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Giardia in dogs

Written by Mara | December 18, 2025

Giardia is the most common gastrointestinal parasite in dogs. A Giardia infection is highly contagious and can also be transmitted from animals to humans. It is therefore important to recognise and treat a Giardia infection quickly. In addition, reinfection with Giardia is common, which makes it essential to take the right hygienic precautionary measures. In this article, we explain what Giardia is, how you can recognise it and what you can do about it for your dog.

What is Giardia?

Giardia is a single-celled gastrointestinal parasite that can cause diarrhoea and sometimes vomiting. It is the most common gastrointestinal parasite in dogs. In approximately 10 to 20% of dogs with diarrhoea, Giardia is the cause. Giardia does not only occur in dogs, but also in cats, rabbits, guinea pigs and other animals. It is also a zoonosis, which means that the disease can be transmitted from animals to humans. Young children and people with a weakened immune system are particularly at risk. If you maintain good hygiene as a healthy adult, the risk of infection is low.

A Giardia infection, also known as giardiasis, is highly contagious and therefore spreads quickly in places where multiple animals are kept together, such as kennels, catteries, shelters or dog walking services.

Is Giardia in dogs dangerous?

Infection with Giardia occurs via the mouth. The parasites eventually end up in the small intestine, where they attach themselves to the intestinal wall using a kind of suction disc. This damages the intestinal wall, which may be visible as blood in the stool. In the intestine, Giardia multiply rapidly. At the end of the intestine, the parasites form cysts. These cysts then leave the body via the faeces.

The cysts can survive for up to about a week in the faeces of an infected animal and for several weeks in soil or cold water. In a moist, cold environment, the cysts can even survive for several months. New infection occurs through contact with contaminated faeces, swimming in contaminated water, eating or drinking from a contaminated food or water bowl, contact with contaminated grass or for example when the coat containing cysts of an infected animal is licked.

Because Giardia mainly occurs in puppies, their faeces are often highly contagious. Giardia does not always cause symptoms. Many dogs carry the Giardia parasite without becoming ill. Animals with reduced resistance, such as puppies, sick animals and older animals, can become seriously ill. In those cases, a Giardia infection can be dangerous. A long-term infection with symptoms can also lead to chronic changes in the intestines. That is why it is important to detect and treat an infection as quickly as possible.

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Symptoms of Giardia in dogs

Especially in animals with a weakened immune system, the symptoms of a Giardia infection can be clearly visible. Healthy adult dogs can also be infected, but in this group the infection is not always noticeable, because they do not always show clear symptoms or they are carriers without symptoms but still shed the parasite.

The most common symptom of a Giardia infection is severe, recurring diarrhoea, which in some cases contains blood and or mucus. This is caused by damage to the intestinal wall. If an animal is infected with Giardia, this can worsen existing gastrointestinal conditions and stimulate the development of other complaints.

Giardia in puppies

Because puppies do not yet have a fully developed gastrointestinal tract and the gut microbiome is also not yet fully established, puppies can develop symptoms more quickly when infected with Giardia. Because their resistance is also not yet optimal, it is more difficult for a puppy to overcome the infection on its own. It is therefore important to start the right treatment and support quickly.

You should always be aware that it can take quite a long time, sometimes weeks to months, before the stool is completely normal again after a severe infection. If you want to treat or support your puppy with Giardia, always contact our veterinary team or your own vet first. Not all products and diets described here are suitable for use in puppies.

How do I know if my dog has Giardia?

If your dog suffers from long-term gastrointestinal complaints such as vomiting and diarrhoea, the advice is always to contact your vet. The vet will first perform a general examination, possibly followed by additional tests such as faecal examination. The faeces, preferably collected over several days, are assessed for smell, colour and consistency.

In addition, the vet will probably check for parasites and other possible causes of abnormal stools. The vet has several tests available to determine whether there is a Giardia infection, but a negative test does not always mean that there is no Giardia present. The cysts are shed intermittently, meaning not with every bowel movement. It may therefore be necessary to repeat the test after one week.

Giardia rapid test

In addition to testing at the vet, there are also rapid tests for Giardia that you can perform at home. The CVET Quick Test Giardia can help determine whether your dog is infected with the Giardia parasite. The Giardia antigen test quickly and reliably tests for the presence of Giardia antigen in your pet’s faeces.

If your pet tests positive for Giardia with the rapid test, this means that Giardia antigens have been detected in the faeces. It is then advisable to discuss a treatment plan with your vet.

Please note: these self-tests are not a replacement for veterinary advice. If your animal has loose stools, it is always advisable to contact your vet.

How is a dog with Giardia treated?

Treating Giardia is not always easy, as it can be a persistent infection. If there is a Giardia infection, the vet will treat the dog or cat with a deworming product based on fenbendazole, such as Panacur or No Worm Diacur, or with metronidazole. The latter is prescription-only and is only available via the treating vet.

Panacur for Giardia

Fenbendazole, also known as Panacur, is the first-choice treatment for Giardia. The dosage is 50 mg per kg for 3 to 10 days. It is well known that a treatment of 3 days is usually too short. In most cases, 5 days is used. Because there is a high risk of reinfection, it is also advised to repeat the treatment after 2 weeks.

If the symptoms do not improve sufficiently, Giardia should be tested again within 5 days after the last treatment. If the test is positive, it can be concluded that the Giardia has not yet been adequately controlled. If testing is done after 5 days, a positive result may also be due to reinfection.

Supplements for Giardia

You can also support your pet with supplements. This helps your dog build up more resistance against the parasite. It is often important to increase intestinal resistance with, for example, a probiotic such as Dr. Ann’s Probiotics. In addition, you can make the intestines less attractive to unwanted microorganisms with a product such as Puur Parasitus.

Dietary advice for Giardia

Parasitologists advise adjusting the diet in addition to treatment with medication. A low-fibre and easily digestible diet can help. The food should be low in carbohydrates and high in protein to prevent rapid growth of Giardia. A suitable diet is, for example, Vetality Gastrointestinal Dog Food.

How do you clean your home if your dog has Giardia?

In addition to treating all animals within a household, it is important to take certain hygienic measures when a Giardia infection has been diagnosed.

Disinfecting the environment

It is important to remove your dog’s faeces immediately during and after the treatment period, so that your animal and other animals do not come into contact with it. In addition, it is important to thoroughly clean the animal’s environment.

Smooth surfaces can be cleaned with quaternary ammonium compounds such as Oropharma Disinfect Spray or chlorine such as Halamid-D. Please note that these products require a contact time of at least 5 minutes to be effective. These products also only work in a clean environment, so you should first clean normally with water and soap before disinfecting.

For kennels, it is advised to allow surfaces to dry for at least 48 hours after treatment before introducing new animals. Carpets and fabric furniture, as well as baskets, blankets and toys, can be cleaned with steam or washed at a high temperature of at least 60 degrees Celsius. Do not forget food and water bowls and also the car.

Washing your animal

It is also important to wash your animal with shampoo, preferably on the last day of treatment. Use a shampoo with chlorhexidine, such as Dr. Ann’s Chlorhexidine Shampoo. Giardia cysts can still be present in the coat and can cause reinfection, for example through licking.

Especially in long-haired dogs, it can help to trim the hair around the anus short, so that this area can be kept clean more easily. In any case, wash the hind legs and rear end. Giardia is contagious to humans, so good personal hygiene is very important. Wash your hands thoroughly after touching your dog.

In addition, all animals in a household should be treated simultaneously when there is a Giardia infection, even if no symptoms are observed in the other animals.

Do you have any questions about Giardia or about deworming your dog in general? Please contact us via veterinarian@vetsend.co.uk.

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About the author

Mara van Brussel-Broere, Veterinarian at Vetsend

Graduated as a companion animal veterinarian from Utrecht University, she uses her practical experience to advise customers and share knowledge at Vetsend. She finds it important to provide pet owners with clear information about health and wellbeing.