Is your pet exhibiting soft stools or bouts of diarrhea, and seems a little off? The chances are it's infected with Giardia, a common parasite that affects pets.

It's likely they drank water from a puddle or ate something suspicious outdoors, but don't brush it off as a simple stomach upset, because it might indicate a chronic infection.

Giardia is far more stubborn and widespread than most pet owners realize. It can spread quickly, survive harsh environments, and cause long-term digestive problems if left untreated.

According to the CAPC (Companion Animal Parasite Council) report, up to 12% cats and over 15% of dogs in the U.S. carry Giardia at any given time, sometimes with no symptoms at all.

Nevertheless, Giardia is completely treatable and preventable with timely veterinary intervention, starting with diagnosing the symptoms and administering the proper medication and practicing smart hygiene habits like giving your pet clean drinking water, washing food bowls daily, cleaning poop promptly, feeding fiber-rich food, and keeping them from drinking puddle water.

In this article, you will learn what Giardia really is, how it spreads, the telltale symptoms, how to diagnose and treat it, and, most importantly, how to prevent it from coming back.

What is Giardia Parasite?

Giardia is a microscopic parasite, Giardia duodenalis, that lives in contaminated water sources. It is a protozoan, a single-celled organism that’s highly adept at survival; not a worm, a bacterium, or a virus.

However, unlike bacteria or viruses, Giardia does not invade the body’s tissues; it feeds on nutrients in the small intestine and disrupts digestion. Their presence in the host intestine can cause diarrhea, though some hosts are symptom-free carriers.

Giardia has two forms: the trophozoite and the cyst. Trophozoite is the parasitic stage that lives within the host, swimming around and attaching with its suction cup. The cyst, however, is the form that lives out in the environment at the contagious stage.

1. How Does Giardia Spread

Contaminated water is the most common way, but infected animals can also shed trophozoites and cysts in their fresh feces.

The main culprit is Giardia cysts, the parasite’s hard-shelled, infectious form that can survive potentially for months in moist, cool environments like soil, water bowls, or puddles.

Animals often get infected by:

• Drinking contaminated water (puddles, lakes, or shared bowls at dog parks)

• Licking contaminated surfaces like fur, paws, toys, or bedding

• Sniffing cysts from contaminated ground

• Grooming another infected animal

• Contact with contaminated feces or moist soil

Once inside the body, trophozoites can live in different parts of the intestine depending on the host species, but they can move to new areas based on the host’s diet and turn into an infectious cyst.

When the host has diarrhea, both trophozoites and cysts are released, and either form can appear in fresh stool.

When Giardia cysts appear in the stool of a healthy adult dog without diarrhea, they are usually considered a harmless, transient finding. But in puppies and weak or sick adult dogs, the infection can cause severe, watery diarrhea that may become life-threatening if not treated.

After infection, Giardia usually appears in the stool within 5–12 days in dogs and 5–16 days in cats, and these animals can immediately infect other animals.

Giardiasis often spreads in crowded places like kennels, pet stores, and animal shelters. And since Giardia cysts are microscopic and resistant to most disinfectants, they can easily go unnoticed. That's why even the cleanest homes and the healthiest pets can be at risk.

2. Why Giardia Is More Common Than You Think

According to the CAPC, Giardia ranks among the top five intestinal parasites found in dogs and cats across the U.S. Warmer, wetter regions tend to have higher rates, but cases appear nationwide.

In addition, puppies and kittens are nearly twice as likely to be infected and to act as carriers compared to adults. Young animals have weaker immune systems and love to explore, lick, and chew everything they find.

Even more concerning, Giardia can affect humans, too, especially children or immunocompromised individuals. Although transmission from pets to people (zoonotic infection) is rare, it’s still possible.

That’s why managing Giardia isn’t just about pet health– it’s also about household safety.

3. The Hidden Cost of Ignoring Giardia

Many owners dismiss Giardia as a minor issue, especially when symptoms are mild. But long-term infection or frequent reinfection can have serious consequences, such as:

• Continual nutrient malabsorption leads to weight loss and poor coat quality in dogs and cats.

• Immune suppression makes your pet more vulnerable to other infections.

• Long-term intestinal damage can trigger inflammatory bowel disorders.

In severe cases, especially for puppies, kittens, or senior pets, Giardia can cause dehydration and even hospitalization.

Ignoring symptoms might save time in the short run, but it often leads to recurrent vet visits and higher costs later. Treating early is always cheaper, safer, and kinder.

Clinical Signs of Giardia in Pets

Recognizing the clinical signs is the first step, but you must also understand the frustrating irregularity of the symptoms.

Giardia symptoms can range from mild to severe, depending on the pet’s age, immune health, and parasite load. Some animals carry Giardia without showing any signs, while others develop noticeable digestive issues.

Common Symptoms in Dogs and Cats

• Intermittent or chronic diarrhea

• Foul-smelling feces

• Gas and bloating

• Weight loss despite eating normally

• Lethargy and dehydration

• Mucus in stool

• Occasional vomiting

• Unusual hair loss (Sometimes)

These subtle changes often indicate the body is struggling to absorb nutrients due to intestinal irritation.

Giardia doesn’t always cause constant diarrhea – it often comes and goes, which tricks many owners into thinking the problem has resolved when it hasn’t.

Diagnosing Giardia: Why A Single Stool Checkup Is Not Enough

If your vet suspects Giardia, they’ll ask for a fresh stool sample to run diagnostic tests. However, since Giardia cysts aren’t shed continuously, a single negative test doesn’t always rule out infection, and symptoms can generally overlap with other intestinal diseases.

So, veterinarians often use a combination of tests and clinical evaluation to confirm infection.

1. Fecal Examination (Microscopic Testing)

A lab technician examines a stool sample under a microscope for cysts or trophozoites. Because Giardia doesn’t shed in every bowel movement, your vet may ask for stool samples collected over three consecutive days, which increases the chance of catching the parasite in action.

It may show direct evidence of Giardia in your pet's stool, but a single test might miss the infection if cysts aren't being shed that day.

2. Fecal Flotation Test (Zinc Sulfate Centrifugation)

This test is a more refined version of the basic stool check. The vet mixes your pet's stool with a zinc sulfate solution to help cysts float to the surface for easier detection under the microscope. However, studies show that a single fecal float test can yield a false-negative rate exceeding 70% in infected animals.

It's a quick, affordable way to spot cysts, but it still depends on when your pet sheds the parasite.

3. ELISA test (Enzyme-Linked Immunosorbent Assay)

It is a lab-based antigen test that detects specific proteins from the Giardia parasite in your pet's stool. It does not rely on seeing the parasite itself, so it's more reliable if cysts are not visible under a microscope.

It's more accurate and can detect infections even when shedding is low.

4. SNAP Test (Rapid Antigen Test)

It is a quick in-clinic version of the ELISA test, often called the Giardia SNAP test. Your vet mixes a small stool sample with a special solution and places it on a test device for quick screening without the need for a full lab setup.

It's fast and, within minutes, provides an accurate answer right at the vet's office.

5. PCR (Polymerase Chain Reaction) Test

This DNA-based test detects Giardia genetic material in your pet's stool, becoming one of the most sensitive and precise ways to confirm infection, and it can even identify which strain of Giardia your pet has.

It helps diagnose challenging or recurring cases that other tests might miss.

6. Combination Testing (For Accuracy)

Since no single test catches Giardia every time, your vet may suggest a combination of tests. For example, a fecal flotation plus a SNAP or ELISA test. This approach yields the most accurate diagnosis, especially if your pet shows symptoms such as diarrhea, weight loss, or greasy stool, even if initial tests come back negative.

If your dog or cat has persistent diarrhea, weight loss, or a dull coat, don’t wait. Collect a fresh stool sample and take it to your vet.

Giardia is treatable, but catching it early not only helps your pet recover faster but also reduces the risk of household contamination.

Treatment: How to Get Rid of Giardia in Dogs and Cats

The challenge lies in eradicating both the parasite and its cysts from your pet’s environment.

When deciding whether to treat Giardia, consider factors such as contact with vulnerable or immunocompromised people or dogs, the dog’s lifestyle, and its previous treatment history.

1. Medications

Generally, in healthy dogs without symptoms and carrying a non-zoonotic Giardia strain, treatment is unnecessary. For pets that do show symptoms but have a non-zoonotic strain, a high-fiber diet with probiotics may be enough to manage the infection.

If medication is needed, the CAPC recommends the following options:

• Metronidazole oral suspension (25 mg/kg twice daily for 5 days) — FDA-approved for dogs.

• Fenbendazole (50 mg/kg once daily for 3 to 5 days) — effective at clearing Giardia infections and considered more effective than metronidazole based on research; it is approved for Giardia treatment in dogs in Europe.

• A combination of febantel, pyrantel pamoate, and praziquantel (DrontalPlus) — effective when given daily for 3 days at the dosage listed on the DrontalPlus label.

Do not fret! – Treatment typically lasts 5 to 10 days, depending on the severity. Follow-up fecal tests confirm whether the infection is clear.

Pro Tip: Never self-medicate your pet using leftover human prescriptions, online advice, or friendly suggestions. Incorrect dosages or drug types can cause toxicity and liver damage.

2. Nutrition and Gut Support During Recovery

Giardia damages the intestinal lining, reducing the body's ability to absorb nutrients. Therefore, even after the parasite is gone, your pet's gut may remain inflamed for a while, for which your dog or cat needs strong nutritional and gut support to heal their digestive system, restore balance to the microbiome, and support a faster, safer recovery.

• Provide easily digestible food: Feed bland, low-fat meals, such as boiled chicken with rice, or a vet-approved GI formula that reduces intestinal stress and improves nutrient absorption. Avoid rich, fatty, or heavily processed foods, as they can worsen diarrhea.

• Focus on hydration: Always provide clean, fresh water, and consider adding electrolyte solutions recommended by your vet to replace lost minerals due to diarrhea.

• Support the gut microbiome: Probiotics (like FortiFlora or Purin Pro Plan) help restore beneficial gut bacteria, strengthen the immune system, and prevent Giardia from returning. Prebiotics such as insulin or FOS (fructooligosaccharides) can also feed beneficial bacteria and promote a balanced gut.

• Ensure proper nutrition for healing: Choose lean protein sources like chicken, turkey, or white fish. Add soluble fiber, such as canned pumpkin or psyllium husk, to firm up stools, and small amounts of omega-3 fatty acids (from fish oil or flaxseed oil) to reduce inflammation and promote gut healing. Fiber helps flush out leftover cysts from the gut.

• Avoid unnecessary treats and dairy: Many pets become temporarily lactose-intolerant after a Giardia infection, so skip milk and cheese. Also, avoid sugary or artificial treats, which can upset the gut and slow recovery.

In short, your pet’s diet after Giardia should focus on gentle, digestible, and nourishing foods that rebuild the intestinal lining, restore hydration, and strengthen gut health.

3. Cleaning and Hygiene: Breaking the Reinfection Cycle

The hardest part of treating Giardia isn’t killing the parasite—it’s preventing reinfection. Cysts are incredibly hardy and can survive for weeks in the environment, which is why pets often reinfect themselves through contaminated surfaces.

To keep your dog or cat healthy and prevent reinfection, you must break the cycle by maintaining strict cleaning and hygiene practices.

Here’s how to keep your home Giardia-free:

1. Wash your pet regularly: Bathe your dog or cat after treatment begins, and repeat 2 to 3 days later to remove any cysts from fur. Use a gentle pet shampoo and rinse thoroughly, especially around the tail and paws, where contamination is most likely to occur. Dry them with clean towels and wash the towels right away.
2. Clean the living area daily: Disinfect floors, crates, litter boxes, toys, and food bowls using a bleach solution (1 cup bleach per gallon of water) or a vet-suggested disinfectant. Giardia cysts can cling to surfaces, so wipe and rinse thoroughly. Wash bedding, blankets, and toys in hot, soapy water and let them dry completely before reuse.
3. Pick up feces immediately: Always remove your pet’s feces as soon as possible—every time, without delay. Double-bag the waste and dispose of it properly. This single step drastically reduces the spread of cysts in your yard or home.
4. Maintain outdoor hygiene: If your pet uses the yard, spray or rinse contaminated areas where possible and prevent puddles from forming. Do not let your dog drink from outdoor bowls, puddles, or streams, as Giardia often spreads through contaminated water. Avoid shared water sources at parks or daycares.
5. Keep your pet’s paws clean: After walks (in wet or muddy areas) or potty breaks, wipe your pet’s paws with warm water or pet-safe wipes. This simple habit helps prevent cysts from being tracked back into your home.
6. Practice personal hygiene: Wash your hands well after handling your pet, cleaning up feces, or touching contaminated items. Giardia can occasionally pass to humans, so good hygiene protects everyone in the household.
7. Repeat deep cleaning during and after treatment: Continue disinfecting and washing regularly for at least a week after your vet confirms recovery. This ensures no dormant cysts survive to cause another infection.

Why Giardia Keeps Coming Back

Sometimes Giardia feels like a never-ending loop. You treat it, and it returns weeks later. This happens because cysts are resilient, and pets may reinfect themselves before their immune systems fully recover.

Here’s what to do if Giardia keeps recurring:

• Retreat under veterinary guidance: A second round of thorough examination and medication is sometimes necessary.

• Deep clean your home: Use deep-cleaning products like bleach or quaternary ammonium compounds on hard surfaces, and focus on carpets, crates, and areas where moisture lingers.

• Test for co-infections: Check for other parasites or gut issues that can weaken immunity.

• Improve diet quality: Fiber and nutrient-rich food help your pet resist future infections.

• Limit exposure: Keep your pet away from park-pools, communal water bowls, or kennels until cleared.

Additionally, some vets recommend rotating probiotics or using immune-boosting supplements for pets prone to reinfection.

Preventing Giardia: Smart Habits for Long-Term Health

You cannot control every puddle or mud patch your dog encounters, but you can significantly reduce the risk with a few habits.

1. Outdoor Safety

• Keep pets from drinking from natural water sources, eating grass, or sniffing other animals’ feces. Bring your own water bowl on hikes or park visits.

• For dogs, avoid off-leash areas that may not be well-maintained or cleaned. For cats, consider a secure outdoor enclosure or supervised outdoor time to reduce exposure.

• Avoid heavily used dog parks after rain, when contamination risk is highest.

• Do not let your pet interact with unfamiliar or ill animals at dog parks, kennels, or shelters.

• If your dog or cat attends daycare or training classes, make sure the facility follows strict hygiene and sanitation standards.

2. Uphold Home Hygiene

• Clean food and water bowls daily with hot, soapy water.

• Clean up feces promptly from your yard, litter box, or kennel, and sanitize quickly.

• To avoid cats from snooping here and there, scoop litter boxes, rinse empty utensils, and scrub toys.

• In multi-pet households, you must separate feeding and drinking areas to avoid cross-contamination.

• Wash your hands after handling pets, outdoor play, cleaning litter boxes, or picking up waste.

3. Maintain Proper Grooming Habits

• Provide regular baths as they help to remove Giardia cysts clinging to fur and paws.

• Wash all bedding and toys in hot water to prevent any transmission.

• Trim long hair around the rear area to make cleaning easier and reduce the chance of reinfection.

4. Strengthen Your Pet’s Immunity Through Diet

• Feed a balanced, high-quality diet rich in protein, fiber, and essential nutrients.

• Include probiotics or probiotic-rich foods to support gut health and build resistance.

5. Routine Vet Checks

• Schedule yearly fecal tests, especially for multi-pet or outdoor households.

• Deworm and test puppies and kittens regularly since early infections can stunt growth.

• Always follow your vet’s guidance to prevent contamination plus zoonotic infection.

Preventing Giardia is all about consistency – clean water, good hygiene, and regular veterinary care. These small steps build a safer, healthier environment for both your pets and your family.

Can You Catch Giardia from Your Pet?

This is one of the biggest worries among pet owners. The truth is, although pet-to-people transmission is rare, some strains of Giardia are zoonotic (according to the CDC), while others are species-specific.

For example:

• Assemblages A and B of Giardia duodenalis can infect humans and animals.

• Assemblages C and D affect only dogs.

• Assemblage F affects cats only.

Human infection usually happens through contaminated water or poor hygiene, not direct contact with pets.

Still, if your pet has Giardia:

• Wash your hands after handling feces or cleaning litter boxes.

• Avoid letting pets lick your face or mouth.

• Disinfect shared surfaces regularly.

If someone in your home experiences diarrhea after a pet’s diagnosis, contact a healthcare provider for a stool test.

Key Takeaways

CATEGORY	DOGS	CATS
Causes	Drinking or licking contaminated water (puddles, streams, or dirty bowls) Ingesting feces or soil containing Giardia cysts Contact with infected animals or contaminated surfaces	Drinking contaminated water or grooming after contact with feces Living in a crowded or unclean environment (shelters, multiple homes) Exposure to infected litter boxes or outdoor areas
Symptoms	Watery, foul-smelling diarrhea Mucus in stool Weight loss despite normal appetite Lethargy and dehydration Occasional vomiting or soft stools	Intermittent or chronic diarrhea Greasy or soft stool with a strong odor Weight loss and poor coat condition Fatigue and dehydration
Treatment	Medications: Metronidazole (25 mg/kg BID for 5 days) or Fenbendazole (50 mg/kg SID for 3-5 days) Combination drugs: Febantel, Pyrantel Pamoate, and Praziquantel (DrontalPlus) for 3 days Diet: High-fiber, easily digestible food Gut support: Probiotics and hydration	Medications: Metronidazole or Fenbendazole (as prescribed) Diet: Bland, digestible meals to support gut healing Gut Support: Probiotics to restore healthy bacteria Hydration: Fresh water and electrolyte support
Prevention	Provide clean, filtered drinking water Pick up feces immediately Disinfect bowls, bedding, and play areas regularly Bathe after swimming or muddy play Avoid letting dogs drink from puddles Regular vet checkups and stool testing Supervise outdoor activity to avoid contaminated water and feces	Keep litter boxes clean and disinfected Provide only clean, fresh water Avoid contact with infected cats Wash your hands after cleaning litter Maintain indoor hygiene Regular vet checkups and stool testing Supervised outdoor time or use of enclosed cat runs

Conclusion

Giardia in dogs and cats is easy to underestimate – but it’s a persistent, contagious parasite that thrives in everyday environments and quietly undermines your pet’s health.

As a responsible pet owner, your best defense is awareness and action: watch for symptoms, get prompt veterinary testing, follow treatment carefully, and maintain a clean environment.

For any pet medical treatment, daycare and veterinary services, consult our experts at Urban Pet Hospital and Resort.