Giardia in Dogs: A Straightforward Guide

By Chelsea Hunt-Rivera / May 7, 2018
Giardia in Dogs

You’re on your afternoon walk with your fur baby when you notice that something is off with their “business” … diarrhea. You know that in humans, diarrhea can result from a number of reasons from serious infections to eating something that didn’t necessarily agree with your stomach. The reasons are actually comparable in dogs. Differing the two is that dogs can’t tell us whether they snuck a bite of spoiled trash food or if there’s something very, very wrong. Let’s say you wait a day and your dog’s diarrhea situation clears up. It looks like Fido is back to normal. Then, seemingly out of nowhere, it begins again. You might have a case of Giardia in dogs…

What is Giardia in Dogs?

Giardia in Dogs

Giardia Duodenalis (or simply Giardia) is a protozoan, or single-celled, parasitic species. It is important to note that Giardia is not a worm, virus, or bacteria. You may also hear Giardia referred to as Giardia Intestinalis or Giardia Lamblia.

There isn’t a ton of information available of the parasite itself, but we do know that it exists everywhere and in several different types.

There are eight genotypes of Giardia that currently exist. These genotypes are labeled A through H. It is possible we wake up tomorrow and another two genotypes are discovered. Scientists are constantly finding new information on the parasitic species.

Dogs are most commonly affected by Giardia C and D and humans by Giardia A and B.

Cats are commonly affected by Giardia F. Cloven-hoofed animals carry genotype E, rats carry G, and genotype H has been found in seals.

Furthermore, genotypes A and B have also been found in dogs and cats, along with other animals, making scientists consider them as broad host-specificity and potentially zoonotic. (Zoonotic means the disease has the ability to transmit from animals to humans)

What is Giardiasis?

Giardiasis is an intestinal infection resulting from the one-celled organism, Giardia. While more prevalent in certain areas, The Center for Disease Control (CDC) states that Giardiasis exists in humans and animals worldwide.

Giardia CystsGiardia in Dogs small intestine

The lifecycle of the Giardia has two stages. The mature parasites, or trophozoites, live in the small intestine and multiply, eventually causing cysts to form. When the infected cysts are shed in the feces of the animal, they are able to be ingested by the next host, thus continuing the cycle of Giardiasis.

The cystic form of the Giardia parasite that is shed in feces can survive for several months, particularly in wet environments. The high survival rate of the disease contributes to the high volumes in which it is prevalent in some parts of the world.

Cause of the Giardia Infection

Giardiasis occurs when an animal ingests the infected Giardia parasite in its cyst stage. The ingestion can occur by drinking water or eating something, like grass, that has been infected by contaminated feces. Since dogs love putting things in their mouths that they shouldn’t, there are a plethora of ways that Giardiasis can occur.

When the dog ingests the giardia cysts and they move to the dog’s intestines, the dog can transmit the disease, even without showing symptoms of having it.

Giardia is a common occurrence in environments with dense populations such as kennels, shelters, and pet stores.

Additionally, if a Giardia-positive dog licks its backside and then licks another animal or even human, the disease has a possibility of transmission. Love isn’t always pretty.

In dogs, it usually takes 5-12 days from the ingestion of the cysts to the passing of the cysts in the feces to occur.

Beaver Fever

Outdoor enthusiasts may have heard of the term “beaver fever.” Beaver fever is, in fact, another word for Giardiasis. The catchy term comes from the idea that humans could contract the clinical signs of Giardia (diarrhea, vomiting, fever, etc.) from drinking contaminated water from where a beaver defecates.

Of course, beavers are not the only animals that can transmit the disease. It more so serves as a reminder to be mindful of what you are drinking and eating.

Giardia Symptoms

A lot of the time, Giardia is asymptomatic, meaning it doesn’t have symptoms.

The most common symptom of giardia is diarrhea. Diarrhea may be mild or severe or may not occur at all. The stool is often green in color and is occasionally bloody. Diarrhea may happen intermittently (on and off), be acute (sudden-onset), or chronic (long-lasting).

Because diarrhea can happen intermittently, pet owners may easily overlook the possibility of Giardia. The pet owner assumes that their dog’s sour stomach is due to a meal that didn’t agree with the dog and therefore, the dog goes undiagnosed.

Other clinical signs include:Giardia in Dogs fever

  • Vomiting
  • Weight loss (from the continuous vomiting and diarrhea)
  • Dehydration
  • Poor coat appearance
  • Decreased appetite
  • Foul smelling stool
  • Stool with mucous
  • Abdominal pain
  • Lethargy
  • Fever

The Dangers of Giardia Parasites

Due to the fact that Giardia can go on for weeks, months, and sometimes even years without a proper diagnosis, there are a number of secondary conditions that may result from the infection and the Giardia parasites continuing to live and reproduce in the dog.

First, Giardiasis in dogs can result in acute, debilitating bouts of bloody diarrhea.

Also, while most dogs with Giardiasis do not lose their appetites, but in chronic, undiagnosed cases, the dogs will lose an extreme and dangerous amount of body weight.

Additionally, infected dogs will experience digestive problems. This is due to the fact that the Giardia infection inhibits the body from absorbing the nutrients.

Furthermore, the parasitic disease can cause severe damage to the infected dog’s intestinal wall and intestinal tract.

Studies show that this particular parasite is responsible for many chronic cases of gastrointestinal inflammation as well as being at the root of Inflammatory Bowel Disease.

Giardia in Puppies

The Giardia disease is common in puppies whose immune systems are still developing. Because puppies are so small and do not have the excess weight they can live without, the disease is often deadly.

It is important to mention, while diarrhea also the most common sign of the Giardia parasite in puppies, it is also a sign of other deadly illnesses including parvovirus.

If your puppy is having repeated bouts of watery diarrhea, seek medical attention immediately. Your vet will be able to rule out parvo and treat whatever is causing the symptoms at hand.

Diagnosing Giardiasis in Dogs

While possible, diagnosing giardia in dogs can be relatively difficult.

Pet owners shouldn’t bother looking themselves for differences in their dog’s feces. The Giardia parasite is microscopic and unable to detect without special tools.

There are a few tests that veterinarians use in order to diagnose Giardia in dogs.

Giardia in Dogs fecal sample

Direct Smear Test

A direct smear test requires a fresh stool sample (no less than 30 minutes old) in order to detect a 1st stage trophozoite.

Fecal Flotation Test

An accurate diagnosis requires a sample of fecal matter containing the Giardia cysts. The problem is that the cysts don’t shed every time your dog does its business. Therefore, your dog may have the disease but the stool sample shows they do not.

Fecal ELISA Test

If your dog is having unexplainable bouts of diarrhea, you may want to look into your vet performing a fecal ELISA test. The ELISA test presents a more accurate diagnosis because it detects Giardia antigens present in the animal’s body. A typical fecal test only detects giardia cysts in a stool sample and can result in a misdiagnosis. The problem with the ELISA test is that it often requires being done at least three times in one week period.

Blood Test

Scientists have recently developed a blood test that is able to detect Giardia cysts and accurately diagnose Giardia. The blood tests are far more accurate than fecal sample testing, but they may not be available everywhere quite yet. Pet owners should ask their vet for more information on what diagnostic tools are available.

Giardia in Dogs blood test

Giardia Treatment

Luckily, treating Giardia in dogs is pretty straightforward, although in some cases it can be a bit tedious.

If your dog receives a positive diagnosis for Giardia, your vet will most likely prescribe an antiparasitic medication such as fenbendazole and metronidazole. Your vet may prescribe one or other or a combination of both for approximately three to ten days.

It’s also possible that your vet will prescribe metronidazole first, re-test the dog, and if the parasitic infestation doesn’t respond efficiently, they will then prescribe fenbendazole.

If your dog is facing severe dehydration or has any secondary ailments resulting from the Giardia disease, they will receive treatment for that as well.

Additionally, your vet may recommend a low-residue, easily digestible diet to decrease the number of loose stools during the treatment process.

New Problems Arising with Treating Giardia

Giardia in Dogs

Unfortunately, the treatment of Giardia is becoming more and more difficult as more dogs are becoming resistant to common anti-protozoal medications.

Because of the fact that dogs are becoming more resistant to medications, it is becoming more common that the first round of the drugs will not work and they will have to have a second round of treatment. Your dog may stop showing signs of carrying the disease, yet still carry it and be able to transmit it to others.

For this reason, among others, it is imperative that all infected dogs are retested two to four weeks after the complete treatment in order to ensure that the infection has cleared and your dog is no longer able to spread the illness.

Also, it is important to note that pregnant dogs cannot use conventional medical treatment as it can cause birth defects. Pet owners should let their vet know if there is any possibility that their dog may be pregnant.

Preventing Giardia in Dogs

We fully understand that pet owners are unable to control every single aspect of their dog’s environment. As much as we want to keep an eye on their every move, dogs have a way of getting into things they shouldn’t.

With this being said, there are some things you can do on a day-to-day basis that will largely limit your dog’s susceptibility to contracting Giardia. If your dog happens to test positive for the illness, there are ways to make sure your dog doesn’t pass it to another dog.

First, and perhaps most important, always make sure that your dog has access to fresh, clean water. Having clean water at home will reduce the chances of your dog trying to drink the water from potentially infected puddles. If you happen to live in a place where Giardia exists in the tap water, make sure to purchase filtered water for both you and your pup. Some pet owners may boil the water to kill off the Giardia cysts. This method works, but be sure to allow it to cool before serving it!

Also, you may have seen signs in your city reminding pet owners to pick up after their dogs. This is not only because no one wants a feces infested neighborhood, but because feces carry disease. In order to do your part in the prevention of Giardia, pet owners should be sure to always clean up after their dogs right away. Paying attention to hygiene will not only protect your pup, but it will also protect you and anyone else playing in your yard.

Being Aware of Your Surroundings

Additionally, pet owners should be aware of areas where Giardia has a higher presence. If you want to avoid your dog contracting the disease, you may want to consider limiting their exposure to places like boarding facilities, groomers, doggy day-cares, and unkept dog parks. This is not to say that many facilities don’t take the necessary prevention measures to disinfect, but you’ll want to be sure that’s the case before dropping your dog off.

Pet owners should also make sure that their dog isn’t drinking out of communal water bowls in public places as contamination is often prevalent in these circumstances.

Furthermore, do not allow your dog to drink from puddles, rivers, ponds, lakes, streams and other places where infected animals may have defecated in the water source.

Of course, never let your dog eat its own or another dog’s feces. Hopefully, this goes without saying.

All in all, limiting your dog’s potential exposure to Giardia will ultimately reduce the possibility of contracting it.

Giardia in Dogs

Prognosis of Giardia in Dogs

The prognosis of Giardia in dogs is good in most cases. However, debilitated and geriatric dogs along with very young puppies with susceptible immune systems are at an increased risk of secondary conditions, complications, and even death.

While it may seem like an upset stomach that will pass, pet owners should always seek medical attention in order to ensure that the disease is handled properly, doesn’t cause additional issues, and doesn’t affect any other animals.

Giardia in Humans

We have briefly mentioned throughout the article that Giardia can also occur in humans.

Individuals who most commonly contract the disease are those who inadvertently consume contaminated water. Campers and other outdoor enthusiasts may think the spring water they are slurping up or washing their face with is “clean enough.” However, in actuality, defecation by an animal carrying Giardiasis may have led to the water’s contamination.

There are several other protozoan parasites that humans and animals may unknowingly consume that can cause disease of the intestine. These parasites include:

  • Coccidia
  • Cryptosporidia
  • Toxoplasma

Preventing Giardia in Humans

While we can’t always control our environment, humans are able to prevent Giardia by ensuring they have enough filtered water to last the entirety of their outdoor excursion. When drinking water that hasn’t been filtered, one has to realize the amount of traffic that the water has seen. From chemicals to animal fecal matter, it is extremely important to make sure you do everything possible to avoid ingesting anything that can lead to a serious ailment. Besides, no one wants to have diarrhea on a camping trip.

With that in mind, if you don’t feel comfortable drinking the water, you shouldn’t give it to your pup.

If your dog is accompanying you on your outdoor excursion, bring ample filtered water for the both of you.

The Transmission of Giardia in Humans

Humans can also contract the disease from eating contaminated food. Yet, this way of contracting Giardia is less common because the heating process kills the parasite. However, eating uncooked fruits or vegetables that have been contaminated with fertilizer is a way in which the disease can be transmitted via food source.

Sadly, doctors have found the Giardia parasite in the small intestines of a lot of people living in third-world countries. This is a result of the lack of necessary means to clean their food and purify their water.

Here are several ways that Giardia can transmit to humans:

  • Drinking water that is contaminated with Giardia cysts
  • Eating uncooked fruits and vegetables that were washed with contaminated water
  • Eating uncooked fruits and vegetables that were harvested using contaminated fertilizer
  • Touching a contaminated diaper and improperly washing your hands
  • Having direct contact with another person or animal that has the infection

Here are people who are more susceptible to contracting the disease:

  • Day care workers
  • Children in day care
  • People who travel to developing countries
  • Campers who drink unfiltered water

Giardia is Zoonotic

The last thing we want to mention again about Giardia in humans is that scientists consider it to be zoonotic. If a disease is zoonotic, it can transmit from animals to humans. Although the chances of a human contracting Giardia from their infected dog are quite small, the possibility does exist.

If your dog contracts the disease it is crucial to keep your home as clean as possible. By disinfecting surfaces daily, you can ensure that you don’t get sick. It will also help prevent your dog from contracting the disease again.

Giardia in Dogs zoonotic

Treating Giardia in Humans

In most cases, Giardia in humans will resolve on its own without medical intervention. However, if the case of Giardia is severe, a doctor may prescribe antibiotics.

Interestingly enough, the same medication that is used to treat dogs with Giardia (Metronidazole ) is also used to treat humans with Giardia. While Metronidazole needs to be taken for five to seven days, the drug Tinidazole is also able to treat Giardia in a single dose.

Giardia in Dogs – A Nasty But Preventable Illness That Pet Owners Should Know About

No pet owner likes playing a guessing game when it comes to whatever is making their four-legged family member sick.

Sometimes diarrhea is simply an upset stomach that will quickly pass. In these cases, diarrhea is not a cause for immediate alarm or antibiotic intervention. Other times, diarrhea is a clinical sign of an underlying illness that is much more serious.

We always recommend seeing your vet if your dog is not acting quite like themselves. Dogs notoriously hide any pain or discomfort. It’s your responsibility to know your dog’s day-to-day patterns in order to be able to quickly recognize any changes.

Furthermore, it also your responsibility to make sure your dog isn’t inadvertently passing an illness onto the neighborhood.

If your dog is having unexplainable bouts of diarrhea, it is important that they see a veterinarian. It is quite possible that they have Giardia.


Can you define Giardia in dogs?

What is Beaver Fever?

What are the signs of Giardia in dogs?

What can I do to prevent Giardia in my dog?

How is Giardia in dogs treated?


The Facts You Need to Know About Giardia in Dogs › Dogs › Dog Health

About the author

Chelsea Hunt-Rivera

Chelsea Rivera is a Dedicated Pet Parent who loves to create amazing content for pet owners and is helping change pet wellness as the Head of Content for