CONDITION
Tritrichomonas Foetus in Cats
Tritrichomonas foetus is a microscopic single-celled organism that can live in the large intestine of cats, most often causing persistent diarrhoea that may contain mucus or small amounts of blood. It spreads through direct contact with infected faeces, so it tends to be seen more commonly in young cats from multi-cat environments such as breeding catteries or shelters, though cats of any age living in any setting can be affected. Some cats carry the organism without showing signs at all. Owners typically notice loose or semi-formed stools that persist for weeks or months, sometimes improving briefly before returning. The cat often remains otherwise well — eating normally, maintaining weight, and behaving as usual — which can make the pattern puzzling. In some cases the diarrhoea resolves on its own over time, while in others it continues or recurs. This page explores what signs may appear, what is happening in the intestine when this organism is present, how it can be identified through testing, and what approaches exist for managing the condition. The goal is to help you understand the range of possibilities and what conversations may be useful as you and your vet work through the picture your cat is showing.
Why this matters now
Tritrichomonas foetus tends to be identified most often in young cats, typically under one year of age, particularly those coming from breeding catteries, rescue centres, or other multi-cat households where close contact and shared litter facilities increase the chance of transmission. Pedigree breeds, especially those kept in breeding programmes, appear in clinical reports more frequently, though this may reflect housing density rather than genetic susceptibility. Cats of any age can be affected, and those living alone can carry the organism if they were exposed earlier in life or during a period in a shelter or cattery.
The diarrhoea associated with this organism often begins within weeks to months of exposure, though the exact timing can be difficult to pinpoint because many cats show no signs at all during the early carrier phase. In cats that do develop diarrhoea, the pattern is typically one of persistence rather than sudden onset — loose stools may continue for weeks or months, sometimes with brief periods of improvement that give the impression of resolution before the signs return. Over time, some cats appear to clear the infection spontaneously and the diarrhoea stops, while in others the signs become chronic and continue for years, waxing and waning without a clear trigger.
Signals & patterns
Early signals
Loose or semi-formed stools
The stool may appear softer than usual, sometimes described as cow-pat consistency, or it may be partly formed with a loose portion. This change tends to persist rather than resolving after a day or two, which is often what prompts closer attention.
Mucus in the faeces
A clear, jelly-like coating or streaks of mucus may be visible on the surface of the stool. This reflects irritation or inflammation in the lining of the large intestine, where mucus is produced in response to disturbance.
Fresh blood on the stool surface
Small amounts of bright red blood may appear on the outside of the faeces or mixed into the softer portions. This typically indicates surface inflammation or minor damage to the lining of the colon rather than bleeding higher in the digestive tract.
Increased frequency of defaecation
The cat may visit the litter tray more often than usual, sometimes passing small amounts each time. This pattern can reflect urgency or discomfort associated with inflammation in the lower bowel.
Normal appetite and behaviour
Many cats continue to eat well, play normally, and maintain their weight despite the ongoing diarrhoea. This mismatch between gastrointestinal signs and overall demeanour can be puzzling and may delay investigation.
Later signals
Straining or discomfort during defaecation
The cat may spend longer in the litter tray, adopt a hunched posture, or vocalise during or after passing stool. This can reflect ongoing inflammation and sensitivity in the colon, making the act of defaecation uncomfortable.
Intermittent soiling outside the tray
Some cats begin to associate the litter tray with discomfort and may defaecate elsewhere, or they may not reach the tray in time if urgency increases. This is often a behavioural response to chronic intestinal irritation.
Weight loss or poor body condition
In cases where diarrhoea persists for many months without resolution, some cats begin to lose weight or develop a dull coat, though this is less common than in other causes of chronic diarrhoea. It may indicate secondary changes such as reduced nutrient absorption or concurrent illness.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
Last reviewed: Invalid Date ·