Giardia in Dogs and Cats

Giardia is a microscopic intestinal parasite. Here is some information about how its spreads, the symptoms and how to reduce the risk.

Created: 2/8/2022 Updated: 8/3/2022 - Vicky Payne

cats, dogs, health, Health & Wellbeing, kitten, parasite, puppy

Occasional, self-limiting diarrhoea is common in dogs and cats, but ongoing or recurrent diarrhoea could be caused by a microscopic parasite called Giardia.

Giardia is a common intestinal parasite in dogs and (less commonly) cats, and infected pets may have no symptoms. Giardia can also infect people, and infections can pass between pets and people.

What is Giardia and how does it spread?

Giardia is a flagellated protozoan parasite: a microscopic, single-celled parasite that attacks the lining of the intestines.

In its trophozoite stage, Giardia attaches to the epithelial cells of the small intestine – absorbing nutrients and multiplying. The trophozoites migrate down the intestine and become encysted in the lower small, or large intestine. Three to ten days after infection, Giardia cysts are released into the environment in the faeces and are immediately infectious.

Giardia trophozoites are not infectious and can’t survive outside their host animal, but the cysts can survive for weeks or months in cool, damp conditions. Infected faeces can infect water, puddles, food sources, and the general environment. Pets catch Giardia by eating, drinking, or otherwise ingesting cysts from contaminated food, water, or objects.

Although Giardia is present in most environments, dogs living in close proximity to lots of other dogs (such as those in rehoming centres, multidog households, and boarding kennels) are at higher risk. Dogs and cats can shed Giardia without having any clinical symptoms. Pets under stress are more likely to develop Giardiasis, as are puppies and kittens.

Older dog being stroked by owner

Symptoms of Giardia in pets

Giardia can cause a range of symptoms in pets, and some animals can shed Giardia cysts without showing any symptoms. Common symptoms include:

  • Acute watery diarrhoea with a pungent smell

  • Chronic or repeated episodes of diarrhoea or soft faeces, often with a pungent smell and sometimes with blood

  • Foul smelling wind

  • Reduced appetite

  • Weight loss in older animals or poor weight gain in puppies and kittens

  • Vomiting (less common in pets than in people)

  • A bloated tummy in puppies and kittens

  • Reduced activity levels

These symptoms are seen with many tummy troubles and the severity varies between animals. You should seek veterinary advice if:

  • Your pet has had diarrhoea for more than 2-3 days

  • Your pet is a puppy, kitten or an elderly dog or cat

  • Your pet is on medication or has other health issues

  • Your pet has diarrhoea on and off for two weeks or more

  • Your pet is lethargic and unwilling to eat and drink

  • Your pet has repeated episodes of vomiting, especially if they can’t keep water down.

Diarrhoea can cause dehydration, especially in young and old pets. Dehydration can be particularly dangerous for puppies, kittens, and animals with other medical conditions such as kidney disease.

Symptoms of Giardia in humans

Giardiasis causes similar symptoms in people as it does in pets:

  • smelly diarrhoea

  • tummy pain or cramps

  • farting (flatulence)

  • burping that has an eggy smell

  • bloating

  • weight loss

Like pets, people can have giardiasis and spread it to others without having any symptoms. Humans can catch Giardia from contaminated food, water, objects, people, and pets. For more information see the NHS website

Worried ginger kitten hiding behind blanket

Preventing Giardia

As Giardia is commonly found in the environment it is impossible to prevent your pet coming into contact with infective cysts; however, there are steps you can take to reduce the risk.

  • Prevent your pet drinking from puddles, ponds, and other water from unknown sources

  • Take water with you on dog walks and wash and fill bowls at home every day

  • Pick up your dog’s poop when on a walk to reduce the risk of spreading giardia and infecting other pets

  • Kennels, dog walkers, home boarders, and dog breeders should use suitable cleaners which kill infectious organisms including Giardia. Bleach and household cleaners are often not effective!

  • Maintain good hygiene when cleaning up after your pet. Wash your hands or use a hand sanitiser if you are out on a dog walk

  • Cat litter trays should be cleaned and disinfected regularly

  • Minimise stress around rehoming and kennel stays

Giardia treatment for pets

When you visit your veterinary surgery, your vet will examine your pet and ask for details of their tummy troubles. Your vet may ask for a three-day ‘pooled’ faecal sample as this gives the best chance of detecting infectious causes of diarrhoea in dogs and cats. Your vet will supply a pot into which you put a small amount of faeces each day, for 3 days.

While waiting for results, your vet may advise an easily digestible food, electrolyte drinks to maintain hydration, and supportive probiotic treatment.

If Giardia is found in the faecal sample, and your pet still has symptoms, your vet will prescribe treatment. Treatment is aimed at preventing clinical symptoms but may not end the shedding of cysts. You should take your vet’s advice on cleaning your home and ensure everyone washes their hands after handling your pet or cleaning up after them.

Husky dog drinking water out of bottle outside

After treatment: returning to normal pet food

Pets who recover from Giardia can be left with a sensitive stomach for weeks or months. You may find that their normal diet triggers a return of diarrhoea. OSCAR’s nutritional experts can advise on easily digestible foods to support your cat or dog recovering from Giardia.

Giardia is a common infection in dogs and cats, especially those who have recently been rehomed or had a stay in kennels or with a home boarder. Infected pets may have digestive upsets ranging from acute watery diarrhoea to more chronic or intermittent signs, or they may have no symptoms at all. Good hygiene and cleaning practises reduce the risk of Giardia but seek veterinary advice if your pet has digestive symptoms that concern you.

Do you need further advice?

If you need any further advice, please contact the OSCAR Helpline Team on our freephone number 0800 195 8000 or email

©OSCAR Pet Foods Ltd