Last updated: 26 September 2026
Giardia is a single-celled intestinal parasite that can cause recurring, soft, pale and very foul-smelling diarrhoea in cats. It mostly affects kittens under one year old, shelter and cattery populations, and multi-cat households. Adult cats often carry it without symptoms. It can be detected at home from a fresh stool sample with an antigen rapid test. Treatment is prescribed by a vet, and cleaning and bathing are at least as important as the medication, because a cat can reinfect itself from its own coat.
In this article we explain how cats catch Giardia, which symptoms to watch for, how you can test at home, how it is treated, and what you can do to stop the infection coming back. Giardia in dogs is covered in a separate article: Giardia in dogs.
What is Giardia and how do cats catch it?
Giardia duodenalis lives in the small intestine. Hardy, microscopic cysts are shed in the faeces, and just a few are enough to cause infection. According to the ABCD (European Advisory Board on Cat Diseases) guideline, in favourable, damp conditions the cysts can remain infectious in the environment for months.
Cats can become infected:
- from contaminated litter or a shared litter tray;
- from contaminated water, food bowls or surfaces;
- while grooming, from their own coat or a companion's coat where cysts have stuck;
- when a new, infected cat joins the household.
In cats it takes 5–16 days from infection until cysts are shed, and shedding is intermittent: on some days hardly any cysts end up in the stool. That is why a single negative sample does not always rule out infection.
Which cats are most at risk?
According to the ABCD guideline, infection rates are 1–20% in the general cat population, but can reach 30–40% in shelters and catteries. Infection is most common in cats under one year old. In an international survey, 31% of samples from catteries were positive.
- Kittens: they have the most cases with symptoms, and in them diarrhoea leads to weight loss soonest.
- Shelter, rescued and newly adopted cats: many animals live together in a small space, and stress is common.
- Breeders and multi-cat households: because of shared litter and grooming, the infection quickly goes round.
If a new cat arrives, keep an eye on its stool in the first few weeks. More on this: Adopting a cat: what you need to know about screening tests.
What symptoms does Giardia cause in cats?
The most common symptom is small-intestinal diarrhoea. The stool is typically described as:
- soft or mushy, sometimes watery;
- pale in colour, greasy-looking;
- much smellier than usual;
- fluctuating: fine for days, then loose again.
It can be accompanied by weight loss, poor growth in kittens, wind, and dirty, sticky fur under the tail. Fever, severe lethargy and bloody diarrhoea are not typical of Giardia. If you see these, especially in a kitten, a different, more urgent cause must be considered.
| Possible cause | Typical picture | How urgent? |
|---|---|---|
| Giardia | Recurring, soft, pale, foul-smelling stool; the cat usually still eats and plays | Not an emergency, but it needs treatment. Worth testing. |
| Cat parvo (panleukopenia) | Sudden onset, vomiting, often bloody diarrhoea, fever, severe lethargy, especially in unvaccinated kittens | Urgent – see a vet immediately. |
| Food change, stress | Loose stool for a day or two after moving house, new food or travel | Keep an eye on it. If it does not settle within 1–2 days, take the next step. |
| Intestinal worms | Diarrhoea, pot belly, sometimes visible worms in the stool | Discuss deworming with your vet. |
How is Giardia detected in cats?
According to ABCD, detecting Giardia antigen in faeces has the same sensitivity and specificity as microscopic (flotation) examination at the clinic, but is much simpler. Because of intermittent shedding, flotation requires 3 samples taken on different days. PCR is the most sensitive, but it is a lab test and more expensive.
At home, you can do it with the MancsLab Giardia Ag rapid test like this:
- Sampling: take a sample from fresh faeces with the swab provided. Wear gloves.
- Mixing: put the swab into the buffer vial, mix thoroughly and close it.
- Applying: put 3 drops of sample into the well marked S on the cassette.
- Reading: read after 5–10 minutes. After 15 minutes the result can no longer be interpreted.
According to the manufacturer's validation against PCR, the test has a sensitivity of 98.57% and a specificity of 99.13%. Two lines (C and T) mean a positive result, even if the T line is faint. If only the C line is visible, the result is negative. If there are symptoms, it is worth repeating with a new sample after 2–3 days.
Important: according to CAPC (Companion Animal Parasite Council) recommendations, the antigen test is best used in cats with symptoms. ABCD does not recommend routine treatment of positive cats without symptoms either. In multi-cat households, always discuss next steps with your vet.
How is Giardia treated in cats?
Treatment is a job for the vet. According to international recommendations, fenbendazole or metronidazole is usually prescribed, typically for 5–7 days, sometimes both together. The dose is determined by the vet based on the cat's body weight. Metronidazole requires caution in pregnant, nursing or epileptic cats. Never give your cat human medication or leftover antibiotics on your own initiative.
Medication on its own is often not enough. If cysts remain in the environment and on the coat, the cat can become reinfected after the course. That is why cleaning and bathing are needed too.
Cleaning and bathing: how to stop it coming back
- Litter tray: empty it completely every day, and during treatment scald it with hot water or wash it with disinfectant.
- Disinfection: according to ABCD, products containing quaternary ammonium compounds are effective against the cysts. The literature also describes hot water and chlorine as effective.
- Drying: cysts like moisture. After disinfecting, let surfaces dry thoroughly.
- Textiles: wash beds and blankets at the highest possible temperature.
- Bathing: to remove cysts stuck to the coat, washing the area under the tail with shampoo is recommended at the start and end of treatment. Ask your vet how to do this, as most cats do not like baths.
- Handwashing: always wash your hands after cleaning the litter tray and handling the cat.
Is a follow-up test needed after treatment?
This is a common question, and the answer is not a straightforward yes. Giardia antigen can remain detectable for a while in the stool even after successful treatment, so an antigen test done straight after the course can be misleading. If symptoms have resolved by the end of treatment, international recommendations say routine follow-up testing is not needed. If the diarrhoea does not go away or comes back, the vet will typically use a microscopic stool examination to check whether it is treatment failure or reinfection.
A home test helps most when new symptoms appear, a new cat arrives, or several animals in a cattery or shelter have loose stools.
Can people catch Giardia from cats?
Giardia in cats is mostly a type adapted to cats. According to ABCD, genotype A, which can also infect humans, has been found in some infected cats in Europe (35–95% depending on the study). However, direct cat-to-human transmission has not been proven so far; the main sources of human infection are contaminated water and vegetables. The risk can be kept low with thorough handwashing, regular litter cleaning and supervising children. If someone in the family has persistent diarrhoea, mention to the doctor that a Giardia-positive animal lives in the home.
Multi-cat households, catteries and shelters
Where several cats live together, Giardia rarely stays with one animal. If one cat is positive, discuss with your vet whether the others should be tested too, and which ones need treatment. For breeders and shelters, the 5-pack is more convenient and better value. More tips: Multi-pet households: how to stop infections spreading.
Frequently asked questions about Giardia in cats
What does the stool of a cat with Giardia look like?
Typically soft or mushy, pale, greasy-looking and much smellier than usual. The diarrhoea often fluctuates: the stool is fine for days, then becomes loose again.
Can Giardia go away on its own in cats?
Symptoms may improve temporarily, but the cat can keep shedding cysts and reinfect itself or its companions. With persistent or recurring diarrhoea, ask your vet for treatment.
How long does Giardia treatment take in cats?
The course of medication typically lasts 5–7 days. Cleaning, disinfecting and keeping the coat clean should be done throughout treatment, and especially at the end.
Can I test my cat for Giardia at home?
Yes, with an antigen rapid test on a fresh stool sample, in 5–10 minutes. If positive, see a vet. If negative but symptoms persist, repeat after 2–3 days, because shedding is intermittent.
Does a positive cat without symptoms need treatment?
According to the ABCD guideline, routine treatment of Giardia-positive cats without symptoms is not recommended. In multi-cat households and catteries, the vet decides what to do.
Is Giardia from cats dangerous to people?
The risk is low and can be reduced further with good hygiene. Direct cat-to-human transmission has not been proven so far, but handwashing after cleaning the litter tray is always important.
Summary
If your cat's stool has been fine one day and loose, pale and very smelly the next for weeks, think of Giardia, especially in a kitten, a shelter cat or a multi-cat home. A home rapid test gives you an answer in minutes. If it is positive, your vet will prescribe treatment, and thorough cleaning and keeping the coat clean will prevent reinfection.
Giardia Ag rapid test for cats and dogs →
From a fresh stool sample, result in 5–10 minutes. Also available in a 5-pack for multi-cat households and catteries.
Sources
- ABCD – European Advisory Board on Cat Diseases: Guideline for Giardiasis. abcdcatsvets.org
- Feline Giardia: Transmission, Diagnosis, and Treatment. Today's Veterinary Practice. todaysveterinarypractice.com
- Cornell University College of Veterinary Medicine: Giardia – infection, treatment and prevention. vet.cornell.edu
- MancsLab Giardia Ag instructions for use (with manufacturer's validation data)
Important: this article provides general information and does not replace veterinary advice. Medication must always be prescribed by a vet. MancsLab rapid tests are intended for preliminary screening at home.