Marla is an older cat who has recently had the displeasure of becoming a frequent visitor to our practice. She was adopted not long ago from an animal shelter and now lives with a lovely woman who thankfully has a lot of patience! Marla first came to see us because she had developed diarrhoea and a red, irritated rear end. She had a type of diarrhoea called ‘colitis’ (which simply means inflammation of the large intestine or colon), that caused her to strain frequently to produce small amounts of sometimes bloody stool. She was treated with antibiotics and her diet was changed to something that was bland and easy to digest, and although sometimes her symptoms seemed to improve a little they continued. A standard stool sample was run but this was negative for all worms and harmful bacteria. After nearly a month of problems and after trying every routine treatment out there, we decided to try one last and wouldn’t you know, it came back positive! Marla had developed an infection of Tritrichomonas foetus (which I’ll call T. foetus from now on), a previously rare but becoming increasingly common infection in cats. Recent studies have shown that the infection is even more common than we think, so if you think your cat may be affected it might be worth looking into! What is T. foetus?
- T. foetus is a single-celled protozoal parasite (bigger than a bacteria but smaller than a mite, with a very clever membrane and a few tails that help it move around). The infection was originally found in cattle, but it’s cats that have been more of a concern recently.
- Most affected cats are less than 1 year old, but as in Marla’s case, it can affect cats of any age.
- Purebred kittens from breeding colonies or cats in shelters or multi-cat households are more likely to get the disease.
- Up to 30% of cats in the UK and US may test positive for the organism, but not all those that carry the disease will show symptoms.
- Semi-formed to liquid faeces (diarrhoea)
- Blood or mucus in the faeces
- Straining or painful defecation (may lead to howling in the litter tray)
- Increased frequency of defecation (more frequent trips out the cat flap)
- Inflamed and painful anus (may lead to or be caused by excessive licking)
- If your vet suspects that your cat may have T. foetus, they will recommend you bring in a fresh stool sample from your cat. They will then look at the sample under the microscope to see if they can find any of the tiny organisms or send it to a special veterinary lab where they can run a test called PCR to detect the organism.
- Most cases will resolve on their own but it’s a slow process, sometimes taking many months, and many owners (and cats!) may want to treat the disease to get rid of it faster.
- None of the drugs currently licensed in the UK for use in cats can kill T. foetus. However, there is an antibiotic called ronidazole that is used to treat the disease in the United States and this drug can be used in the UK if the cat’s owner provides their informed, written consent. Not all cats will respond to the drug and a few may develop side effects (neurological problems that go away once the drug is stopped), although the vast majority of cats won’t have any problems.