Giardia in Dogs
Giardia is a microscopic intestinal parasite that can cause diarrhoea in dogs.
What is Giardia?
Giardia is a single-celled protozoal parasite. It is not a worm, bacterium or virus. Infection with Giardia is known as giardiasis or giardiosis.
The parasite has an active form that lives in the intestines and a protective cyst form that is passed in faeces. These cysts are immediately infectious and can survive for long periods in cool, damp environments.
How dogs become infected
Dogs become infected when they swallow Giardia cysts. This may happen through:
- Drinking contaminated water
- Licking or eating contaminated soil
- Eating food contaminated with infected faeces
- Licking contaminated paws, coats or hindquarters
- Contact with contaminated bowls, bedding, toys or crates
- Contact with infected dogs or contaminated environments
Only a small number of cysts may be needed to cause infection. Reinfection is common if cysts remain on the dog’s coat or in its surroundings.
Possible symptoms
- Sudden, persistent or intermittent diarrhoea
- Soft or watery stools
- Foul-smelling stools
- Mucus in the faeces
- Greasy-looking stools
- Abdominal discomfort or excess wind
- Reduced appetite
- Weight loss
- Lethargy in more severe cases
- Occasional vomiting
Blood is not a typical feature of Giardia and may suggest another or an additional problem. Contact your vet if blood is present in your dog’s stools.
Diagnosis
Your vet will usually test a faecal sample. Giardia cysts may not be present in every stool, so more than one sample or a different type of laboratory test may be required.
A positive result should be considered alongside the dog’s symptoms because healthy dogs without diarrhoea can sometimes test positive.
Current veterinary guidance generally does not recommend treating a healthy dog with no clinical signs solely because it has tested positive. An exception may be part of an infection-control programme in a kennel or breeding establishment. Your vet will advise you according to the individual circumstances.
Treatment
Treatment is normally recommended for a dog that tests positive and has symptoms. Your veterinary surgeon will select the appropriate prescribed treatment and length of course.
Fenbendazole is commonly used as a first treatment. Metronidazole may be considered in some cases, including infections that have not responded as expected.
Do not use leftover worming products or antibiotics without veterinary advice. The correct medicine, strength and duration must be chosen for the individual dog.
A dog with severe diarrhoea or dehydration may require additional treatment. Your vet may also recommend a temporary, highly digestible diet to support the digestive system.
If symptoms continue after treatment, further testing may be needed to check for persistent infection, reinfection or another cause of diarrhoea.
Cleaning and preventing reinfection
- Remove faeces immediately from the garden and on walks. Seal it in a bag and dispose of it safely.
- Wash your hands thoroughly after handling your dog, its faeces, food, bowls or bedding.
- Clean food and water bowls every day and provide fresh drinking water.
- Clean toys, crates and hard floors regularly while your dog is being treated.
- Wash bedding at 60°C or above where the material allows, and dry it thoroughly.
- Steam-clean suitable surfaces or use a disinfectant recommended by your vet, following its instructions.
- Bathe the dog, particularly the hindquarters, paws and tail area, at the end of treatment to remove faecal material and cysts from the coat.
- Do not allow the dog to drink from puddles, ponds, streams or communal water bowls.
- Remove standing water from containers in the garden.
- Keep an affected dog away from dog parks, shared exercise areas and communal water until your vet says it is safe to return.
- Tell your vet if there are other dogs or cats in the household.
Grass and soil are extremely difficult to disinfect. Do not apply bleach or other household disinfectants to the garden. Prompt removal of faeces, reducing standing water and allowing areas to dry are safer ways to reduce environmental contamination.
Diet and probiotics
There is no single diet or probiotic suitable for every dog with Giardia. Dietary requirements will depend on the severity of the diarrhoea, the dog’s age, general health and normal food.
Your vet may recommend an easily digested gastrointestinal diet during recovery. Probiotics may be suggested for some dogs, but they do not replace prescribed treatment or environmental hygiene.
Avoid making sudden or extreme changes to the diet unless advised by your veterinary surgeon.
Can people catch Giardia from dogs?
Humans can develop giardiasis, but the types most commonly found in dogs are usually different from those that infect people. The risk of transmission from a dog or cat to a person is considered very low, although good hygiene remains important.
Wash your hands after handling faeces or cleaning contaminated items. Anyone who develops relevant symptoms should contact their GP, particularly if they are very young, elderly, pregnant or immunocompromised.
Recovery
With appropriate treatment and hygiene, most dogs recover fully. Reinfection can occur, especially in multi-dog homes, kennels and environments where contaminated water or faeces remain accessible.
If diarrhoea continues after the prescribed treatment has finished, contact your vet rather than repeating medication without advice.