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Tritrichomonas: The Diarrhoea That Will Not Quit
The young pedigree cat parasite every breeder should know by name.
Last reviewed
The young pedigree cat parasite every breeder should know by name.
Last reviewed
Tritrichomonas foetus is a single celled parasite of the large intestine with a very particular victim profile: young cats, usually under two, and disproportionately pedigree cats from multi cat backgrounds. It is one of those names general cat owners rarely hear and responsible breeders never stop hearing.
It spreads through shared litter trays in close contact households, and its calling card is stamina: diarrhoea that runs for weeks or months, improving and relapsing, long after everything else has been treated.
The signature is chronic large bowel diarrhoea: soft to liquid stools, often foul smelling, sometimes with mucus or flecks of blood, passed frequently and with urgency, occasionally with a sore or inflamed rear end from the traffic. The cat is usually bright, eating and maintaining weight, which is exactly what makes it so confusing.
The pattern to recognise: a young cat whose diarrhoea keeps returning after every treatment seems to work. Standard stool tests often miss it; diagnosis usually needs a specific PCR test your vet sends away, and asking for it by name is entirely reasonable.
Treatment is a specific prescription medicine given precisely as directed, because this parasite shrugs at ordinary wormers and standard antibiotics. Some cases also self resolve over many months as immunity matures, so your vet may discuss both routes.
Household management does the rest: strict tray hygiene, one tray per cat plus a spare, and daily disinfection while any cat is affected. In breeding households this is a screen and manage disease, which is why our own routine includes testing rather than hoping.
Unlike giardia and coccidia, tritrichomonas has no tough cyst stage at all: it exists only as a delicate swimming organism that dies quickly in dry conditions, cold, and ordinary environments. It survives by never really leaving home, passing between cats through very fresh stool contact, which in practice means shared litter trays in close company.
That fragility is genuinely useful news: separate trays, prompt scooping and dry clean surfaces attack the parasite at its weakest point, and a fastidious cat living alone essentially cannot keep the infection circulating. The whole disease is an artefact of communal living.
Tritrichomonas dies in refrigerated samples and does not float in the standard flotation test, so the routine parasite screen can come back clean forever while the organism thrives. Finding it needs a fresh warm sample examined immediately under the microscope, a special culture pouch, or best of all the PCR test that detects its DNA.
This is one of the few conditions where owners genuinely help by naming the suspect: a young pedigree cat, months of relapsing smelly diarrhoea, every routine test clear, is the textbook picture, and asking your vet directly about tritrichomonas PCR is not backseat driving, it is pattern recognition.
Here is the honest expectation setting: even untreated, most infected cats eventually clear tritrichomonas on their own as immunity matures, but eventually can mean many months and occasionally a couple of years, with flare ups during stress along the way. Treated cats usually improve much faster, though some relapse before clearing fully.
Meanwhile the cat is typically bright, growing and happy, which makes the disease more exhausting for the human than the patient. The management rhythm is patience plus hygiene plus a vet relationship that expects the marathon, not the sprint.
A tritrichomonas diagnosis in one cat raises the household question immediately: the parasite spreads through shared trays via the faecal route, and housemates may already carry it silently. Your vet will map who gets tested and whether the group treats together.
Meanwhile the practical regime is tray discipline: enough trays for separation, scooped promptly, washed with scalding water on schedule, and the infected cat’s tray zone kept apart where the house allows. The organism dies quickly in dry environments, so hygiene here is genuinely effective.
The strange mercy of tritrichomonas is systemic mildness: affected cats typically stay bright, keep appetite and hold weight even while the large bowel runs chaos. The suffering concentrates at the rear, sore skin under the tail, dignity lost, carpets casualties.
That profile sets the urgency fairly: it is rarely an emergency, always a welfare project, and any case that breaks the pattern, weight loss, lethargy, blood in quantity, vomiting, has either a complication or a different diagnosis, and goes back for reassessment promptly.
Because the parasite travels through multi cat environments, a buying household is entitled to plain answers: has the litter or its home had persistent diarrhoea investigated, what testing was done, and what the outcomes were. Vague answers about sensitive stomachs deserve follow up questions.
Our position is simple: gut health here is monitored litter by litter, investigated properly when anything persists, and documented. A seller who discusses stool quality without embarrassment is telling you how the nursery actually runs; squeamish marketing is its own answer.
Cats that clear tritrichomonas, by treatment or by the slow self resolution route, generally go on to entirely normal lives: the colon recovers, stools normalise, and long term damage is not the pattern. A minority remain carriers for a period after symptoms cease, which is why vets sometimes retest.
The after care is ordinary excellence: good diet, stress kept low since flare ups track upheaval in some recovered cats, and any relapse of the signature smell and softness reported early with the history attached. One properly diagnosed episode equips an owner to spot any sequel in days.
Tritrichomonas foetus is the specialist behind stubborn, smelly large bowel diarrhoea in young cats that shrugs off every ordinary treatment. It is a fragile organism needing specific tests, sometimes repeated, and treatment is a single specific prescription medicine given exactly to plan. Multi cat households manage it together because it passes between sharers, weight and welfare usually hold up while the bowel misbehaves, and untreated cases often self resolve over months to years. Kittens newly home should read coccidia and giardia first.
Different single celled parasites with overlapping symptoms, distinguished by specific testing, and the distinction matters because treatments differ completely. Chronic diarrhoea that failed giardia treatment is a classic tritrichomonas clue.
The feline strain is not a practical human risk in ordinary households, and dogs have their own related organisms. Standard tray hygiene covers the theoretical edges.
Because this organism dies fast in ordinary stool samples and hides from routine floats: it needs fresh material into specific tests. The diagnostic route is genuinely different, which is half the reason cases go unnamed for months elsewhere.
The specific treatment is effective and respected, with neurological side effects rare and monitored for, which is why it is prescription only and exactly dosed. It is also why guessing with random wormers wastes precious months.
Typically months, sometimes a couple of years, of intermittent smelly episodes before the immune system finally wins. It is a legitimate path your vet may discuss for mild cases; treatment mostly buys speed and carpets.
True reinfection needs a source, another shedding cat, so recurrence questions usually point at the household map rather than the medicine. Single cat homes that clear it generally stay clear.
Almost never: managed trays, testing and treatment handle the household version. Rehoming decisions on parasite grounds alone would be drastic surgery for a treatable logistics problem.
If the pattern sounds familiar but the cat is a kitten in a new home, read coccidia first, and giardia completes the stubborn diarrhoea trilogy.
Beyond our library, ESCCAP covers this in owner friendly depth, and International Cat Care adds the clinical detail. See the culprit itself: the Tritrichomonas foetus page shows the organism in motion under the microscope.