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Giardia in Dogs

Giardia in Dogs: What It Is and How Is It Treated

Giardia in dogs is an illness caused by a parasite. Your dog can unknowingly ingest the parasite, so it’ll be hard to tell that he’s got the giardia parasite until signs and symptoms show up. In this case, you must arm yourself with everything there is to know about giardia!

This article introduces you to what giardia is and what disease it causes in dogs. You’ll also learn giardiasis signs and symptoms, how vets diagnose the condition, and treatment options your dog may take. Finally, we’ll give you tips to care for your dog and prevent an encounter with giardia in the future. So, delve right into this complete guide to understanding and treating giardia in dogs!

Meet Giardia, the Parasite Behind Giardiasis

What is guardia

Giardia is a microscopic protozoan parasite that can cause diarrheal disturbances in dogs, cats, birds, mammals, and humans. They are completely different from bacteria, viruses, fungi, and worms. The organism is also known as Giardia duodenalis, Giardia Intestinalis, and Giardia lamblia. Giardia resembles a pear in shape, with whip-like structures on its body called flagella.

Giardia duodenalis has seven known genotypes from A to G. These assemblages are known to infect certain hosts:

  • A and B – Humans
  • C and D – Dogs
  • E – Livestock
  • F – Cats
  • G – Rodents

As such, the parasite’s various genotypes prefer particular groups of animals and humans as hosts. However, the possibility of zoonotic infection (disease transmission from animal to human) is still there. Cross-species infection is rare but also possible, especially for households with multiple pets at home.

Unlike other parasites, Giardia survives and thrives in cool moist environments for several weeks. It can live in the soil for up to 7 weeks during winter (1 week during normal breezy days). Meanwhile, the parasite lives for 1-3 months in waters with a temperature below 10°C/ 50°F. These waters may include refrigerated water or lakes/ponds/puddles during winter.

Giardia’s Life Cycle

Giardia’s Life Cycle

The life cycle of giardia is among the simplest of all parasites. It starts with the host animal ingesting the cyst form of giardia. Cysts are commonly seen in food or water contaminated with feces.  When these cysts reach the intestines, they divide and release trophozoites (active feeding form of giardia) through a process called excystation

Now, as the trophozoites are swept down further inside the intestines, they produce infectious cysts through encystation. These cysts pass out the body through the feces, with the potential to infect other host animals and humans again.

What is Giardia in Dogs?

What is Giardia in Dogs

Dogs that ingest giardia often experience a condition called giardiasis. It’s characterized by sudden watery diarrhea that can last for a few days. Since the parasite clings to the intestinal walls, the affected dog finds it hard to absorb water, electrolytes, and nutrients from his food intake. This can lead to other problems such as weight loss and sluggishness.

Symptoms of giardia in dogs do not always present readily. Often, symptoms manifest after 1-3 weeks from the ingestion of contaminated food or water. Also, giardia may unknowingly be spread by your dog through his feces even if he doesn’t show any symptoms. It takes 5-12 days for ingested giardia cysts to pass outside a dog’s body through feces.

Dogs susceptible to giardiasis include puppies, older dogs, and those with compromised immune systems. Animals in kennels, shelters, and breeding facilities are also likely to be infected with the Giardia duodenalis parasite.

How Do Dogs Get Giardia?

How Do Dogs Get Giardia?

Dogs easily get giardia because they love putting things in their mouths. They tend to lick their butts, bite sticks, roll around soil, drink from puddles, chew grass, and even eat their poop! Giardia can quickly get in their bodies and live inside their intestines, unfortunately causing problems with their digestion, nutrition, and elimination.

Read more about why dogs eat grass and poop here:

The most common way dogs get giardiasis is through ingesting contaminated water. Dogs may drink water soiled by feces from other animals. Contaminated water is often seen outdoors, so your dog may potentially get giardia after a day outdoors or from a hike in the woods.

Signs and Symptoms of Giardia in Dogs

Signs and Symptoms of Giardia in Dogs

Giardiasis in dogs isn’t detectable right away. As we mentioned earlier, symptoms may only show up 1-3 weeks after your dog has ingested the giardia cysts through contaminated food or drink. The average time when symptoms appear ranges from 5-10 days after parasite ingestion.

Suspect giardiasis if your dog shows any of these symptoms:

  • Sudden onset of diarrhea
  • Unusually soft and light-colored stool
  • Bloating and gas
  • Swollen tummy
  • Indigestion
  • Refusal to eat
  • Vomiting
  • Weight loss
  • Dehydration
  • Poor appearance of coat and skin

Dogs with giardiasis may experience either intermittent or long-term diarrhea. Fats, blood, or mucus may also be present in the stool. Puppies are especially susceptible to such kinds of diarrheal stools.

There are also giardiasis cases wherein dogs never showed any signs and symptoms. If your dog didn’t experience the symptoms above but you feel there’s something off with him or his digestion, take him to the vet to be on the safe side. Have your vet evaluate him especially if you’ve come from an outdoor trip with your dog.

Giardiasis Diagnosis in Dogs

Giardiasis Diagnosis in Dogs

Your vet may run several tests to confirm the presence of Giardia in your dog’s feces. And with that, two or more kinds of tests may be required to completely rule out other illnesses and confirm giardiasis. No two tests are the same, and each test has different levels of accuracy as analyzed in this study.

Diagnostic tests for giardiasis in dogs include the following:

1. Fecal examination

The vet will take samples of your dog’s fresh fecal matter and examine it using either of these three methods:

  • Direct fecal smears
  • Saline wet mount
  • Fecal floatation by centrifugation

Your vet may require several consecutive samples since the giardia cysts are intermittently shed. One fecal test doesn’t guarantee that the cysts will immediately be seen and identified. Typically, vets may take three samples from your dog over 5-7 days.

2. Giardia ELISA Test

ELISA (enzyme-linked immunosorbent assay) test is a diagnostic exam that looks for a specific Giardia protein/antigen in the dog’s fecal matter. Your dog’s veterinarian may resort to this diagnostic exam in conjunction with fecal exams or if false-negative results arise from them. Qualitative ELISA and SNAP Giardia tests are the most common ones used.

3. Immunofluorescence Assay (IFA)

Fecal IFA is a serological test considered as the gold standard in diagnosing giardia in dogs. In IFA, Giardia antigens are detected by deploying fluorescently-labeled antibodies. The presence of antigens confirms that Giardia duodenalis is indeed on the fecal matter.

4. Polymerase Chain Reaction (PCR)

PCR is another alternative diagnostic test to detect giardiasis in dogs. The exam is done by checking the feces for Giardia’s DNA sequence. It’s a fast and sensitive way to detect giardiasis, although IFA is still generally more accurate and cost-effective.

Treatment Options for Giardia in Dogs

Treatment Options for Giardia in Dogs

Healthy and asymptomatic Giardia-positive dogs often heal on their own and do not require any kind of treatment. However, it’s a good idea to have your asymptomatic dog treated when:

  • You have other pets at home
  • You have family members or pets with weakened immune systems
  • You have kids and/or elderlies inside your home
  • Your dog has too many cysts even if he’s asymptomatic

Here’s the catch, though: There’s no specific medication for Giardia. However, veterinarians often prescribe medications to help kill the parasite inside the dog’s body. These off-label medications include:

  • Fenbendazole – Originally used as a dog deworming agent
  • Metronidazole – An antibiotic used in giardiasis treatment for both dogs and humans

Metronidazole has been the gold standard in treating giardiasis in dogs. However, Giardia parasite tends to become resistant to the drug. Because of this, fenbendazole use is becoming more popular today. Fenbendazole also has fewer side effects than metronidazole, and it’s safe to use for pregnant or lactating dogs.

Some vets give combinations of these two drugs to dogs with severe diarrhea unresponsive to supportive treatment. The antibiotic course runs for three to ten days.

Other possible antibiotics your vet may prescribe include the following:

  • Albendazole
  • A combination of febantel, praziquantel, and pyrantel

Your vet will inform you about how to give supportive care to your dog while he’s on antibiotics. Meanwhile, repeat fecal tests will be taken during the treatment course to check if the medications are effective at eliminating the Giardiasis parasites. Your dog will also be re-tested around 2-4 weeks after treatment completion to see if there’s no more trace of the parasites in his body.

Caring for Dogs with Giardiasis

Caring for Dogs with Giardiasis

Apart from the medications, you’ll need to give your dog supportive care to get him back on his feet. As you may already know, a dog with giardiasis may feel weak, have a poor appetite, and may experience weight loss and dehydration due to constant diarrhea. You can help your dog combat all these by doing the following:

1. Keep your dog well-nourished and hydrated.

Bring back your dog’s energy by giving him easily-digestible foods. Also, give him clean water to drink. Food that’s easy on the tummy will help your dog regain his strength and will replenish the nutrients and electrolytes lost during his diarrheal bouts. Keep his food and water bowls nearby and clean them after each use.

2. Bathe your dog regularly.

Promptly clean up your dog every time he moves his bowels. Give your dog a nice bath with pet shampoo every day as well. This ensures that all the Giardia cysts he sheds from his feces are thoroughly removed from his skin and coat.

3. Clean and disinfect the environment frequently.

Disinfect all potentially contaminated items as long as your pet is sick and under treatment. This includes linens, toys, water and food bowls, towels, floors, pet beddings, furniture, and other surfaces your dog has had contact with. Clean them every day as much as possible.

For cleaning, you may use regular soap, detergent, and carpet cleaning agents. Meanwhile, here’s what you need to use for disinfection:

  • Hard surfaces – Quaternary ammonium compound products (QATS) or ¾ cup of bleach mixed with a gallon of water
  • Carpets – QATS and steam-cleaning the carpeted area for a minute (100°C/212°F) or 5 minutes (70°C/158°F)
  • Linen, beddings, and cloth toys – Washing as usual in the washing machine, then either heat-dried on the highest setting for 30 minutes or air-dried under direct sunlight
  • Dishwasher-safe items like toys and water/food bowls – Disinfect items in a dishwasher with a final rinse or dry cycle with settings greater than the following:
  • 162°F/72°C for 1 minute
  • 122°F/50°C for 5 minutes
  • 113°F/45°C for 20 minutes

Always use gloves when cleaning and disinfecting the environment and your dog’s things.

4. Pick up your dog’s stool right away.

If your dog is outdoors or in your yard, promptly remove his feces to avoid infecting the environment. Wear gloves, remove the stool, and place it in a secured plastic bag before throwing it away. Also, eliminate any standing water sources as much as possible. This includes unused fountains, puddles, and containers with water.

5. Limit your dog’s access to outdoor spaces while he’s still in treatment.

If you have several pets at home, limit your dog’s access to common outdoor spaces. Also, don’t allow younger pets to enter common outdoor spaces while your infected dog is still under treatment. Keep in mind that dogs and other pets can quickly be infected or reinfected despite your best efforts to clean the environment.

Preventing Giardiasis in the Future

Preventing Giardiasis in the Future

Here are some ways to prevent your dog from contracting Giardia parasites in the future:

1. Ensure a steady supply of clean water.

Make sure your dog always has access to clean water wherever he is. Consider bringing some water from home if you’re headed outdoors or into the woods with your dog. That way, your dog won’t have to drink water that’s potentially untreated or contaminated with fecal matter from other animals.

2. Promptly clean up your dog’s stool in your yard or outdoors.

Remove your dog’s feces from the environment as soon as possible. Wear gloves and pick up his stool right away so that it cannot infect your yard or the outdoors. This applies even if your dog is already cleared from giardiasis.

3. Train your dog to stop eating poop.

If your dog is eating poop, train him to prevent this behavior. You can help your dog overcome this troubling behavior through a comprehensive behavior modification plan which includes obedience training and remote-device correction for older dogs [1]. Clicker training is also an effective way to train your dog for obedience [2].

The Wrap-Up

Giardia in dogs is a condition that results in diarrhea and intestinal disturbance. It can be tricky to diagnose the condition, but once it’s confirmed, you and your vet can give medications and supportive care to eliminate the parasites and improve your dog’s digestive health. Cleaning the environment, giving your dog clean sources of water and food, and training your dog to remove disturbing poop-eating behavior are some of the ways you can prevent giardiasis in the future.


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  5. Center for Disease Control and Prevention. Giardia & Pets. CDC Org.
  6. Center for Disease Control and Prevention. (2015). Pathogen & Environment. CDC Org.
  7. Medscape. (2018). What is the life cycle of Giardia during transmission of giardiasis?.
  8. Einarsson, E., Svärd, S.G. Encystation of Giardia intestinalis—a Journey from the Duodenum to the Colon. Curr Trop Med Rep 2, 101–109 (2015).
  11. M. Rishniw, J. Liotta, M. Bellosa, D. Bowman, and K.W. Simpson. (2010). Comparison of 4 Giardia Diagnostic Tests in Diagnosis of Naturally Acquired Canine Chronic Subclinical Giardiasis. Online Library Wiley.
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  13. Stregowski J., (2020). Why Dogs Eat Poop and How to Stop Them. The Spruce Pets.
  14. Evason M., Stul J., Canine Giardiasis.
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