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Giardia in dogs: Causes, symptoms, treatment, and prevention

Dog with giardia

If your dog has been having tummy issues resulting in diarrhea and you can’t figure out the cause, they could have Giardiasis, an infection caused by tiny parasites called Giardia. Giardia is among the most common intestinal parasites reported in dogs, but they can wreak havoc on your dog’s digestive system. 

Here’s everything you should know about Giardia in dogs, including how a veterinarian identifies them and Giardia treatments. 

Table of contents 

What is Giardia? 

Giardia is a microscopic, single-cell parasite that causes an intestinal infection in humans and animals called Giardiasis. The Giardia parasite has two forms. The mature parasites, or trophozoites, live in the small intestine where they multiply and eventually become cysts. Cysts are the infective stage and are shed into the feces of the infected animal. They can survive for several weeks in the environment as cysts, and when they are ingested by an unsuspecting host, they turn into trophozoites and repeat the life cycle. 

Because these parasites can survive for extended periods of time outside of a host and many dogs infected with Giardia do not have symptoms, Giardia is considered highly contagious, and infections are common in dogs. Those who do exhibit symptoms can experience weight loss and diarrhea, sometimes severe enough to cause death. 

How do dogs contract Giardia? 

A dog becomes infected with Giardia when they ingest the cyst stage of the parasite, which then attaches to the intestinal wall to feed on its host. Eventually, the dog passes infectious cysts in their stool. In dogs, the time it takes from ingestion of cysts to passage in feces is between 5 to 12 days. 

Giardia parasites can be transmitted by eating or sniffing the cysts from contaminated surfaces like grass at the park, or by drinking contaminated water. Since dogs explore the world around them by putting things in their mouths, there are plenty of ways your dog can pick up the parasite in their environment, whether it is by chewing on a stick, eating (or just sniffing) poop, or drinking from a puddle. 

Giardiasis is a common occurrence in environments that are densely populated, such as kennels, pet stores, or animal shelters. It is also important to note that your dog’s monthly flea, tick, and heartworm preventatives do not protect them from Giardia, so pet parents need to be very vigilant. 

It is very common for young puppies to have Giardia, and many new pet parents discover that their puppy has an infection when they first bring them home upon adoption. Keeping water clean of feces is challenging with a litter of puppies, which allows Giardia parasites to thrive. Puppy parents should have their new family members tested for Giardia during their first check-ups with the veterinarian, even if they aren’t showing symptoms. Early detection can not only prevent complications from more severe cases of Giardia, but can also help keep other pets healthy. 

Dangers of Giardia 

Giardia cysts found in the stool of a healthy adult dog without diarrhea are generally not a cause for concern. In fact, the Parkway Veterinary Emergency Clinic notes that most adult dogs are considered carriers of Giardia even if they do not show symptoms. 

However, in puppies, senior dogs, and those with compromised immune systems, Giardia may cause severe, watery diarrhea that may be fatal if left untreated. Giardia parasites inhibit your dog’s ability to properly absorb nutrients, water, and electrolytes. This can lead to diarrhea, dehydration, weight loss, and even death. 

Giardia symptoms 

Giardia in dogs does not always cause clinical signs, but when it does, symptoms are very unpleasant. The most common symptom of Giardia is diarrhea, in which case the stool may range from soft to watery, often has a greenish tinge to it, and occasionally contains blood and mucus. 

Additional symptoms can include: 

  • Weight loss 
  • Failure to gain weight 
  • Loss of appetite 
  • Vomiting 
  • Dehydration 
  • Poor coat appearance 
  • Lethargy 

How long do Giardia parasites survive? 

Part of what makes Giardia so contagious is that the parasites can live in the environment, outside of a host. So, how long is a contaminated surface considered contaminated? 

  • Giardia can survive for several months in cold water or moist soil. 
  • Giardia can survive longer in water at colder temperatures (i.e., lake or puddle water during the winter, refrigerated water) than at warmer temperatures (i.e., tap water, river or puddle water in summer). 

Can your infected dog give you Giardia? 

Although the odds of a person being infected with Giardia from dogs is relatively low, it is still possible for these parasites to pass from dogs to humans. If your dog has contracted Giardia, environmental disinfection and good personal hygiene are important to prevent accidental spread to you and your family. You should be sure to wash your hands after handling dog poop.  

Diagnosing Giardia 

If your veterinarian suspects that your dog has contracted Giardia, they will likely take a stool sample for testing. Some Giardia tests are available for in-clinic use while other tests require submittal to a laboratory. Many cases are presumptively diagnosed on the basis of medical history and clinical signs suggestive of Giardiasis. 


If you suspect your dog is suffering from Giardia, contact your veterinarian immediately. Giardia requires treatment with prescription medications. The most common drugs used to kill Giardia are fenbendazole and metronidazole, which are normally given to dogs for three to 10 days. 

Supportive treatment with other drugs may be needed if your dog has dehydration or severe diarrhea. A low-residue, highly digestible diet may help minimize loose stools during treatment. Food should be bland and easy on the digestive system—try boiled chicken, rice, and pumpkin. Infected pets should be re-tested two to four weeks after completion of treatment. 

Because Giardia cysts are infective immediately when passed into the environment, feces should be removed quickly and disposed of. Infected animals should also be bathed regularly to remove cysts from their coat. Giardia cysts are susceptible to drying out, so try to keep your environment as dry as possible. Thoroughly clean your dog’s living and sleeping areas and then allow the areas to dry out for several days.  

How to prevent Giardia 

While we can’t always control every aspect of our dog’s environment, there are some things owners can do to prevent Giardia in dogs. 

The most important thing is making sure your dog always has access to fresh, clean water in a bowl off the ground. This will reduce the chances of them lapping up water from potentially infected puddles or public water bowls at the dog park. 

You can also try avoiding places where there are large amounts of dog traffic and feces. Your dog can contract Giardia from simply licking their paws after they’ve stepped on a contaminated surface. 

Any health or medical information in ElleVet blogs is from a variety of public and reputable sources. This information is intended as an education resource only and is not a substitute for expert professional care.