Tritrichomonas in Cats: Symptoms, Testing and Ronidazole Treatment

By Dr Duncan Houston

A young cat with months of foul-smelling diarrhoea, mucus, fresh blood and repeated straining may have more than a sensitive stomach.

Tritrichomonas infection is an important cause of chronic large-bowel diarrhoea, particularly in kittens, pedigree cats and cats living in crowded multi-cat environments. Affected cats often remain bright, playful and hungry despite producing persistently abnormal stools.

The condition is frustrating, but the prognosis is usually good. The priorities are confirming the diagnosis accurately, avoiding ineffective treatment trials, using ronidazole safely when indicated and preventing reinfection from other cats.

Quick Answer

Tritrichomonas is a flagellated protozoan parasite that causes chronic or intermittent large-bowel diarrhoea in cats. Typical signs include frequent foul-smelling stools, mucus, fresh red blood, flatulence, straining and occasional faecal incontinence.

Faecal PCR is the preferred diagnostic test. Ronidazole is the treatment of choice for clinically affected cats, but it is unlicensed, has a narrow safety margin and can cause neurological toxicity. Treatment should therefore follow a confirmed diagnosis and direct veterinary supervision. (ABCD cats and vets)

Tritrichomonas at a Glance

Question	Practical answer
What organism causes it?	Usually Tritrichomonas blagburni, historically called feline Tritrichomonas foetus
Which cats are most affected?	Kittens, cats under one year and cats from multi-cat homes, shelters or breeding catteries
What type of diarrhoea occurs?	Frequent small amounts of foul-smelling stool with mucus, fresh blood and straining
Do cats usually seem sick?	Many remain bright, active and maintain their weight
How is it transmitted?	Faecal to oral transmission, often through shared litter trays and contaminated paws
What is the best test?	PCR on a diarrhoeic faecal sample, ideally collected directly from the rectum
What is the main treatment?	Ronidazole at a veterinarian-prescribed dose for 14 days
Can treatment fail?	Yes. Approximately one in five to one in four cats may remain infected or relapse
Can it resolve without treatment?	Yes, but spontaneous improvement may take several months to two years
Can humans catch it?	The feline-adapted organism is not considered zoonotic

These points reflect current ABCD and CAPC guidance. (ABCD cats and vets)

What Is Tritrichomonas Infection?

Tritrichomonas blagburni is a microscopic, single-celled flagellated protozoan that lives mainly within the mucus covering the ileum, caecum and colon.

It adheres to the intestinal lining, contributes to inflammation and disrupts the normal intestinal microbiome. The result is usually colitis, which produces frequent, urgent and poorly formed stools rather than the large-volume weight-losing diarrhoea more typical of severe small-intestinal disease. (ABCD cats and vets)

The organism exists mainly as a motile trophozoite. It does not produce the hardy environmental cyst stage seen with parasites such as Giardia. This makes it relatively fragile outside the cat, although it can remain viable for several days in moist faeces. (Companion Animal Parasite Council)

Is It Tritrichomonas blagburni or Tritrichomonas foetus?

Both names may still appear on laboratory reports, veterinary articles and medication information.

The name Tritrichomonas blagburni was proposed for the feline-adapted organism previously called Tritrichomonas foetus. Current ABCD guidance uses T. blagburni, but the terminology is not yet universal.

Feline isolates are genetically and biologically distinct from the reproductive strains associated with cattle. Throughout this article, “Tritrichomonas” refers to the feline intestinal organism. (ABCD cats and vets)

Which Cats Are Most at Risk?

Tritrichomonas can affect any cat, but infection is particularly associated with:

• Cats younger than one year

• Pedigree cats

• Breeding catteries

• Shelters and rescue facilities

• Multi-cat households

• Cats attending shows

• Environments with shared litter trays

• Cats with concurrent intestinal parasites

Crowding matters because close contact increases faecal contamination, shared litter use and grooming of contaminated paws. Young cats are also more likely to develop obvious diarrhoea than older infected cats. (ABCD cats and vets)

Some cats remain completely asymptomatic despite shedding the organism. This means a cat without diarrhoea may still contribute to transmission within a household. (ABCD cats and vets)

How Is Tritrichomonas Transmitted?

Transmission occurs through the faecal to oral route.

A typical sequence is:

1. An infected cat passes trophozoites in diarrhoeic faeces.

2. Another cat uses the contaminated litter tray.

3. Organisms contaminate the paws or coat.

4. The second cat swallows them while grooming.

Shedding may begin approximately two to seven days after infection and may persist for months. There is no evidence that reproductive tract transmission plays an important role in cats. (ABCD cats and vets)

Because the organism survives best in moist faeces, prompt litter removal is more important than attempting to sterilise every square centimetre of the house.

What Does Tritrichomonas Diarrhoea Look Like?

Tritrichomonas usually causes signs of large-bowel diarrhoea or colitis.

Typical features include:

• Frequent bowel movements

• Small quantities passed each time

• Liquid to semi-formed stool

• Strong or foul odour

• Mucus

• Fresh red blood

• Straining

• Urgency

• Flatulence

• Stool leakage or faecal incontinence

• Redness or swelling around the anus

The diarrhoea may improve temporarily and then return. Cats commonly remain bright, playful and in reasonable body condition despite the duration and smell of the stools. (ABCD cats and vets)

Less Typical Signs

Some affected cats may also develop:

• Reduced appetite

• Failure to gain weight

• Weight loss

• Vomiting

• Abdominal discomfort

• Depression

• Dehydration

These signs are less typical of uncomplicated feline tritrichomonosis. When they are prominent, veterinarians become more concerned about severe disease, concurrent infection or a separate intestinal condition. (ABCD cats and vets)

How Worried Should You Be?

Lower Immediate Risk

Your cat has:

• Intermittent soft stool

• Normal appetite

• Normal energy

• No vomiting

• No weight loss

• No dehydration

• No significant straining

What it may mean: Mild colitis or an early intestinal infection is possible.

What to do: Arrange a non-emergency veterinary examination if the stool does not return to normal within several days or repeatedly becomes abnormal.

Moderate Concern

Your cat has:

• Diarrhoea lasting more than one to two weeks

• Mucus or fresh blood

• Frequent small bowel movements

• Straining

• Flatulence

• Foul-smelling stool

• A history of cattery, shelter or multi-cat exposure

What it may mean: Tritrichomonas, Giardia, Cryptosporidium or another chronic colitis disorder becomes more likely.

What to do: Arrange veterinary testing within the next few days. Ask specifically whether Tritrichomonas PCR is appropriate.

High Concern

Your cat has:

• Reduced appetite

• Vomiting

• Weight loss

• Failure to grow normally

• Abdominal pain

• Marked lethargy

• Dehydration

• Frequent stool leakage

• Significant perianal inflammation

What it may mean: More severe intestinal disease or a concurrent disorder may be present.

What to do: Seek same-day veterinary assessment, particularly for a kitten.

Critical

Your cat has:

• Collapse

• Profound weakness

• Severe dehydration

• Repeated vomiting

• Inability to eat or drink

• Very pale gums

• Severe abdominal pain

• Tremors, wobbliness or seizures during ronidazole treatment

What it may mean: A serious complication, concurrent disease or medication toxicity may be present.

What to do: Attend an emergency veterinary hospital immediately.

This is a practical triage framework based on the usual mild systemic presentation of Tritrichomonas and the less common severe signs described in current guidance. (ABCD cats and vets)

When Is This an Emergency?

Tritrichomonas diarrhoea itself is rarely immediately life-threatening, but kittens can deteriorate more quickly than healthy adult cats.

Seek urgent veterinary care when your cat develops:

• Complete food refusal

• Repeated vomiting

• Marked dehydration

• Severe weakness

• Collapse

• Significant abdominal pain

• Rapid weight loss

• Uncontrolled or profuse bleeding

• Minimal responsiveness

• Neurological signs during ronidazole treatment

Stop ronidazole immediately and contact your veterinarian if your cat becomes lethargic, loses their appetite, walks abnormally, trembles or has a seizure. Neurological toxicity may continue to worsen for several days after the medication is stopped, even though it is usually reversible with withdrawal and supportive care. (ABCD cats and vets)

What Else Can Cause Similar Diarrhoea?

Tritrichomonas is an important differential diagnosis, but it is not the only cause of chronic diarrhoea in a young cat.

Possible condition	Useful clues
Giardia	Soft to watery diarrhoea, possible weight loss, sometimes identified by antigen testing or flotation
Cryptosporidium	May occur alongside Tritrichomonas, especially in multi-cat environments
Other intestinal parasites	Risk increases with inadequate parasite control or outdoor exposure
Food-responsive enteropathy	Signs may improve with a properly controlled dietary trial
Chronic inflammatory enteropathy	Persistent disease despite treatment of infectious causes
Bacterial enteropathy	Interpretation requires care because some bacteria are also found in healthy cats
Stress-associated colitis	Often linked to environmental disruption but remains a diagnosis of exclusion
Anal or rectal disease	Pain, swelling, discharge or difficulty passing stool

Co-infection with Giardia, Cryptosporidium and other enteropathogens is well recognised and can make the signs more severe or prevent an apparently correct treatment from succeeding. (ABCD cats and vets)

A positive PCR result should also be interpreted alongside the clinical pattern. Detection of an organism does not always prove that it is the only cause of the diarrhoea. (Sage Journals)

What To Do Right Now

1. Record the Stool Pattern

Keep a simple daily record of:

• Stool frequency

• Consistency

• Mucus

• Fresh blood

• Straining

• Accidents outside the tray

• Appetite

• Vomiting

• Body weight

• Medication

Photographs of the stool can help demonstrate the large-bowel pattern.

2. Give the Cat a Separate Litter Tray

Where practical:

• Separate the affected cat from uninfected cats

• Do not allow litter-tray sharing

• Scoop faeces promptly

• Empty and wash trays frequently

• Keep the tray and surrounding area dry

• Use dedicated scoops and cleaning equipment

This reduces faecal exposure and the risk of reinfection. (Companion Animal Parasite Council)

3. Keep the Cat Eating and Hydrated

Offer a consistent, complete and balanced diet that the cat tolerates.

Avoid repeatedly changing between:

• High-fibre diets

• Low-fibre diets

• Raw diets

• Homemade diets

• Multiple probiotics

• Repeated courses of antimicrobials

Frequent diet and treatment changes may perpetuate dysbiosis and prolong diarrhoea rather than allowing the intestinal microbiome to stabilise. (ABCD cats and vets)

4. Arrange Proper Faecal Testing

Tell your veterinarian about:

• The duration of diarrhoea

• Multi-cat exposure

• Previous Giardia testing

• Previous metronidazole or antibiotics

• Whether litter contamination is possible

• Whether another cat has diarrhoea

Ask whether a rectal-loop sample for Tritrichomonas PCR is available.

5. Avoid Empirical Ronidazole

Ronidazole should not be given “just in case”.

Its narrow safety margin, lack of feline licensing and potential neurotoxicity make confirmation of infection particularly important before treatment whenever clinically possible. (ABCD cats and vets)

How Is Tritrichomonas Diagnosed?

PCR Testing

Faecal PCR is the preferred diagnostic method.

Advantages include:

• High sensitivity

• High specificity

• Ability to distinguish Tritrichomonas from Giardia and Pentatrichomonas hominis

• Rapid laboratory turnaround

• No need to observe living organisms

Limitations include:

• Intermittent shedding can produce false-negative results

• Faecal inhibitors may interfere with testing

• PCR detects DNA from both living and dead organisms

• Poor sample collection may reduce sensitivity

A positive PCR confirms that Tritrichomonas DNA is present, but it does not always prove that viable organisms remain after recent treatment. (ABCD cats and vets)

What Is the Best Sample?

The highest-yield sample is generally:

• Fresh

• Diarrhoeic or mucoid

• Free from cat litter

• Collected directly from the rectum using a faecal loop

Rectal-loop collection appears more sensitive than colonic flushing, while freshly voided litter-box faeces are the least preferred sample.

Oral antibacterial treatment may reduce the chance of detecting the organism. Where medically safe, the laboratory or veterinarian may recommend withholding antibacterial medication for approximately seven days before sample collection. Do not stop prescribed medication without veterinary direction. (ABCD cats and vets)

Direct Faecal Wet Mount

A small amount of fresh diarrhoeic faeces is mixed with saline and examined under a microscope.

Tritrichomonas moves with a rapid, jerky, erratic forward motion. Giardia trophozoites move more slowly in a characteristic falling-leaf pattern.

The advantages are speed and low cost. The major disadvantage is low sensitivity. The sample should ideally be examined immediately and no later than approximately six hours after collection. Refrigeration kills the motile trophozoites and makes the test unsuitable. (ABCD cats and vets)

InPouch Culture

A tiny amount of fresh diarrhoeic faeces is placed into a specialised culture pouch.

• A positive result may be visible within seven days.

• A culture cannot be called negative until no organisms have been found by approximately 12 days.

• Culture confirms viable organisms.

• Sensitivity is better than a direct smear but lower than PCR.

The amount of faeces matters. Overloading the pouch may allow bacterial overgrowth and make interpretation more difficult. (Companion Animal Parasite Council)

Why Routine Faecal Flotation May Be Negative

Tritrichomonas has no conventional resistant cyst stage.

Routine flotation is therefore not an adequate test for ruling out feline tritrichomonosis. A cat can have repeated negative flotation tests while remaining PCR-positive. (Companion Animal Parasite Council)

How Is Tritrichomonas Treated?

Ronidazole

Ronidazole is currently considered the treatment of choice.

The commonly recommended veterinary protocol is:

Ronidazole 30 mg/kg by mouth once daily for 14 days.

This is an off-label or unlicensed use in cats and should be prescribed and compounded specifically for the individual patient. Accurate current body weight is essential because overdosing increases the risk of neurotoxicity. (ABCD cats and vets)

Which Cats Should Not Receive Ronidazole?

Current ABCD guidance advises that ronidazole should not be used in:

• Kittens aged 12 weeks or younger

• Pregnant queens

• Nursing queens

• Cats that previously developed neurological toxicity from the drug

The drug is teratogenic and should be handled carefully by people administering it. (ABCD cats and vets)

How Should Ronidazole Be Handled?

Ronidazole is extremely bitter and is generally compounded into intact capsules rather than a paste or liquid.

Caregivers should:

• Wear disposable gloves

• Give only the prescribed capsule

• Avoid opening, splitting or crushing it

• Avoid inhaling or touching loose powder

• Wash hands after administration

• Keep it securely away from children and other animals

• Follow the compounding pharmacy’s storage instructions

If a capsule breaks or leaks, contact the veterinary clinic or pharmacy for disposal advice rather than attempting to estimate and administer the remaining powder. (ABCD cats and vets)

What Side Effects Can Ronidazole Cause?

Potential adverse effects include:

• Lethargy

• Reduced appetite

• Wobbliness or ataxia

• Tremors

• Seizures

• Other abnormal neurological behaviour

Approximately 5% of treated cats developed anorexia or neurological abnormalities in one study, although risk appears higher with inaccurate or excessive dosing.

Treatment must be stopped immediately if adverse signs appear. It should not be restarted after neurological toxicity. (ABCD cats and vets)

How Quickly Should the Diarrhoea Improve?

Some cats improve during treatment, but stool quality may take several weeks to normalise.

A lack of perfectly formed stool on the final treatment day does not automatically mean ronidazole has failed. Residual colonic inflammation and microbiome disruption may continue after parasite numbers have fallen. (ABCD cats and vets)

Does Ronidazole Always Work?

No.

Current guidance estimates that approximately 20% to 25% of treated cats may remain infected, fail to respond fully or relapse.

Possible reasons include:

• Incorrect dose

• Inaccurate body weight

• Missed capsules

• Poor-quality or incorrectly compounded medication

• Reinfection from another cat

• Ronidazole-resistant organisms

• A concurrent enteric infection

• A separate noninfectious intestinal disorder

Treatment failure should be confirmed through appropriate PCR testing rather than assumed solely because the stool remains abnormal. (ABCD cats and vets)

Do Metronidazole or Other Drugs Work?

Metronidazole

Metronidazole is not considered a reliable treatment for feline Tritrichomonas infection.

It may temporarily alter stool consistency or the intestinal microbiota, but clearance of infection is uncommon. Repeated empirical courses can delay the correct diagnosis and contribute to ongoing dysbiosis. (ABCD cats and vets)

Tinidazole

Tinidazole may be considered when ronidazole is unavailable.

The reported alternative protocol is 30 mg/kg orally once daily for 14 days, but available evidence suggests that it is less effective and may reduce shedding without reliably eliminating infection. It is also unlicensed in cats. (ABCD cats and vets)

Auranofin and Experimental Treatments

Auranofin showed promising activity in laboratory testing but was ineffective in cats with naturally occurring infection.

This is a useful reminder that killing an organism in a test tube does not automatically mean a drug will reach effective concentrations within the feline colon. (ABCD cats and vets)

Do Diet Changes and Probiotics Help?

There is no proven “Tritrichomonas diet”.

Some cats may have better stool quality on a carefully selected, highly digestible or fibre-adjusted diet, but dietary response varies.

Evidence for probiotics remains limited. Preliminary data suggest that one commercial Enterococcus faecium probiotic used alongside ronidazole may reduce relapse risk, but it did not make cats improve faster, and stronger controlled studies are still needed. (ABCD cats and vets)

The practical approach is usually:

• Choose one complete, balanced diet

• Measure the amount consistently

• Avoid abrupt or repeated changes

• Treat dehydration, nausea and pain when present

• Add a veterinarian-selected probiotic only as an adjunct

• Do not expect a supplement to clear the parasite

How Should Multi-Cat Households Be Managed?

Household control can be more challenging than treating one cat.

Ideally, Identify Infection Status

Where resources allow, the veterinarian may recommend PCR testing all cats and separating:

• Infected from uninfected cats

• Cats with diarrhoea from cats with normal stool

• Treated cats from untreated cats

This approach is imperfect because PCR can occasionally produce false-negative results and clinically normal cats can remain infected. (ABCD cats and vets)

When Testing Every Cat Is Not Practical

A more realistic household plan may include:

• Testing every cat with diarrhoea

• Separating untreated diarrhoeic cats from treated cats

• Providing individual litter trays

• Scooping faeces immediately

• Treating asymptomatic contacts only when specifically advised

• Reassessing the plan if reinfection or repeated treatment failure occurs

In difficult cattery or household outbreaks, veterinarians may consider treating all in-contact cats, including asymptomatic cats, after weighing the cost, risk of neurotoxicity and likelihood of ongoing transmission. (ABCD cats and vets)

Cleaning the Environment

Tritrichomonas is relatively fragile outside the cat.

Useful measures include:

• Frequent removal of faeces

• Washing litter trays before organic material dries

• Using a suitable household disinfectant after cleaning

• Drying trays thoroughly

• Cleaning contaminated floors and carriers

• Washing soiled bedding

• Preventing stool contamination of food and water areas

• Reducing crowding

The organism survives best in moist faeces and does not persist like a hardy parasite cyst, so prompt physical cleaning is highly effective. (ABCD cats and vets)

Should Cats Be Retested After Treatment?

Routine immediate testing of every clinically improved cat is not always straightforward because PCR may detect DNA from nonviable organisms and asymptomatic infection may be difficult to exclude completely.

Current ABCD guidance recommends retesting when diarrhoea persists or returns more than two weeks after completing the 14-day ronidazole course. (ABCD cats and vets)

If the PCR Is Positive

The veterinarian should review:

• Whether the capsule was given every day

• Whether the dose matched an accurate body weight

• Whether the medication was compounded correctly

• Whether another cat remained untreated

• Whether litter trays were shared

• Whether reinfection occurred

• Whether ronidazole resistance is possible

Do not automatically repeat ronidazole without this review, particularly if the cat previously showed adverse effects.

If the PCR Is Negative but Diarrhoea Continues

Persistent diarrhoea does not necessarily mean the original treatment failed.

Further investigation may include:

• Giardia

• Cryptosporidium

• Other parasites

• Food-responsive disease

• Chronic inflammatory enteropathy

• Residual dysbiosis

• Another cause of colitis

A negative PCR should shift the investigation towards other infectious and noninfectious causes rather than triggering repeated empirical ronidazole courses. (ABCD cats and vets)

Can Tritrichomonas Resolve Without Treatment?

Yes.

Untreated diarrhoea often eventually improves, with one study reporting a median duration of approximately nine months and a range of five months to two years.

Larger multi-cat households tended to have longer-lasting disease. Approximately 88% of affected cats ultimately returned to normal faecal consistency. (ABCD cats and vets)

Clinical resolution does not always mean complete elimination of the organism. Some cats remain PCR-positive after their stools improve and may develop another episode following stress or a major dietary change. (ABCD cats and vets)

When Might Monitoring Without Ronidazole Be Reasonable?

A veterinarian may discuss supportive management rather than immediate ronidazole when:

• The cat is mildly affected

• Appetite and growth are normal

• The household can manage hygiene effectively

• The cat is younger than 12 weeks

• The cat is pregnant or nursing

• Previous ronidazole toxicity has occurred

• The risks of treatment outweigh the severity of signs

The downside is that diarrhoea and infectious shedding may continue for many months.

What Is the Prognosis?

The overall prognosis is usually good.

Most cats maintain good general health, and stool quality eventually improves either following treatment or spontaneous resolution. The major challenges are:

• The duration of diarrhoea

• Household contamination

• Reinfection

• Medication toxicity

• Persistent dysbiosis

• Co-infections

• Frustration from repeated ineffective treatment trials

Cats with poor growth, significant weight loss, persistent vomiting or severe systemic illness deserve a wider diagnostic investigation because uncomplicated Tritrichomonas infection usually leaves cats relatively bright and well. (ABCD cats and vets)

Common Tritrichomonas Mistakes

Assuming Every Chronic Diarrhoea Case Is Giardia

Giardia and Tritrichomonas can look similar microscopically and can infect the same cat.

PCR or appropriate species-specific testing is needed when the distinction matters.

Relying on Routine Faecal Flotation

Tritrichomonas does not have the conventional cyst stage detected by standard flotation.

Sending a Dry Litter-Contaminated Sample

A fresh mucoid rectal-loop sample substantially improves the chance of a useful result.

Treating With Metronidazole Repeatedly

Metronidazole is not a reliable curative treatment for Tritrichomonas.

Starting Ronidazole Without Confirming Infection

The drug’s narrow safety margin makes guesswork difficult to justify.

Using an Inaccurate Body Weight

Even a small dosing error matters in a kitten or small cat.

Continuing Ronidazole After Wobbliness Begins

Ataxia, tremors, reduced appetite or seizures require immediate discontinuation and veterinary contact.

Changing the Diet Every Few Days

Repeated changes may worsen dysbiosis and make it impossible to judge whether treatment is working.

Assuming Persistent Diarrhoea Means the Parasite Remains

A negative post-treatment PCR should prompt investigation for other causes.

How Can Tritrichomonas Be Prevented?

There is no vaccine and no routine preventive dewormer that reliably eliminates the risk.

Practical prevention includes:

• Reducing overcrowding

• Quarantining newly acquired cats with diarrhoea

• Testing cats before introducing them into breeding colonies

• Providing adequate litter trays

• Scooping faeces promptly

• Avoiding communal litter trays where infection is known

• Cleaning carriers and equipment between cats

• Reducing stress and abrupt dietary changes

• Investigating chronic diarrhoea before breeding, showing or rehoming a cat

• Keeping treated cats separate from untreated infected cats

The most effective control measure is preventing fresh faecal contamination from reaching another cat’s mouth. (ABCD cats and vets)

Frequently Asked Questions

Is Tritrichomonas contagious to people?

The feline-adapted organism is not considered zoonotic.

Normal hygiene is still important. Wear gloves when cleaning diarrhoeic faeces, wash your hands thoroughly and take extra precautions when someone in the household is immunocompromised. (ABCD cats and vets)

Will metronidazole cure Tritrichomonas?

Usually not.

Metronidazole has little or no reliable efficacy for clearing feline Tritrichomonas infection. Ronidazole remains the preferred treatment when therapy is indicated. (ABCD cats and vets)

Should every cat in the house be treated?

Not automatically.

Testing, clinical signs, the number of cats, ability to separate them and history of reinfection all influence the decision. Treating all contacts may be considered in difficult multi-cat outbreaks, but ronidazole exposure should not be taken lightly. (ABCD cats and vets)

Can my cat recover without ronidazole?

Yes.

Most untreated cats eventually develop normal stools, but improvement may take many months and sometimes up to two years. Some remain infected after the diarrhoea resolves. (ABCD cats and vets)

Why does my cat still have diarrhoea after a negative PCR?

Possible explanations include residual colonic inflammation, dysbiosis, Giardia, Cryptosporidium, food-responsive disease or another form of chronic enteropathy.

A negative PCR makes persistent Tritrichomonas infection less likely but does not explain every chronic diarrhoea case. (ABCD cats and vets)

Final Thoughts

Tritrichomonas is one of the most important infectious causes of chronic large-bowel diarrhoea in young cats.

The most important points are:

1. The feline organism is commonly called Tritrichomonas blagburni, although T. foetus remains widely used.

2. Infection is most common in young cats and crowded multi-cat environments.

3. Typical stools are frequent, foul-smelling and contain mucus or fresh blood.

4. Many affected cats remain bright and maintain their weight.

5. Transmission occurs through ingestion of contaminated faeces.

6. The organism has no hardy conventional cyst stage.

7. PCR on an appropriate faecal sample is the preferred diagnostic test.

8. A rectal-loop sample is more reliable than litter-box faeces.

9. Wet mounts are quick but frequently miss infection.

10. Ronidazole is the preferred treatment but is unlicensed and potentially neurotoxic.

11. Accurate body weight and compounding are critical.

12. Ronidazole should not be used in kittens aged 12 weeks or younger or in pregnant or nursing queens.

13. Neurological signs require immediate discontinuation.

14. Approximately 20% to 25% of cases may fail treatment or relapse.

15. Persistent diarrhoea after treatment does not automatically prove persistent infection.

16. Multi-cat hygiene and separation are essential for preventing reinfection.

17. Untreated signs usually resolve eventually, but this may take up to two years.

18. The prognosis is generally good.

The mistake that causes the most harm is repeatedly treating the stool without confirming what is living in it. Once Tritrichomonas is correctly identified, the treatment and household-control decisions become much clearer.

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ASK A VET™ can help you organise stool photographs, PCR results, household exposure, treatment timing and possible ronidazole side effects while you work directly with your veterinarian. A kitten that becomes dehydrated, stops eating, repeatedly vomits or develops wobbliness, tremors or seizures still requires immediate hands-on veterinary care.