What Is Giardia In Dogs?

By Chyrle Bonk, DVM April 20, 2020

You and your dog went for a wonderful hike in the woods over the weekend. This morning you had to clean your best friend’s diarrhea off of the living room carpet, kitchen floor, and dog bed, while your dog is lying in the corner groaning with a bloated stomach. You’re probably thinking, what just happened? The cause of your dog’s discomfort could be Giardia.

What Is Giardia In Dogs?

Giardia is the causative agent of giardiasis, an intestinal infection of animals and humans. Giardia is a microscopic parasite called a protozoa. Giardia isn’t like other intestinal parasites, such as worms or bacteria, rather a protozoa is a single-celled organism capable of living in the intestines and causing diarrhea. Giardia comes in many different species and genotypes. Dogs are most commonly infected by Giardia duodenalis types C and D.

These little protozoa exist in two forms. Trophozoites live strictly in the intestine of its host. Cysts on the other hand, are shed in the infected animal’s feces with the ability to survive in the environment and infect other animals.

How Do Dogs Get Giardia?

In order for a dog to get Giardia, they need to eat, drink, or inhale a viable cyst. This can either be through direct contact with an infected critter or through contact with infected feces or environment. Once the cyst is able get in your dog by evading their immune system, it will travel to the intestine and transform into a trophozoite that attaches to the intestinal wall. Afterwards, the trophozoite will start to syphon nutrients away from your dog. If enough trophozoites infect your pup, the damage done by their attachment to the intestinal wall can lead to diarrhea, weight loss, and the other clinical signs.

Giardia trophozoites divide to reproduce. Some of these will revert back to the cystic form and be passed in your dog’s feces, ready for the next critter to come along. These cysts can live for several weeks in the environment, especially if it’s cool and wet. This makes water an ideal habitat and a good reason that most dog exposures come from infected water. However, your dog drinking from a stream isn’t the only way they can get Giardia. Coming into contact with a bunch of animals at places like a boarding facility or a dog park poses a huge risk as well, especially if these places are unhygienic.

However, steering clear of the dog park and the great outdoors doesn’t mean your dog will be in the clear. All they have to do is come in contact with an infected animal or their feces, even feces that is a couple of weeks old. So, your pup could come in contact with Giardia on any routine walk or even when on a puppy playdate.

Is Giardia Contagious To Humans And Other Animals?

You’ve probably heard of “Traveler’s Diarrhea” or “beaver fever,” which are common terms for Giardia in humans. It’s true that Giardia isn’t limited to dogs. In fact, many animal species, such as cats, cows, horses, pigs, sheep, mice, birds, frogs, and many others can suffer from Giardia. But there are many different species of Giardia and seven different types of Giardia duodenalis, the species that infects our pups and other pets. While all of these types of Giardia can cause disease in various species of animals, they tend to be species specific. This means that the type of Giardia that infects your dog won’t infect you or your pet cow. However, it can infect other dogs and your kitty, so be sure to quarantine any critters with known Giardia infections.

What Are The Symptoms Of Giardia In Dogs?

Younger dogs tend to show more severe symptoms when infected with Giardia simply because of an immature immune system. However, when trophozoite numbers are high enough, any age animal can present with acute (sudden) diarrhea. Again, this diarrhea comes about because of the damage to the intestinal wall when the feeding Giardia attach. The more trophozoites that attach, the more damage and the more severe the symptoms. The diarrhea can be intermittent and chronic, meaning it comes and goes for several weeks or even months. The texture can range from soft to extremely watery. It can be foul smelling, bloody, green tinged, or mucous like. Occasionally, dogs may vomit, be lethargic, bloated, or show abdominal discomfort.

In cases of chronic Giardiasis, dogs may experience gradual weight loss as well. Infected dogs may also not show any symptoms and instead be silent carriers that pass Giardia on to other dogs without showing any signs that they’re even sick.

How Is Giardia In Dogs Diagnosed?

Diagnosis of Giardia in dogs should be done by a veterinarian. They can perform a fecal float to rule out other parasitic causes of diarrhea and a fecal smear to try to detect Giardia itself. Since the cysts are shed inconsistently, it may be difficult to “catch” them in the feces so a sample may need to be sent to a lab for further analysis. Some cases of Giardia may be presumptively diagnosed based on history, symptoms, and response to treatment.

What Are the Treatments For Giardia In Dogs?

The treatment for Giardia includes anti-parasitic drugs similar to what would be used for other intestinal parasites. The treatment will need to be given for up to 10 days, or longer for more difficult cases. Be sure to give prescribed medications in full even if your pup’s diarrhea gets better within a few days. Not following your veterinarian’s guidelines may increase your dog’s chance of reinfection. Other supportive treatments may be necessary if your dog is dehydrated or weakened from severe diarrhea. Feeding a highly digestible diet while your pup has diarrhea can also help their digestive tract heal during treatment.

Frequent bathing and feces pick-up will help reduce the risk of recontamination and spread to other animals. You will want to disinfect possibly contaminated areas by using a bleach solution or ammonia compound. Your dog should be retested for Giardia two to four weeks following the end of treatment to be sure that reinfection didn’t occur.

Can Giardia In Dogs Be Prevented?

Giardia can live just about anywhere in the environment and for possibly up to a couple of months if the conditions are right. With this in mind, it’s hard to completely eliminate it from your dog’s surroundings, but you can help reduce their chances of becoming infected with some proper hygienic precautions. Pick up feces immediately and don’t let your pup mingle with other dog’s feces. Wear gloves and wash your hands after picking up feces to further protect your pup. Use boarding and grooming facilities that you know are clean and that provide private spaces for your dog. When outdoors, avoid letting your dog drink from streams or other natural water sources.

Are There Home Remedies For Giardia?

Even though Giardia is treated with common anti-parasitics, these are not over-the-counter products. The dewormers that you can buy at the pet store are not effective. You need products that are available exclusively through a veterinarian under a prescription.

However, you can help prevent reinfection or infection of other animals at home by cleaning up feces, quarantining infected animals, and frequent bathing of critters and disinfecting of common spaces. You can also provide supportive treatment to prevent dehydration and feed a quality, highly digestible food so that your dog’s GI can heal.  

When Should Your Dog See A Veterinarian For Giardia?

No one likes to clean up diarrhea, so many dog parents will take their pup to the vet after the first diarrheal mishap. That’s perfectly fine. Other dog parents may choose to wait until their dog has had diarrhea for a couple of day before bringing them in. That’s okay too, it just gives your dog a higher chance of spreading Giardia to others and for them to become dehydrated if the diarrhea is severe enough.

Generally speaking, your dog should see a vet if you suspect Giardia as soon as possible to reduce the likelihood of spreading it. However, most dog parents aren’t going to jump to a suspicion of Giardia unless they know their dog was in contact with an infected dog. With that in mind, anytime your dog experiences foul smelling diarrhea that lasts longer than 24 hours, is bloody, mucous like, or if they’re lethargic, then they should see a vet.


Giardia is a nasty little parasite that your dog may experience in their lifetime. It is hardy and has the ability to survive in the environment for prolonged periods of time, making exposure hard to avoid. You can reduce your dog’s risk of developing smelly, possibly bloody and mucous like diarrhea caused by Giardia by cleaning up their feces and keeping an eye on what they’re getting into and who they’re mingling with. Giardia should only be diagnosed and treated by a veterinarian. Never give your dog any medication that hasn’t been specifically prescribed for them. Enjoy the outdoors with your pup, just don’t let them drink from streams and ponds where Giardia could be a problem.

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