6 Key Facts About Giardia

Six important things you need to know about Giardia

Summary: Giardia can become quite a problem when you don't know what you are dealing with, that's why our very own Dr. Barrientos has answered the top 6 questions about this parasite.

What is Giardia?

Giardia is a very common intestinal parasite, not like a worm, bacteria, or virus, it's a protozoan parasite. It is a unicellular parasite that lives in the intestines of dogs and cats, it can actually affect humans as well and cause gastrointestinal upset, vomiting and diarrhea, and poor growth in dogs. The name of the infection this parasite causes is Giardiasis.

Giardiasis may be a relevant factor for illnesses, especially diarrhea, in both animals and people. However, many dogs infected with Giardia do not get diarrhea, vomiting, or any other signs of illness.

What happens when Giardia is untreated?

Some dogs can get quite sick. These could show variable levels of dehydration, vomiting, and diarrhea. Younger dogs that are in the growth phase can not reach their growth potential and become unthrifty. Occasionally you have some dogs who are able to suppress the Giardia on their own and they don't look like they're sick. Even so, they can be transmitting the Giardia to other dogs in the park, so it is important to test for it by doing a fecal sample and if positive, treat it.

What does Giardia poop look like in dogs?

Generally, a dog that has Giardia will have softish bowel movements. Sometimes it can range from the kind of moderately soft, like melted ice cream all the way to severe diarrhea. So that's the most common sign. Occasionally you will have some dogs that are positive for Giardia that have a normal stool, that is why testing is so important.

How is Giardia diagnosed and treated?

Giardia can be very easily diagnosed through a fecal sample or a stool sample. The treatment involves medication, normally called Fenbendazole, as a first choice, if that doesn't work, we use something called Metronidazole. It can be a very resilient parasite, which may need multiple bouts of treatment to eliminate it. In addition to medication, things like a good digestible diet and probiotics are also effective in controlling the parasite. Some dogs may require follow-up tests and treatments based on their condition and the severity of the infection. All infected pets should be re-tested two to four weeks after completion of treatment.

Can I get Giardia from my dog licking me?

Luckily, the odds of humans being infected with Giardia from dogs are relatively low. This is because there are seven types of this parasite, A through G. Dogs are most commonly infected with types C and D, cats with F, and humans most commonly infected with A and B. Even so, it can happen! So to minimize the risk we recommend washing your hands after handling dog poop and keeping your pet's toys, water, and food bowl clean as a whistle!

How do I prevent my dog and me from getting Giardiasis?

Environmental disinfection and good personal hygiene help prevent accidental spread to humans and other pets if your dog is diagnosed with giardiasis. In particular, people with immunodeficiency, such as AIDS or cancer, or who are undergoing chemotherapy, should exercise extreme care, especially when handling feces or after administering medications.

If you are looking to avoid the parasite, the first thing to do is take your dog to your veterinarian of choice to test and make sure your pet isn't infected. After you are sure Giardia is not an existing problem, good hygiene and easy precautions can help you a lot. Bring water (and a dish) for your dog whenever you are going for long walks. Always wash your hands as soon as possible after handling your dog's stool. Keep their food and water dishes clean, as well as toys and accessories. Remember to do stool tests on your furry friend at least annually.

This article provides a summary view of some aspects you need to know about pets and how to protect them from giardia infections. We recommend you take the time to talk in detail with one of our licensed veterinarians. They will provide the best suggestions and strategies for your pet. For an appointment please contact us at (416) 966-1830.


  • Anna Burke, "The Facts You Need to Know About Giardia in Dogs". American Kennel Club  [source]
  • Ernest Ward, DVM, "Giardia in Dogs". VCA Hospitals [source]
  • Cascade Heights Veterinary Center. "Have Questions about Giardia?" [source]