Giardia in Dogs & Cats: Causes, Treatment, & More [Vet-Approved]

A dog crouching down to represent abdominal pain due to giardia in dogs

Pets are susceptible to a range of health issues, including infections that can affect their well-being. One such common culprit is Giardia in dogs and cats — a microscopic, waterborne protozoan parasite that can cause gastrointestinal upset, often catching both pets and their owners off guard.

While this single-celled organism might be tiny, its impact can be significant. From persistent diarrhea and vomiting to weight loss and lethargy, the effects of Giardia infection can be debilitating, especially in puppies, kittens, or pets with weakened immune systems.

In this Sploot Vets article, we talk about Giardia in cats and dogs, Giardia symptoms in dogs and cats, the importance of early Giardia detection, and more.

What’s in This Guide? 

What is Giardiasis or Giardia in Dogs & Cats

Giardia is a common microscopic intestinal parasite in dogs and cats. It can affect dogs and cats of any age or breed. The disease caused by Giardia is called ‘Giardiasis.’ In some cases, Giardia in dogs and cats may produce severe symptoms that require supportive therapy (i.e. SQ fluids). Senior dogs and cats, younger pets, and pets with compromised immune systems are more likely to show severe symptoms.

A puppy and kitten sitting side by side to represent young pets who are at risk for giardia in dogs

Cause of Giardiasis in Cats & Dogs

The scientific name of the protozoan species responsible for Giardiasis is Giardia duodenalis. G. duodenalis is further subdivided into ‘assemblages’,  labeled A through H. Dogs, cats, and humans can be infected with varying G. duodenalis assemblages:

  • Humans - G. duodenalis assemblages A & B
  • Dogs - G duodenalis assemblages A, C, & D
  • Cats - G. duodenalis assemblages A & F
Note: Veterinary clinics typically don’t narrow down the assemblage of G. duodenalis infecting a dog or cat — meaning G. duodenalis assemblage A, the assemblage that can infect pets AND humans, may OR may not be the cause. Thus, pet parents need to handle stool from an infected pet with precaution, alongside other good hygiene practices.

How Do Dogs & Cats Get Infected with Giardia?

Giardia in dogs and cats can be contracted via the following routes: 

  • Drinking contaminated water, which can come from rivers, lakes, puddles, stagnant water.
  • Being in contact with feces from an infected dog or cat (even in trace amounts);
  • Direct contact with contaminated objects;
  • Playing or resting on contaminated soil or surfaces (especially if the pet subsequently grooms or licks their fur and paws); and
Note: Giardia in infected soil or water can be viable (or capable of infecting a pet) for several months. 

Once inside a dog’s or cat’s body, Giardia either swims freely or attaches to the lining of a pet's intestines, disrupting nutrient absorption and leading to various uncomfortable symptoms.

Symptoms of Giardia in Dogs & Cats

The symptoms associated with Giardia in dogs and cats are the following:

  • Watery diarrhea;
  • Fatty stool (steatorrhea);
  • Abdominal gas;
  • Nausea/vomiting; and
  • Weight loss (especially common in chronic cases).

Some cases do NOT produce Giardia symptoms in dogs and cats. When a pet is found to have Giardia cysts in their stool during a routine fecal exam (typically part of regular wellness exams), the veterinarian will advise the pet parent if treatment for Giardia is needed.

When is Giardiasis in Pets Common?

Likely due to the parasite’s tendency to thrive in wet conditions, Giardia infections are found to be more common during rainy season than drier seasons. In many areas of the United States, the rainy season can encompass spring, summer, and fall.

Can Humans Get Giardia from Dogs and Cats?

When people get infected by Giardia, the most common sources are contaminated water sources or contaminated food. It is not as likely for humans to get giardia from dogs and cats, as long as good hygiene practices in place. 

Note: Pet owners are advised to be extra careful when handling the stool of a pet with suspected or diagnosed Giardia. For good measure, we recommend pet parents ALWAYS wash their hands after cleaning up any fecal matter (whether or not Giardia is suspected).  

Diagnosing Giardiasis in Dogs and Cats

Diagnosing Giardia in dogs and cats helps administer the best treatment as soon as possible — which puts a stop to incidents of watery diarrhea, which, in severe cases, can lead to dehydration, as well as other uncomfortable symptoms. 

Veterinarians employ different methods to diagnose a Giardia infection conclusively. In all of these tests, a fecal sample is used.

1. Direct Smear & Fecal Flotation for Giardia in Dogs & Cats

A direct smear of the fecal sample can be inspected under the microscope for Giardia cysts, which are microscopic hard shells containing the protozoa. To increase the chances of detecting Giardia cysts, veterinarians can use a technique called fecal flotation, which helps to isolate the Giardia cysts in a solution before doing a microscopic examination.  

2. Giardia Antigen Test for Dogs & Cats

Veterinarians can also use a giardia antigen test, an easier way of detecting Giardia, which detects Giardia antigens (proteins produced by G. duodenalis) in the dog’s or cat’s stool. 

Note: Only licensed veterinarians can diagnose Giardiasis in dogs and cats. Watery diarrhea, along with the other symptoms associated with Giardia, are not exclusive to Giardia — meaning that diagnosing based on symptoms is not conclusive. In addition, Giardia cysts, which signify the presence of Giardia in dogs and cats, are microscopic and require laboratory testing to be detected.
A vet using a microscope to detect giardiasis in dogs and cats by looking for giardia cysts

How to Treat Giardia in Dogs and Cats

Giardia in cats and dogs is treated with a prescribed antibiotic or dewormer; the duration of treatment varies per case. Medications are effective in resolving clinical signs of Giardia in dogs and cats, which is already a step forward in terms of health and well-being — a complete cure may be more challenging to achieve in some cases. 

Medication for Giardia in cats and dogs are not over-the-counter and will require a prescription from a licensed veterinarian. Veterinarians may also recommend a special diet for your pet while they are being treated for Giardiasis.

Most cases of Giardia can be treated at home after consulting a veterinarian and getting prescription medication. In some rare cases, severe symptoms may need hospitalization — this is usually the case for pets that are experiencing persistent diarrhea or vomiting which need to be managed with IV fluids. 

How to Prevent Giardia in Cats and Dogs

Though Giardia is an unseen threat, there are ways to help prevent this infection in dogs and cats. Check out the following Giardia prevention tips:

1. Ensure Clean Sources of Water

Avoid letting your pet drink from stagnant ponds, puddles, or other potentially contaminated water sources.

2. Proper Hygiene & Sanitation

Regularly clean and disinfect areas your dog or cat frequents or uses, such as their indoor living spaces, bedding, and feeding bowls. Doing so helps reduce the chances of contamination. As for outdoor environments, it is advisable to clean up a pet’s stool promptly —  whether in public spaces or in the yard. 

In addition, regular baths, cleaning up stool that gets stuck on a pet’s fur, and maintaining overall good grooming will help prevent Giardia cysts from clinging to a pet’s fur — and being subsequently ingested through licking).

Note: If your pet has just come home from a hike, swim, or exposure to the outdoors, we highly recommend giving them a bath afterwards. This will help remove Giardia cysts that may be on their fur or paws.

3. Regular Wellness Exams

Regular wellness exams for pets help detect any potential health issues, including Giardia in cats and dogs. An annual fecal exam, which can be included in your pet’s wellness exam, will help detect Giardia infections (even in asymptomatic dogs and cats). Early detection of this disease allows for early intervention.

A puppy getting a check up for giardia in dogs at Sploot Veterinary Clinic in Denver

How Long Does Giardia Last in Dogs and Cats? 

The duration of a Giardiasis infection in dogs and cats depends on their overall health condition and the promptness of effective treatment.

It’s also important to note that some pets may experience occasional flare-ups of Giardiasis — as these flare-ups stop and symptoms calm down temporarily, it gives a false impression that the protozoa parasite is gone for good. The best way to know if a pet is healed from Giardiasis is to consult a veterinarian.

Note: Reinfection can occur. Maintaining proper hygiene, practicing good grooming, and ensuring clean water sources for your pet will help in preventing reinfections.

How Serious is Giardia in Dogs and Cats?

The severity of symptoms of Giardiasis in dogs and cats depends on the pet’s overall health and age. Most pets do not experience severe symptoms. Typically, symptoms of Giardiasis in cats and dogs are more severe for puppies and kittens, elderly pets, and immunocompromised pets.

In addition, symptoms like diarrhea and vomiting are the easiest to detect — but some pets do not specifically experience these symptoms. Dogs and cats that only experience abdominal pain and gas due to Giardia will ‘appear’ to be asymptomatic. 

Final Thoughts About Giardiasis in Dogs and Cats

We hope you found this guide on Giardia in cats and dogs helpful! If you have specific questions about Giardia in pets or treatment options, we recommend reaching out to a veterinarian.

Sploot Veterinary Care is always here to help! We are a primary and urgent care veterinary clinic with multiple convenient locations and daily appointment availability

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