Tritrichomoniasis in Cats
Tritrichomoniasis is caused by a microscopic parasite, Tritrichomonas blagburni, that lives in the cat's large intestine. It produces colonic diarrhea that persists or recurs over weeks or even months, often foul-smelling, with mucus and so...
What is it?
Tritrichomoniasis is caused by a microscopic parasite, Tritrichomonas blagburni, that lives in the cat's large intestine.
It produces colonic diarrhea that persists or recurs over weeks or even months, often foul-smelling, with mucus and sometimes blood.
It mainly affects young cats, often from breeding facilities or catteries. Notably, these cats generally remain alert, playful, eat well, and do not lose weight, despite persistent diarrhea.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Chronic or recurrent diarrhea: soft to liquid stools, foul-smelling, often with mucus, sometimes with fresh blood.
Duration matters: a diarrhea lasting only a few days suggests another cause, whereas diarrhea present for more than three weeks, or that improves then returns in episodes, is suggestive of this condition.
Small involuntary fecal leakage: traces may be found where the cat sleeps or sits, without the cat having gone to the litter box.
Redness, swelling, and irritation around the anus, with the cat licking its rear persistently.
In more severe cases, part of the rectum protrudes through the anus.
Flatus in some cats.
The cat generally remains in good overall condition, with normal appetite and weight.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The parasite Tritrichomonas blagburni, which colonizes the lining of the large intestine.
It does not form eggs or resistant cysts: it survives only a short time outside the animal, which explains why it spreads mainly between cats living in close contact.
Young cats, most often under two years old.
Cats from catteries, breeding facilities, or shelters.
High density of cats with shared litter boxes.
Some studies suggest higher frequency in long-haired breeds, although this link has not been established with certainty.
Transmission
Infection occurs through direct contact with fresh feces from an infected cat, most often through a shared litter box or during mutual grooming.
Catteries, breeding facilities, and shelters, where many cats share the same litter boxes, are the most common places where transmission occurs.
Many cats remain carriers after the diarrhea resolves and can infect other cats.
Transmission to humans is not established.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian will ask about the diarrhea history: how long it has lasted, what relapses have occurred, and where the cat came from.
The parasite can be seen under a microscope in very fresh feces, but it is often missed; a negative result does not rule out the disease.
More sensitive tests, such as culture or DNA testing of the parasite in feces, are often needed to confirm the diagnosis.
Giardiasis is investigated at the same time, since the two parasites can coexist and look similar under the microscope.
The veterinarian will also rule out other causes of chronic diarrhea: inflammatory bowel disease, food intolerance.
Treatment
Treatment of tritrichomonosis is challenging. Only one antiparasitic has proven truly effective; it is used under veterinary supervision with monitoring, as it can cause nervous side effects.
Usual diarrhea treatments sometimes improve stool consistency temporarily, but the diarrhea returns when treatment stops: this is a clue that should raise suspicion for this disease.
Adapted nutrition, often high in fiber or highly digestible, helps improve stool consistency.
Without treatment, diarrhea often resolves on its own, but sometimes only after many months, and the cat may remain a carrier.
In a cattery, all cats are examined: treating only one animal risks recontamination.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Have any cat arriving from a breeding facility or shelter examined by a veterinarian if it has diarrhea.
Provide enough litter boxes, cleaned very regularly, and avoid overcrowding.
Isolate an affected cat from other cats while diagnosis and treatment are underway.
Before buying a kitten from a breeder, ask whether cases of chronic diarrhea have been documented in the cattery.
Possible complications
Lasting irritation and inflammation of the anal region.
Protrusion of part of the rectum through the anus, especially in young kittens that strain frequently.
Soiling caused by involuntary stool leakage, which can be difficult for the household to manage.
Prolonged carrier status and transmission to other cats.
When to see a veterinarian
Something red is coming out of your cat's anus: consult a veterinarian the same day.
In a male cat, straining in the litter box without producing anything may be a urinary blockage: seek emergency care.
Diarrhea has lasted more than three weeks, or returns after each treatment.
You find traces of stool where your cat sleeps.
The area around the anus is red, swollen, or your cat is licking the rear end constantly.
You see blood in the feces.
Prognosis
Tritrichomonosis is not typically a life-threatening disease in cats, but it is prolonged and distressing for both the animal and the household.
With accurate diagnosis and appropriate treatment, diarrhea resolves in many cats.
Relapse is possible and the cat may remain a carrier, which is why the check-ups recommended by your veterinarian are important.
Frequently asked questions
My young cat has had diarrhea for weeks but is otherwise in good health: tritrichomoniasis or inflammatory bowel disease?
A young cat from a breeding facility, which remains playful, eats well and does not lose weight, points more towards tritrichomonosis. Inflammatory bowel disease more often affects middle-aged to senior cats, with vomiting and weight loss. Only tests can determine the diagnosis.
Was the first stool examination negative; is the disease ruled out?
No. The parasite is difficult to see under the microscope. More sensitive tests are often necessary, using very fresh stool samples.
Why does diarrhea keep coming back after each treatment?
Because conventional diarrhea treatments do not eliminate this parasite: they sometimes improve stools for a time, then the diarrhea returns. These relapses are precisely an indicator of tritrichomoniasis.
Could my other cats catch it?
Yes, especially if they share the same litter boxes. Talk to your veterinarian about it: they can advise you to have the other cats examined and to review how the litter boxes are organized. Transmission to humans has not been established.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
Content reviewed by the TunisieVet editorial team · Updated 11 October 2026
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