this parasite for years without showing any symptoms.
It is becoming more common in the Bengal breed.
Giardia is often misdiagnosed for TF.
Bengals don’t have to suffer with this condition; it is treatable. Many people and some breeders are still unaware of TF. Some vets will be unaware of TF in Bengals and won’t offer testing.
Below is a link which provides comprehensive and invaluable information on TF.
http://www.fabcats.org/breeders/infosheets/tritrichomonas.html PLEASE, if your Bengal is suffering from chronic diarrhoea ask your vet to test for TF. Our cats need not suffer from this condition; it can be detected and it can be treated