Understanding Giardia in Dogs

By: Nikki Edwards | Published Sep 12, 2023


Brown and black dog dripping wet and walking in muddy water.


The last thing you want is for your pet to get a serious parasitic infection, but the truth is that it can happen to any dog (and any dog breed). Giardia is a common example, affecting 10% to 30% of canines, according to the Merck Veterinary Manual.

It's essential for dog owners to be aware of Giardia, as it can impact both the health of their pets and potentially their own well-being, making regular veterinary check-ups and preventative measures crucial in maintaining a happy and healthy canine companion.

What is Giardia?

Giardia is a single-celled parasite that lives in your dog’s intestine. It infects older dogs but more frequently infects puppies. Dogs become infected when they swallow Giardia that may be present in water or other substances that have been soiled with feces.

How dogs get Giardia

Your dog has to ingest Giardia in order for them to get the parasite. This can happen by drinking water that has been contaminated by feces or by eating something that has been contaminated by feces, like grass. Since dogs love to chew on things, there are plenty of ways your dog can pick up the parasite, whether it is by chewing on a stick, eating poop, or drinking from a puddle.

Common causes of giardia in dogs

  • Drinking contaminated water
  • Licking contaminated surfaces
  • Eating contaminated food
  • Consuming contaminated feces
  • Sniffing Giardia cysts in feces or on any surface
  • Being in close proximity to other animals that have Giardia

Once the parasite is in your dog’s intestines, your dog can spread the parasite, even if they don’t show any signs of infection. This is worrisome, especially if you have more than one pet in your household. While transmission from dogs to cats and cats to dogs is unlikely, the transmission from dog to dog is certainly a cause for concern. If one of your pets is diagnosed as having a Giardia infection, talk to your vet about the steps you need to take to protect your other pets.

How are dogs affected by Giardia?

Giardia in dogs does not always cause problems, but when it does, the results can be highly unpleasant. Giardiasis is the term for the disease caused by the Giardia infection. Just as in humans, the most common symptom of Giardiasis is diarrhea.

The parasite decreases your dog’s ability to properly absorb nutrients, water, and electrolytes, which leads to diarrhea and weight loss. Diarrhea can be irregular or continual, especially in puppies. Failure to diagnose and treat the disease can lead to severe weight loss and even death in extreme cases. The disease is particularly dangerous for puppies, senior dogs, and dogs with compromised immune systems.


Portuguese Water Dogs standing by water on rocky shore.


Symptoms of Giardia infection in dogs

The best way to determine whether your dog has Giardia or another condition is to call your vet. However, there are several symptoms of infection in dogs of which owners should be aware.

These symptoms include:

  • Diarrhea
  • Flatulence
  • Greasy/fatty stool
  • Weight loss
  • Decreased appetite
  • Dehydration
  • Vomiting
  • Acute diarrhea (very watery diarrhea)
  • Mucus and red blood in diarrhea

Giardia is usually associated with diarrhea, as it is the most common clinical symptom of infection, and infected dogs can produce large amounts of watery feces. Less common symptoms include decreased appetite, abdominal discomfort, and vomiting. In rare cases, dogs may strain to defecate and even pass red blood and mucus in their stool. However, most dogs infected will be asymptomatic, which means they will show no signs of the disease but can pass it on to other animals.

Treatment for Giardia

If you notice that your dog is having diarrhea, call your vet for an appointment, as they will need to conduct several diagnostic tests to determine if your dog has Giardia. If your dog is diagnosed with Giardia, depending on the severity of the case, your vet will discuss a treatment plan tailored to your dog’s needs.

Preventing Giardia

Giardia can’t always be prevented, but you can reduce your dog’s risk of contracting the parasite.

It’s important to prevent your dog from drinking from sources of stagnant water, as streams, puddles, and lakes often contain Giardia — wildlife feces are another source. By keeping them leashed when out on an adventure and making sure they always have access to clean, fresh water, you can protect your dog from consuming potentially contaminated substances.

If you and your dog travel to places with high incidences of Giardia, consider giving your dog filtered or bottled water. This will reduce the risk of infection from their drinking water and prevent the potential spread to human members of your family.

Some quick FAQs:

  • Is there a Giardia vaccine for dogs? A vaccine was developed in the early 2000s to help fight the effects of the parasite in dogs, but its efficacy has been disputed, and it is not generally recommended by the AAHA.
  • What kills Giardia on surfaces? The best solution for use on surfaces is a mixture of bleach and water.
  • How to get rid of Giardia in your yard? Remove waste from your yard, remove standing water, and limit your pet’s use of public outdoor spaces. Consider keeping other animals out of your yard.


Beagle in a red and white collar splashing in water.


Is Giardia contagious to humans?

Luckily, the odds of dogs infecting humans with Giardia are relatively low, although it can happen. Wearing disposable gloves while handling dog poop, and washing your hands thoroughly after, will reduce the already low risk even further. Giardia in humans is commonly transmitted through drinking water, not by our pets.

When in doubt, contact your vet

If your dog shows any signs of Giardia or if you have any other pet parasite concerns, take him or her to the vet right away. It may not necessarily be an emergency visit, but they will need to see a vet to be given the correct medication for recovery.

Interested in more pet parasite prevention tips? Learn how to protect your pet against heartworms.


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