Giardia in Dogs

What Is Giardia?

Giardia is a single-celled parasite with whip-like tails (flagella) that lives in the small intestine.^1,5 It forms tough cysts that pass out in the stool. These cysts can infect another animal right away, and only a few are needed.^1,8

Giardia comes in several genetic types, called assemblages. Dogs mostly carry types C and D, which are adapted to dogs. People are almost always infected with types A or B.^8,5,12

How Do Dogs Get Giardia?

• Drinking contaminated water from creeks, ponds, puddles or shared outdoor bowls^3,4
• Sniffing, licking or eating feces, or playing in soil or grass where infected dogs have pooped^3,1
• Licking their own coat after it touched contaminated ground or stool, which is also how dogs reinfect themselves^3,1
• Living in groups, such as kennels, shelters, breeding facilities and doggy daycare, where it spreads easily^13,10

Cysts survive for weeks to months outdoors, especially in cool, damp places, and dry out and die faster in warm, sunny conditions.^3,5 In a 2022 park study, dogs whose owners reported routine deworming were just as likely to have Giardia as other dogs.²

How Common Is Giardia in Dogs?

Figures vary widely depending on the dog's age, where it lives and which test is used. CAPC reports that about 6% to 16% of US dogs tested are positive, with the higher figure in dogs that have signs.¹ Rates are much higher in puppies, in dogs from shelters and in kennels.^2,9,12 Sensitive antigen tests find far more infections than a standard stool float, so newer studies often report higher numbers.^2,14

Signs of Giardia

Most infected dogs look completely healthy.^1,5 When signs appear, they're most common in puppies, stressed dogs and dogs with weak immune systems, and can include:^8,3

• Soft, pale, greasy-looking stool with mucus and a strong smell. Watery diarrhea and blood are less common.^5,6
• Diarrhea that comes and goes, sometimes for weeks^1,8
• Weight loss or poor growth, and sometimes vomiting, poor appetite or tiredness^8,4

See Giardia symptoms in dogs for what Giardia poop looks like and how vets test for it.

Can Humans Get Giardia From Dogs?

It's possible but unlikely. The CDC says "you are unlikely to get a Giardia infection from dogs or cats," because the type that usually makes people sick is different from the type dogs carry.³ CAPC notes that dog-to-human spread hasn't been conclusively shown in North America.¹ A small share of dogs do carry the human types: about 4% to 8% of positive results in recent US and German studies, though one Italian study found a quarter.^7,9,15

You can still pet and cuddle your dog. Wash your hands after touching your dog, its bedding or its stool, bathe your dog to remove cysts from its coat, and pick up feces promptly.^3,4 Take extra care if anyone at home is very young, elderly, pregnant or has a weak immune system. In those homes, vets may test which type the dog carries and treat even a dog without signs.^1,8

Treatment and Outlook

Dogs with diarrhea are treated with a prescription course of antiparasitic medicine, sometimes two medicines together, plus a bath with shampoo at the end of treatment and thorough cleaning.^1,4 Most dogs' diarrhea improves with treatment, but no medicine works every time, and Giardia often returns because the dog picks it up again from its surroundings.^7,1 Over-the-counter remedies aren't approved for Giardia.³ See Giardia treatment for dogs for treatment, how long it lasts and how to clean your home and yard.

Preventing Giardia

• Pick up feces right away, at home and on walks.^1,4
• Bring fresh water on outings so your dog doesn't drink from ponds, puddles or shared bowls.^3,12
• Remove standing water in your yard and keep water bowls clean.^3,13
• Keep new puppies separate from other dogs until they've had a vet check and stool test, especially puppies from shelters, pet stores or large breeders.^9,10

Frequently Asked Questions

Can a dog fight off Giardia without treatment?

Many dogs carry Giardia without ever getting sick, and guidelines usually don't treat healthy dogs. Dogs with diarrhea should be treated.

How contagious is Giardia to other dogs?

Very. Cysts are infective as soon as they're passed and can survive for weeks to months, so other dogs in the home often get it too.

Can I cuddle my dog if it has Giardia?

Yes. The risk to people is low. Wash your hands afterward and bathe your dog to remove cysts from its coat.

How long does Giardia last in dogs?

Diarrhea usually improves during treatment, but some dogs need a second course, and dogs can be reinfected from the environment.

Is Giardia the same as coccidia?

No. Both are single-celled gut parasites that are common in puppies, but they're different organisms with different treatments. See coccidia in dogs.