Giardia is a commonly recognised cause of gastrointestinal upset in cats in Hong Kong. Dr. Carla and colleagues from Peace Avenue Veterinary Hospital ,collected evidence for a study which suggested Tritrichomonas , should also be considered as a cause of diarrhoea , in all cats , but particularly young purebred males. Tritrichomonas can be diagnosed by looking at fresh stool under the microscope or by PCR testing. The study also found that co-infections with giardia are not uncommon.
You can read Dr. Carla’s work here