Giardia in Dogs: 6 Myths About How Dogs Get It and How It Spreads
Giardia in dogs is an infection caused by a tiny, one-celled parasite that lives in the gut. Dogs get it by swallowing giardia cysts. These are hard-shelled eggs of the parasite that pass out in poop. Dogs can swallow them from water, but also from wet grass, soil, other dogs' poop, or their own fur and paws. Once inside, the cysts turn into a new batch of parasites. Within about 5 to 12 days, the dog starts passing new cysts in its own poop, and that is how it spreads. Some dogs get soft, greasy, smelly diarrhea. Many show no signs at all. A vet can test for it and treat it with medicine. Below are 6 common myths about how dogs get giardia and how it spreads, and what is really true.
In this article
- Myth 1: Dogs only get giardia from dirty water
- Myth 2: A dog with giardia always has diarrhea
- Myth 3: You will catch giardia from your dog
- Myth 4: Giardia dies fast outside the body
- Myth 5: Once the medicine is done, it is gone for good
- Myth 6: Only neglected dogs get giardia
- Giardia myths vs. facts at a glance
- Frequently asked questions
Myth 1: How Do Dogs Get Giardia? Not Just From Dirty Water
The truth: Water is only one way in. Giardia cysts pass out in the poop of a sick animal. From there, they can end up in puddles, streams, and lakes. But they also stick to grass, soil, and anything else that touches poop.
VCA Animal Hospitals says dogs swallow cysts from water, soil, grass, or poop. A dog can also lick cysts off its own paws or fur. That is how a dog can pick it up again after it seemed to get better.
Common ways dogs swallow cysts
- Drinking from puddles, ponds, or shared water bowls
- Sniffing or licking grass where other dogs have pooped
- Eating poop, which many puppies do
- Licking cysts off their own paws, fur, or rear end
- Rough play with an infected dog
Myth 2: What Are the Signs of Giardia in Dogs? Diarrhea Is Not a Sure Thing
The truth: Lots of dogs carry giardia and look fine. The Western College of Veterinary Medicine says many infected dogs show no clear signs at all. Those dogs can still pass cysts and spread it.
When a dog does get sick, the main sign is diarrhea. It is often soft, pale, greasy, and very smelly. It may have mucus in it. Some dogs also have gas, throw up, lose weight, or seem tired. Puppies and dogs under stress tend to get the worst of it.
How common is it? The Companion Animal Parasite Council (CAPC) says that about 15.6% of U.S. dogs with signs like diarrhea tested positive. In a study of dog parks in Calgary, Canada, it turned up in 24.7% of the dogs.
Myth 3: Can Humans Get Giardia From Dogs? The Risk Is Low
The truth: It can happen, but it is not common. Giardia comes in different types. Scientists call them "assemblages." Dogs mostly carry types C and D. Those types are rarely found in people. Reviews of the research say the risk of a pet dog passing giardia to a person is thought to be low.
Low is not zero, though. Now and then, dogs carry the types that people get too. So keep it simple. Wash your hands after you pick up poop. Take extra care if someone in your home is very young, very old, or has a weak immune system.
Myth 4: How Does Giardia Spread? It Lasts a Long Time Outside the Body
The truth: Giardia cysts are tough. The Cornell University College of Veterinary Medicine says they can last for months around your home and yard.
Cold, damp places help them last longest. In one 1999 lab study, cysts kept in cold water (about 39°F) could still cause infection after 11 weeks. In warm water (about 77°F), they lost that power within 2 weeks. Freezing killed them within a week.
That is why giardia spreads so well where lots of dogs share space. Think dog parks, day cares, kennels, and shelters. One sick dog can leave cysts behind for the next dog to find.
Myth 5: Once the Medicine Is Done, Giardia Is Gone for Good
The truth: Dogs often catch it again from cysts left on their fur or in the yard. Your vet will usually prescribe fenbendazole, metronidazole, or both. CAPC lists courses of about 3 to 5 days for fenbendazole and 5 to 8 days for metronidazole. Your vet will pick the right drug and dose for your dog.
The medicine is only half the job. Here is what vets often suggest to stop it from coming back:
Steps to help stop reinfection
- Bathe your dog on the last day of treatment. This washes off cysts stuck to the fur, mostly around the rear end.
- Pick up poop right away and throw it in the trash.
- Clean hard floors, bowls, and crates. Cornell says common home cleaners and steam cleaning work best.
- Wash bedding and toys in hot water.
- Let the sun help. Cornell says cysts on a lawn are killed by drying out in direct sunlight.
- Wipe paws after walks, before your dog curls up on the couch.
One more tip: some giardia tests can stay positive for a while after treatment. CAPC says those tests should not be used to decide if treatment failed. If signs come back, ask your vet which test makes sense.
A sturdy coir mat that marks the spot where every walk ends with a quick paw wipe.
Myth 6: Only Neglected Dogs Get Giardia
The truth: Giardia is common in well-loved dogs, too. CAPC says dogs in shelters, kennels, and breeding sites are more likely to carry it. Puppies are at higher risk as well. That is because so many dogs share the same space and the same ground.
So if your new rescue dog tests positive, it does not mean the rescue did a bad job. It is one of the most common things vets find in newly adopted dogs and foster dogs. A good rescue will tell you about it and help you plan treatment. If you are thinking about taking in a dog, our guide on how to foster a dog covers what rescues usually pay for, including vet care.
Not every case of puppy diarrhea is giardia. Bloody diarrhea, nonstop vomiting, or a very tired puppy can mean something more serious. Check our list of signs of parvo in puppies and call your vet right away if you see them.
Should a dog with no signs be treated?
Not always. Most of the CAPC board thinks dogs with no signs may not need treatment. Your vet may still treat if your dog lives with other pets or with a person who gets sick easily.
Giardia in Dogs: Myths vs. Facts at a Glance
| Myth | Fact |
|---|---|
| Dogs only get it from dirty water | Dogs swallow cysts from water, grass, soil, poop, and their own fur |
| A dog with giardia always has diarrhea | Many infected dogs show no signs but can still spread it |
| You will catch it from your dog | Dogs mostly carry types C and D, which rarely infect people |
| It dies fast outside the body | Cysts can last for months, longest in cold, damp places |
| Medicine alone ends it for good | A bath and a good cleanup help stop it from coming back |
| Only neglected dogs get it | It is common in puppies, shelters, kennels, and dog parks |
Sources: Companion Animal Parasite Council, Cornell University College of Veterinary Medicine, VCA Animal Hospitals, CDC.
Frequently Asked Questions
What does giardia poop look like in a dog?
It is often soft or runny, pale, greasy, and very smelly. It may have mucus in it. Some dogs with giardia have normal poop, so only a vet test can tell for sure.
How long does giardia take to go away in dogs?
Most dogs feel better within a few days of starting medicine. A full course often runs about 3 to 8 days, based on the drug. Some dogs need a second round, mostly if they pick up cysts again at home.
Can giardia go away on its own in dogs?
Sometimes, in a healthy adult dog with no signs. But a dog with diarrhea should see a vet. Puppies can lose fluids fast, and other illnesses can look like giardia.
Is giardia contagious to other dogs?
Yes. Dogs pass it through poop. Other dogs pick it up by sniffing, licking, or drinking where cysts are. Keep a sick dog away from dog parks and day care until your vet says it is okay.
How do vets test for giardia?
Vets look for cysts in a poop sample, or use a test that finds giardia proteins. Dogs only shed cysts some of the time, so your vet may ask for more than one sample.
For the Dog Person on Cleanup Duty
Baths, mopping, and extra yard runs. A warm hoodie makes the job a little nicer.
A cozy everyday hoodie for chilly fall walks and late-night yard trips.
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