Tritrichomonas foetus – a cause of diarrhea in cats

Diarrhea, especially when it lasts for months or years, can be a challenging problem – particularly in cats living in a shelter or a breeding colony. Tritrichomoniasis is increasingly being recognized as a cause of diarrhea in cats with around 3 in 10 colony cats with diarrhea testing positive. It is less common in pet cats with only 1 in 10 cats with persistent diarrhea testing positive.

Tritrichomonas foetus is a tiny parasite that can live in the large bowel of cats where it may cause inflammation and hence diarrhea. With time, a healthy cat will eliminate the infection or control numbers of parasite to a level where they do not cause signs of disease.

The parasite is passed to other animals when an animal consumes the feces of an infected cat. This can occur when cats are in close contact, for example sharing litter trays and cleaning contaminated fur and feet when grooming. Spread can also occur between a queen and her kittens when grooming. The infection is more common when several cats are kept together such as in a breeding establishment or rescue center. Cats have been shown to be infected after visiting cat shows and pedigree cats seem to be more commonly affected.

The parasite can spread more easily if there is poor litter tray hygiene and over-crowding. Additionally, over-crowding causes stress which can lower a cat’s resistance to many infectious diseases.

Tritrichomonas infection mainly causes diarrhea. Signs of diarrhea are most often seen in young cats and kittens, usually less than 12 months of age. The diarrhea usually affects the large bowel (colitis) with frequent production of semi-formed to liquid, foul-smelling feces. Sometimes there will be fresh blood and/or mucus. With severe diarrhea the anus may become inflamed and painful and, in some cases, cats may drip feces and defecate outside the litter tray. Once clinical signs develop, they may come and go for months but eventually most cases get better without any treatment, although this can take up to 2 years.

Although the diarrhea may be persistent and severe, most affected cats are otherwise well, and do not show significant weight loss or other signs like vomiting. Rarely, very young kittens can become severely unwell. Some cats carry the infection but do not show any signs of disease. These cats may still be able to infect other cats.

If your cat has had diarrhea for more than 48 hours or has a diarrhea that goes away but keeps returning your veterinarian will want to do some tests to find out what is going on. Your veterinarian will ask you to bring in a sample of the diarrhea from your cat for testing. Try and collect a sample that is not contaminated with cat litter as this can affect results. Sometimes it is possible to see the organism in samples of feces or from a swab of the cat’s rectum, but the sample is usually sent to the laboratory for testing. There is a specific laboratory test (a PCR test) that is very sensitive at picking up the presence of the parasite.

No, the infection is specific to cats. However, routine hygiene precautions should be taken when dealing with any cats with diarrhea such as hand washing after handling the cat or the litter tray.

Simple changes to management including feeding either a simple highly digestible diet or a high fiber diet to improve fecal consistency. Good attention to litter tray hygiene, reduction of overcrowding and stress is also helpful. However, this management is a slow process – in one study of infected cats, although some cats improved within 2 months, it took an average of nine months for the diarrhea to stop, with a few cats having diarrhea that continued for more than two years. It is thought that most infected cats continue to shed low levels of the organism in their feces for many months after the diarrhea has stopped so they may still be a risk to other cats in the group in this time.

A drug called ronidazole has been shown to be effective at treating Tritrichomonasis. It is available from veterinary clinics and must be dosed accurately to avoid side-effects (such as trembling or wobbly gait). It is not effective in all cases, as some protozoa may be resistant.

If your cat has diarrhea and is unwell you should see your veterinarian immediately. However, even if your cat remains well and active but has diarrhea that lasts more than 48 hours you should seek advice from your veterinarian. Litter tray hygiene, avoiding stress and overcrowding, isolating new cats may help avoid the spread of this disease.