Could Tritrichomonas Be Causing Your Cat’s Chronic Diarrhoea?

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 is an important cause of chronic large-bowel diarrhoea, especially in kittens, pedigree cats and cats from shelters, catteries or busy multi-cat homes. Affected cats often remain bright, playful and hungry despite producing persistently messy stools.

The mistake I see most often is repeatedly treating these cats for Giardia or giving course after course of metronidazole without obtaining the specific test needed to identify Tritrichomonas.

Quick Answer

Tritrichomonas blagburni, also still called feline Tritrichomonas foetus, is a microscopic protozoan that lives in the lower intestinal tract and causes chronic or intermittent colitis.

Typical signs include frequent foul-smelling stools, mucus, fresh blood, flatulence, straining and occasional faecal leakage in an otherwise bright young cat. Faecal PCR is the preferred diagnostic test. Ronidazole is the treatment of choice when treatment is appropriate, but it is unlicensed in cats, can cause neurological toxicity and should only be used after veterinary assessment. (ABCD cats and vets)

Tritrichomonas in Cats at a Glance

Question	Practical answer
What causes the infection?	A flagellated protozoan called Tritrichomonas blagburni
Which cats are most at risk?	Kittens, young cats, pedigree cats and cats living in groups
What does the diarrhoea look like?	Frequent, foul-smelling, soft or liquid stool with mucus, fresh blood and straining
Do cats usually seem ill?	Many remain bright, active and in reasonable body condition
How does it spread?	Cats ingest organisms from contaminated faeces, paws, coats and litter trays
Can a routine faecal float find it?	Usually not, because the organism has no conventional cyst stage
What is the preferred test?	PCR on fresh diarrhoeic faeces, ideally collected directly with a faecal loop
What is the preferred treatment?	Ronidazole, prescribed and compounded specifically for the individual cat
Can the infection resolve without treatment?	Yes, but diarrhoea may take months or up to two years to settle
Is it zoonotic?	The feline-adapted organism is not considered zoonotic

These points reflect current ABCD and Companion Animal Parasite Council guidance. (ABCD cats and vets)

What Is Tritrichomonas?

Tritrichomonas blagburni is a microscopic, highly motile, single-celled protozoan. It lives mainly on the mucosal surface of the distal small intestine, caecum and colon, where it contributes to intestinal inflammation and changes within the normal gut microbiome. (ABCD cats and vets)

Unlike Giardia, Tritrichomonas does not have a conventional resistant cyst stage. It is present mainly as a motile trophozoite with several flagella and an undulating membrane. The organism survives poorly once dry, although it can remain viable for several days in moist faeces. (ABCD cats and vets)

Is It Called Tritrichomonas blagburni or Tritrichomonas foetus?

Both names continue to appear.

The name Tritrichomonas blagburni was proposed for the feline-adapted organism previously called Tritrichomonas foetus. Current ABCD guidance uses T. blagburni, but the newer terminology is not universally accepted, so laboratories and articles may still report feline T. foetus. (ABCD cats and vets)

The feline strain is genetically and biologically distinct from the venereal Tritrichomonas strain affecting cattle. The feline-adapted organism is also distinct from Pentatrichomonas hominis, which can infect people and must occasionally be differentiated through PCR. (ABCD cats and vets)

Which Cats Are Most Likely To Be Affected?

Tritrichomonas infection is most commonly recognised in:

• Kittens and cats younger than one year

• Pedigree cats

• Breeding catteries

• Rescue groups and shelters

• Multi-cat households

• Cats attending shows or changing between group environments

• Cats sharing litter trays with infected housemates

Young cats are more likely to develop obvious clinical signs, but cats of any age can become infected. Some infected cats have completely normal stools and may still contribute to transmission. (ABCD cats and vets)

Crowding is a major practical risk because it increases shared litter use, faecal contamination and the likelihood that a cat will ingest organisms while grooming contaminated paws or fur. (ABCD cats and vets)

How Does Tritrichomonas Spread?

Transmission is primarily faecal to oral.

A cat passes live trophozoites in diarrhoeic faeces. Another cat then uses the same litter tray, contaminates its paws and swallows the organism while grooming. Direct faecal contamination of bedding, carriers or floors may also contribute. (ABCD cats and vets)

The organism does not remain viable indefinitely in the home. It survives best in fresh, moist faeces and is relatively easy to kill after physical cleaning and drying. This is why rapid removal of diarrhoea from litter trays is more valuable than spraying disinfectant around a tray that still contains organic material. (ABCD cats and vets)

There is no evidence that reproductive transmission plays an important role in cats, and the feline-adapted organism is not considered a human health risk. (ABCD cats and vets)

What Does Tritrichomonas Diarrhoea Look Like?

Tritrichomonas usually causes large-bowel diarrhoea, also called colitis.

Typical signs include:

• Frequent bowel movements

• Small quantities passed each time

• Soft, liquid or intermittently semi-formed stool

• Strong or offensive odour

• Mucus

• Fresh bright-red blood

• Straining

• Flatulence

• Urgency

• Faecal leakage or accidents

• Redness or swelling around the anus

The signs often wax and wane. A cat may produce almost normal stool for several days before the diarrhoea returns. (ABCD cats and vets)

Why Does the Cat Often Seem Otherwise Healthy?

Unlike many severe small-intestinal diseases, uncomplicated Tritrichomonas infection often does not cause substantial vomiting, dehydration or weight loss.

Many affected cats remain bright, active and hungry with reasonable body condition. That combination, a cheerful young cat paired with spectacularly offensive colitis, is one of the more characteristic clinical patterns. (ABCD cats and vets)

Less Typical Signs

Less commonly, affected cats may develop:

• Reduced appetite

• Vomiting

• Weight loss

• Failure to gain weight normally

• Abdominal discomfort

• Depression

• Dehydration

These signs increase concern for severe disease, a second intestinal infection or another gastrointestinal disorder occurring alongside the Tritrichomonas infection. (ABCD cats and vets)

How Worried Should You Be?

Lower Risk

Your cat has:

• Mild intermittent soft stool

• Normal appetite

• Normal energy

• No vomiting

• No weight loss

• No significant straining

• No dehydration

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

What to do: Monitor for several days. Arrange a veterinary assessment if the stool remains abnormal, repeatedly relapses or another cat in the household develops diarrhoea.

Moderate Concern

Your cat has:

• Diarrhoea lasting longer than one to two weeks

• Mucus or fresh blood

• Frequent small bowel movements

• Straining or urgency

• Strong-smelling stool

• Flatulence

• 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 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

• Marked lethargy

• Abdominal pain

• Dehydration

• Significant faecal incontinence

• Severe inflammation around the anus

What it may mean: More severe gastrointestinal 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

• Severe weakness

• Repeated vomiting

• Inability to eat or drink

• Profound dehydration

• Very pale gums

• Severe abdominal pain

• Wobbliness, tremors or seizures during ronidazole treatment

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

What to do: Attend an emergency veterinary hospital immediately.

What Else Can Cause Chronic Diarrhoea in a Young Cat?

A positive history does not confirm Tritrichomonas. Other causes of chronic or recurring diarrhoea include:

Possible condition	Important clues
Giardia	Soft or watery diarrhoea, possible weight loss and shared-environment exposure
Cryptosporidium	May occur alone or alongside Tritrichomonas
Cystoisospora and other parasites	More likely in kittens, rescues and poorly controlled group environments
Food-responsive enteropathy	Improvement during a properly controlled diet trial
Chronic inflammatory enteropathy	Persistent gastrointestinal disease after infectious causes are addressed
Dietary intolerance	Signs associated with a specific ingredient, diet change or overfeeding
Stress-associated colitis	Episodes linked to environmental disruption, but only after medical causes are excluded
Bacterial dysbiosis	May follow repeated antibiotics or repeated abrupt diet changes
Rectal or anal disease	Pain, swelling, discharge or difficulty passing stool
Intestinal neoplasia	More concerning in an older cat with weight loss or systemic illness

Co-infections with Giardia, Cryptosporidium and other pathogens are particularly important in multi-cat homes. One positive result does not prove that Tritrichomonas is the only contributor to the diarrhoea. (ABCD cats and vets)

When Is This an Emergency?

Tritrichomonas diarrhoea is rarely an emergency by itself, but young cats can deteriorate quickly if they stop eating or become dehydrated.

Seek urgent veterinary care if your cat develops:

• Complete food refusal

• Repeated vomiting

• Severe dehydration

• Marked weakness

• Collapse

• Significant abdominal pain

• Rapid weight loss

• Profuse or uncontrolled bleeding

• Minimal responsiveness

• Wobbliness, tremors or seizures during treatment

Stop ronidazole immediately and contact your veterinarian if neurological signs develop. Adverse effects may continue to progress for several days after the final dose, even though they are usually reversible with drug withdrawal and supportive treatment. (ABCD cats and vets)

What To Do Right Now

1. Record the Stool Pattern

Keep a daily log of:

• Stool frequency

• Consistency

• Mucus

• Fresh blood

• Straining

• Accidents

• Appetite

• Vomiting

• Body weight

• Medication

Photographs can be genuinely useful. A veterinary description of “chronic large-bowel diarrhoea” is easier to build when we can see whether the stool contains mucus, fresh blood or only poorly formed faeces.

2. Provide a Separate Litter Tray

Where practical:

• Separate the affected cat from unaffected cats

• Do not allow litter-tray sharing

• Scoop diarrhoea immediately

• Wash and dry trays regularly

• Use a dedicated scoop

• Keep food and water away from litter areas

Separation is especially important during treatment because reinfection from an untreated housemate can make an apparently appropriate course fail. (ABCD cats and vets)

3. Keep the Diet Consistent

Choose one complete and balanced diet the cat tolerates and keep it stable while the diagnosis is being established.

Repeatedly switching between high-fibre food, bland diets, raw food, probiotics and several medications can worsen dysbiosis and make it impossible to know which change helped. Current ABCD guidance specifically cautions that frequent dietary and treatment changes may prolong diarrhoea. (ABCD cats and vets)

4. Maintain Hydration and Food Intake

Ensure the cat continues eating and drinking.

A kitten, diabetic cat, obese cat or medically fragile cat that stops eating deserves earlier intervention. Fluids, anti-nausea treatment, pain relief or assisted nutrition may be needed when another illness is present.

5. Arrange the Correct Test

Tell your veterinarian:

• How long the diarrhoea has been present

• Whether there is mucus or fresh blood

• How many cats share the home

• Whether another cat has diarrhoea

• Which parasite tests have already been performed

• Whether metronidazole or another antibiotic was recently given

• Whether the cat came from a cattery, shelter or rescue

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

6. Do Not Start Ronidazole “Just in Case”

Ronidazole has a narrow safety margin and no feline licence. Its potential to cause neurological toxicity makes empirical treatment difficult to justify when appropriate testing is available. (ABCD cats and vets)

How Is Tritrichomonas Diagnosed?

PCR Testing

Faecal PCR is the preferred diagnostic method.

PCR is more sensitive than wet-mount microscopy or culture and can differentiate Tritrichomonas from Giardia and Pentatrichomonas hominis. Results are generally available within several days through a reference laboratory. (ABCD cats and vets)

PCR has limitations:

• No test is 100% sensitive

• Shedding may be intermittent

• Faecal inhibitors may cause false-negative results

• PCR detects DNA from living and dead organisms

• Some infected cats have no clinical signs

• A positive result may not explain every gastrointestinal sign

The result must therefore be interpreted alongside the cat’s stool pattern, age, household exposure and other diagnostic findings. (ABCD cats and vets)

What Is the Best Sample?

The preferred sample is:

• Fresh

• Diarrhoeic or mucoid

• Collected directly from the rectum using a faecal loop

• Free from cat litter

• Submitted according to the laboratory’s instructions

A study involving samples from 1,717 cats found that faecal-loop collection was more likely to produce a positive PCR result than colonic flushing. Freshly voided stool may still be accepted, but a directly collected sample provides the best opportunity to obtain mucus containing adherent organisms. (PubMed)

Recent antibacterial treatment may reduce diagnostic yield. Where it is medically safe, current ABCD guidance recommends withdrawing oral antibacterial treatment for around seven days before sample collection. Do not stop prescribed medication without first discussing it with the treating veterinarian. (ABCD cats and vets)

Direct Faecal Wet Mount

A wet mount allows a veterinarian to look for live, motile trophozoites under a microscope.

Tritrichomonas typically moves rapidly with a jerky, erratic forward motion. Giardia trophozoites tend to move more slowly in a falling-leaf pattern. (ABCD cats and vets)

The sample must be:

• Very fresh

• Preferably collected directly from the rectum

• Kept at room temperature

• Examined immediately, or at least within six hours

• Not refrigerated, because refrigeration kills the trophozoites

The major limitation is extremely poor sensitivity. Reported sensitivity may be as low as 2% and no higher than approximately 15% in some reviews. A negative wet mount cannot rule out infection. (ABCD cats and vets)

InPouch Culture

A very small amount of fresh diarrhoeic faeces can be placed in a specialist culture pouch.

Culture confirms that living organisms are present and is more sensitive than a direct wet mount, but less sensitive than PCR. A positive result may take up to seven days, while the pouch generally requires 12 days of incubation before it can be considered negative. (ABCD cats and vets)

Too much faeces may allow bacterial overgrowth, so the sample added to the pouch should be only around the size of a grain of rice. (ABCD cats and vets)

Why Can a Routine Faecal Float Be Negative?

Tritrichomonas does not form the hardy conventional cyst or egg stage detected by standard flotation methods.

A cat can therefore have repeated negative faecal floats while remaining PCR-positive for Tritrichomonas. Routine flotation remains useful for identifying other intestinal parasites but does not exclude this infection. (Companion Animal Parasite Council)

Is a Colonic Biopsy Needed?

Usually not.

Trophozoites can occasionally be seen in colonic biopsies, but histopathology has poor sensitivity and requires invasive sampling. Biopsy is generally reserved for cats already undergoing investigation for inflammatory bowel disease, cancer or another chronic intestinal condition. (ABCD cats and vets)

Does Every Positive Cat Need Treatment?

Not necessarily.

Some infected cats have no diarrhoea. Others have mild signs that can be managed while the infection is allowed to resolve naturally. Ronidazole also carries a genuine toxicity risk and does not clear every infection. (ABCD cats and vets)

In practice, treatment becomes more compelling when:

• Diarrhoea is persistent or severe

• The cat is repeatedly straining

• Faecal leakage is affecting hygiene or welfare

• The perianal skin is inflamed

• The household contains several vulnerable cats

• The infection is difficult to control through separation

• The cat is being rehomed or entering another multi-cat environment

• The owner can administer medication accurately and monitor for toxicity

Watchful management may be reasonable when signs are mild, the cat remains healthy, treatment risks outweigh likely benefits or the cat is too young, pregnant or nursing. This decision should be made with the attending veterinarian.

How Is Tritrichomonas Treated?

Ronidazole

Ronidazole is the current treatment of choice.

The generally recommended veterinary protocol is:

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

This use is unlicensed or off-label in cats. Informed owner consent, accurate current body weight and appropriate veterinary compounding are important. (ABCD cats and vets)

Why Accurate Weight Matters

Ronidazole’s recommended dosage is close to the upper limit considered safely tolerated in cats.

A dosing error that appears small can matter in a kitten or lightweight cat. The cat should be weighed accurately rather than having the dose estimated from a previous visit or rounded from an owner’s bathroom scale. (ABCD cats and vets)

Which Cats Should Not Receive Ronidazole?

Current ABCD guidance advises against ronidazole in:

• Kittens aged 12 weeks or younger

• Pregnant queens

• Nursing queens

• Cats that previously developed neurological toxicity from ronidazole

The drug is teratogenic and should not be administered during pregnancy or lactation. (ABCD cats and vets)

Why Is It Usually Given as a Capsule?

Ronidazole is extremely bitter.

It is generally compounded into intact gelatin capsules rather than liquids or pastes. A bitter liquid may cause severe salivation, food aversion and difficulty ensuring the full dose is swallowed. (ABCD cats and vets)

Caregivers should:

• Wear disposable gloves

• Avoid opening or crushing the capsule

• Avoid touching or inhaling loose powder

• Wash hands after administration

• Keep medication away from children and other animals

• Follow the compounding pharmacy’s storage instructions

What Side Effects Should You Watch For?

Ronidazole toxicity may cause:

• Lethargy

• Reduced appetite

• Wobbliness

• Poor coordination

• Tremors

• Seizures

• Other unusual neurological behaviour

Caregivers can check coordination each day through gentle play or by watching the cat walk and jump normally. (ABCD cats and vets)

Stop treatment immediately and contact the veterinarian if any neurological sign develops.

Do not restart ronidazole after suspected neurotoxicity. Signs may continue worsening for several days after the medication is stopped, but they are usually reversible with withdrawal and appropriate supportive care. (ABCD cats and vets)

How Quickly Should the Diarrhoea Improve?

Some cats improve during the treatment course. Others take several weeks for stool quality to normalise because colonic inflammation and intestinal dysbiosis can continue after parasite numbers fall.

Soft stool on the final treatment day does not automatically prove treatment failure. (ABCD cats and vets)

Does Ronidazole Always Clear the Infection?

No.

Approximately 20% to 25% of treated cats may remain infected, relapse or fail to respond fully. Ronidazole-resistant isolates have also been reported. (PubMed)

Possible reasons include:

• Incorrect dose

• Inaccurate body weight

• Missed doses

• Poor compounding

• Reinfection from another cat

• Drug resistance

• A concurrent parasite or intestinal disease

• Persistent dysbiosis after infection

Do Metronidazole or Other Treatments Work?

Metronidazole

Metronidazole is not considered a reliable treatment for feline Tritrichomonas.

It may temporarily change stool consistency or alter the intestinal microbiome, but it has little or no consistent ability to clear the infection. Repeated metronidazole courses can delay the correct diagnosis and contribute to ongoing dysbiosis. (ABCD cats and vets)

Tinidazole

Tinidazole has some activity against Tritrichomonas and may be considered when ronidazole is unavailable.

However, it is also unlicensed in cats and appears less effective. Evidence is limited, and eradication has not been consistently demonstrated. (ABCD cats and vets)

Other Medications

Auranofin showed promising laboratory activity but failed to treat naturally infected cats effectively in a clinical study. There is currently no approved feline treatment that provides a proven, safer equivalent to ronidazole. (ABCD cats and vets)

Do High-Fibre Diets or Probiotics Help?

There is no proven universal Tritrichomonas diet.

Some cats may produce better stools on a carefully selected fibre-adjusted or highly digestible food, but responses vary. High fibre should not be presented as a cure, and home remedies including pumpkin, yoghurt, turkey and rice have not consistently controlled the diarrhoea. (Companion Animal Parasite Council)

Early evidence suggests that selected Enterococcus faecium probiotics may reduce relapse when used with ronidazole, but they have not clearly shortened the time to clinical improvement. Better controlled studies are still required. (ABCD cats and vets)

The most practical nutritional advice is:

• Choose one complete and balanced diet

• Keep the diet consistent

• Avoid frequent food changes

• Do not introduce several supplements together

• Maintain adequate calorie and water intake

• Use probiotics only as a veterinary-directed adjunct

Repeated diet and supplement trials may destabilise the microbiome and prolong the diarrhoea. (ABCD cats and vets)

Should a Cat Be Tested Again After Treatment?

The draft recommendation to PCR test every cat at one to two weeks and again at 20 weeks is not the current standard approach.

Current ABCD guidance recommends retesting by PCR when diarrhoea persists or returns more than two weeks after completing the 14-day ronidazole course. Routine testing at a fixed 20-week point is not specifically recommended. (ABCD cats and vets)

If the PCR Is Positive

Review:

• Whether every dose was given

• Whether the dose matched an accurate body weight

• Whether the medication was compounded properly

• Whether untreated cats shared litter trays

• Whether reinfection was possible

• Whether drug resistance may be present

Do not automatically repeat ronidazole, particularly if the cat previously showed neurological abnormalities. (ABCD cats and vets)

If the PCR Is Negative but Diarrhoea Continues

Consider:

• Giardia

• Cryptosporidium

• Other parasites

• Food-responsive enteropathy

• Chronic inflammatory enteropathy

• Residual colonic inflammation

• Intestinal dysbiosis

• Another gastrointestinal diagnosis

PCR detects DNA from both viable and non-viable organisms, while no diagnostic test has perfect sensitivity. Results must always be interpreted with the cat’s clinical response. (ABCD cats and vets)

How Should a Multi-Cat Household Be Managed?

Ideally, every cat’s infection status would be determined through PCR, with infected cats separated from uninfected cats.

That is not always financially or logistically realistic. PCR can also miss some infected cats because shedding is intermittent. (ABCD cats and vets)

A practical plan may include:

• Testing every cat with diarrhoea

• Providing individual litter trays

• Separating treated cats from untreated cats

• Treating untested cats with diarrhoea when directed

• Testing asymptomatic housemates when reinfection is a concern

• Considering treatment of all contacts only in difficult, persistent household outbreaks

• Cleaning faecal contamination immediately

• Reducing crowding and stress

Cats without clinical signs can still be infected. The decision to expose an asymptomatic cat to ronidazole should therefore balance transmission risk against medication toxicity. (ABCD cats and vets)

Litter-Tray Hygiene

Use:

• At least one tray per cat, plus an additional tray where possible

• Frequent faeces removal

• Dedicated litter scoops

• Regular washing with detergent

• Thorough drying before reuse

• Separate trays for cats undergoing treatment

The organism is fragile once removed from moist faeces, so prompt physical cleaning and drying are central to control. (ABCD cats and vets)

Can Tritrichomonas Resolve Without Treatment?

Yes.

An estimated 88% of infected cats eventually return to normal stool without specific treatment. The median reported duration is approximately nine months, with a range from five months to two years. Resolution tends to take longer in larger multi-cat households. (PubMed Central (PMC))

Clinical improvement does not always equal complete parasite clearance. Around half of cats may remain PCR-positive after the diarrhoea has resolved, and some may relapse following stress or a major diet change. (ABCD cats and vets)

Monitoring without ronidazole may be reasonable when:

• Signs are mild

• Appetite and growth are normal

• The household can manage hygiene

• The kitten is too young for ronidazole

• The cat is pregnant or nursing

• Previous toxicity has occurred

• Medication risk outweighs the effect of the diarrhoea

The disadvantage is that the cat may continue producing abnormal stool and transmitting infection for many months.

What Is the Prognosis?

The overall prognosis is generally good.

Most affected cats remain systemically well, and stool quality eventually improves through treatment or spontaneous resolution. The greatest challenges are often household hygiene, repeated unsuccessful treatment trials, drug toxicity, reinfection and the frustration of managing chronic faecal accidents. (ABCD cats and vets)

The prognosis should be reconsidered when a cat has:

• Significant weight loss

• Failure to grow

• Persistent vomiting

• Severe abdominal pain

• Marked lethargy

• Repeated dehydration

• Poor response despite a negative follow-up PCR

These findings are less typical of uncomplicated Tritrichomonas infection and justify a broader investigation.

Common Tritrichomonas Mistakes

Assuming It Must Be Giardia

The two organisms can produce similar signs and may be confused on microscopy. They can also infect the same cat.

Relying on a Routine Faecal Float

A normal flotation result does not exclude Tritrichomonas.

Sending a Dry, Litter-Contaminated Sample

A fresh mucoid sample collected directly with a faecal loop provides better diagnostic sensitivity.

Repeatedly Prescribing Metronidazole

Metronidazole is not a reliable curative treatment and may further disrupt the intestinal microbiome.

Starting Ronidazole Without Confirmation

The medication has a narrow safety margin and should not be used casually.

Estimating the Cat’s Weight

A small dosing error may significantly increase toxicity risk.

Continuing Treatment After Wobbliness Develops

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

Expecting Perfect Stool on Day 14

Residual inflammation can persist for several weeks after treatment.

Automatically Repeating Ronidazole

Persistent diarrhoea may be caused by another parasite, residual dysbiosis or a noninfectious intestinal disease.

Changing the Diet Every Few Days

Constant dietary experiments may prolong dysbiosis and make the case harder to interpret.

How Can Tritrichomonas Be Prevented?

There is no vaccine and no standard preventive dewormer that reliably prevents feline Tritrichomonas.

Practical prevention includes:

• Reducing overcrowding

• Quarantining newly acquired cats with diarrhoea

• Testing chronic diarrhoea before introducing a cat into a colony

• Providing enough litter trays

• Removing faeces promptly

• Preventing litter-tray sharing during treatment

• Cleaning carriers and equipment between cats

• Keeping food and water separate from toileting areas

• Investigating diarrhoea before breeding, showing or rehoming a cat

• Avoiding unnecessary antibiotic and dietary trials

The most effective preventive principle is simple: prevent fresh contaminated faeces from reaching another cat’s mouth.

Frequently Asked Questions

Is Tritrichomonas contagious to people?

No. The feline-adapted organism is not considered zoonotic. Normal handwashing and hygienic disposal of diarrhoeic faeces are still sensible. (ABCD cats and vets)

Will metronidazole cure Tritrichomonas?

Usually not. Metronidazole may temporarily change stool quality but has little or no reliable efficacy for clearing the infection. (ABCD cats and vets)

Does every infected cat need ronidazole?

No. Some mildly affected cats can be monitored because diarrhoea frequently resolves naturally. Treatment decisions should consider severity, household transmission, the cat’s age and the medication’s toxicity risk.

When should PCR be repeated after treatment?

Retesting is recommended when diarrhoea persists or recurs more than two weeks after completing treatment. A routine repeat test at 20 weeks is not required for every clinically recovered cat. (ABCD cats and vets)

Can a cat become infected again after treatment?

Yes. Reinfection can occur when the treated cat continues sharing litter trays or close space with an untreated infected cat.

Final Thoughts

Tritrichomonas should be considered whenever a young cat has persistent, foul-smelling large-bowel diarrhoea but remains otherwise bright and active.

The most important points are:

1. Tritrichomonas commonly causes chronic colitis in kittens and young cats.

2. Mucus, fresh blood, straining and foul odour are typical.

3. Cats may remain infected without obvious clinical signs.

4. A standard faecal float does not rule it out.

5. PCR on a fresh rectal-loop sample is the preferred test.

6. A negative wet mount cannot exclude infection.

7. Ronidazole is the treatment of choice but is unlicensed and potentially neurotoxic.

8. Accurate dosing and daily neurological monitoring are essential.

9. Metronidazole is not a reliable cure.

10. High-fibre diets and probiotics have not been proven to eliminate the infection.

11. Reinfection is a major concern in multi-cat households.

12. Retesting is most appropriate when diarrhoea persists or returns after treatment.

13. Untreated diarrhoea usually resolves eventually, but this may take up to two years.

14. Persistent illness, weight loss or vomiting should trigger investigation for another condition.

The mistake that causes the greatest harm is repeatedly treating the diarrhoea without identifying what is actually causing it. Once Tritrichomonas is properly confirmed, the choices around treatment, monitoring and household control 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.