Giardiasis in Dogs & Cats: Causes, Symptoms, and Natural Treatments of Giardia in Dogs & Cats

Giardia, a single-celled parasite that often wreaks havoc in our cat and dogs’ digestive systems, is notorious for causing significant discomfort and diarrhea. While conventional treatments have been the go-to for many veterinarians, they can have limited results and a surge in natural treatments are changing the game.

What Is Giardia In Dogs & Cats

Giardiasis, the disease caused by Giardia duodenalis, is a common microscopic protozoal intestinal infection in dogs and cats. The protozoa thrives in feces-contaminated soil, food, and water. Giardia is a common cause of ‘traveler’s diarrhea’ in people worldwide. Giardia in dogs and cats can cause severe signs of disease and can greatly impact cat and dog’s gut health if they become infected.

How Is Giardia Transmitted To Dogs & Cats

A dog and cat becomes infected when it ingests the cystic form of giardia from the environment. Pets get infected by ingesting these contaminated materials in the soil, food and water. Two forms of the parasite exist:

  • Trophozoites: These are the active form of giardia that resides in the intestines of infected dogs and cats.  If there are sufficient amount of trophozoites in the intestinal tract, then clinical symptoms can occur due to the gastrointestinal damage.
  • Cysts: Trophozoites transform into cysts, which have a protective outer shell, allowing them to survive in the environment for months. These cysts are shed in the pet’s stool and can cause re-infection if ingested. Cysts are hardy and can survive for months in the environment.


The time it takes from from ingestion of the cysts, transformation and then passage of the cysts out of the body back into the environment through the feces is 5 to 12 days in dogs and 5 to 16 days in cats. These cysts are immediately able to infect another animal.

When giardia cysts are found in the stool of an asymptomatic animal (no diarrhea), this generally means that the giardia is a transient infection and is just passing through and an insignificant finding.  This does not require treatment, but unfortunately, many animals are receiving antibiotics unnecessarily, which can impact the microbiome in the gut long-term.

What Are Symptoms of Giardia In Dogs & Cats

When these microscopic protozoa, specifically trophozoite form, multiply and attach themselves to the gut lining in pets, they create inflammation.  The damage they create to the intestinal wall causes foul-smelling, loose, watery diarrhea.  The stool can range from mushy to watery and may contain mucus and sometimes blood. Vomiting can occur in some cats and dogs with giardia. These signs can persist for weeks and gradual weight loss can occur due to malabsorption from food not being properly digested.

Giardia in dogs and cats is not usually life-threatening, but it can create long-lasting damage in a pet’s gut lining, which can predispose them to food sensitivities and even allergies later on in life. Many pets can be asymptomatic carriers, but as long as their immune system and gut health stays strong, they are able to handle transient passages of the giardia protozoa.

How Is Giardia In Dogs & Cats Diagnosed

Many veterinarians will start with a fecal floatation test to look for the cysts under a microscopic.  However, the cysts can be intermittently shed and may not always appear under the microscope.  If your veterinarian suspects giardia in dogs and cats, a stool sample may be analyzed for Giardia-specific antigens (cell proteins) through a special snap test that can usually be run in the clinic.

If diarrhea continues after treatment, your veterinarian may need to recheck a stool sample to see whether your pet has been reinfected. Retesting for antigens is not recommended because Giardia antigens can remain present for up to 6 months after a giardia infection has been successfully treated, which may result in false-positives on a test and unnecessary further treatment.

Retesting for fecal cysts is ideal to determine if an infection has resolved, especially if your pet’s stool is back to normal and the symptoms have resolved.  A monthly fecal floatation test every month looking for cysts is ideal for 3 months since cysts are intermittent shedders and then after 6 months retesting for antigens to confirm that the infection has been resolved. If symptoms are still present, the infection may not have been fully resolved and/or another condition may be occurring. 

If your pet is still experiencing gut health issues after resolving giardia in dogs and cats, make sure to watch our free Better Gut Health Masterclass.

A “New” Contender For Treating Giardia In Dogs: Ayradia

A recent introduction to the realm of giardia treatments is Ayradia. This drug has become the first FDA-approved animal drug for treating Giardia duodenalis infections in dogs only. But is it genuinely novel? Well, not exactly. Ayradia is essentially Metronidazole in liquid form.

During its evaluation, seven animals underwent a study, and a field study was conducted to ascertain its efficacy. With giardiasis being a prevalent concern, this new treatment option is being keenly observed by the veterinary community, but unfortunately this release of an old drug may just simply mean more pets will receive an outdated treatment that comes with many resistance issues and possible side effects.

If you’d like to learn more about this “new” medication, check out the FDA post:

In order to properly understand the studies, make sure to watch our YouTube video and read the Freedom of Information associated with the FDA post to learn more about Ayradia and giardia in dogs.

Conventional Treatments For Giardia In Dogs & Cats

Metronidazole has been the traditional choice for many vets. Given at a dosage of 15-25mg/kg every 12-24 hours for a week, it often requires a recheck after two weeks. If the pet is still shedding cysts, other treatments like Fenbendazole or Ronidazole may be combined or used as alternatives. It’s crucial to be cautious since these drugs have known side effects, like neurological issues, tremors, and bone marrow concerns. Notably, Metronidazole-resistance in humans can reach a staggering 90%. This is just another reason why a true holistic approach and preventative care is important to keeping your pet’s gut health strong.

Natural Alternatives To Giardia In Dogs & Cats: A Holistic Approach

Beyond conventional medicine, there are several natural treatments that have shown promise and have less adverse effects on your pet’s gut health

Natural Remedies

1.Garlic: Garlic has properties that inhibit giardia growth along with other antibacterial properties.  It is NOT toxic to pets when used in the appropriate amounts. This study that continues to be recirculated amongst my veterinary colleagues shows that over 5 grams/kg of body weight of garlic was given by a gastric tube to dogs over 7 days and then some blood value changes occurred, but none of the dogs actually exhibited issues at these extremely high doses.  Keep in mind that the “new” drug Ayradia also showed dogs had seizures when 10x the recommended dosage was given. Of course, we have adverse effects when we give abnormally high dosages that would never be accepted naturally by an animal in real life.  Here’s a study showcasing garlic’s powers as an anti-giardia remedy.

Here are the safe and effective garlic doses to use for giardia in dogs and cats:

  • ¼ clove for cats once daily
  • ¼ clove for dogs up to 10 lbs 3 times daily
  • ½ clove for dogs 11-20 lbs 3 times daily
  • 1 clove for dogs 21- 50 lbs 3 times daily
  • 1.5 cloves for dogs 51-100 lbs 3 times daily
  • 2 cloves for dogs over 100 lbs 3 times daily

2. Quercetin: This natural compound helps heal the gut and reduce histamine resulting from villi destruction from the giardia trophozoites. Quercetin is a plant-derived flavonoid found naturally in many fruits and vegetables, such as kale, green tea, blueberries, and broccoli. It’s more famous for its use for allergies as nature’s benadryl, but it also helps heal leaky gut and seal the tight junctions while also reducing histamine.

A safe dosing guideline for quercetin is 5-10 mg per pound of body weight, which can be given twice a day.

For example, a 75-pound dog will take about 500mg of quercetin twice a day by mouth.

3. Berberine: Berberine is an alkaloid from the medicinal plant, Berberis aristata. Goldenseal and coptis are other common plants that are high in berberine content. Much of berberine’s effectiveness is undoubtedly due to a combination of its direct antimicrobial activity, inhibition of microbial attachment to mucous membranes, and blocking of the action of toxins produced by several pathogenic bacteria. There are numerous studies that have showed that Berberine can be more effective than antimicrobials.

Thorne Berberine caps can be given to dogs and cats based on their weight at 10mg/kg once daily for dogs or 5mg/kg/day for cats.

4. Probiotics & Fiber: They play a vital role in maintaining a healthy gut balance by feeding the good bacteria and outcompeting the giardia trophozoites to keep them from attaching to the gut lining.  Beneficial bacteria and fiber also help support a healthy gut microbiome.

  • Standard Process Gastro-Fiber – This plant-based whole food fiber supplement encourages a healthy intestinal environment to support a normal flora while also maintaining a healthy GI pH to support the microbiome and ecosystem present. Standard Process Gastro-Fiber Supplement
  • Dosing For Gastro-Fiber: 1-20lbs: Give 1 capsule twice a day
    21-50lbs: Give 3 capsules daily
    51lbs+: Give 2 capsules twice a day
  • Standard Process ProSynbiotic – A probiotic blend to help with microbial support which is a synergistic blend of 4 probiotic microbes and a prebiotic fiber to support overall intestinal health. Studies have shown that using probiotics, like Lactobacillus and Saccharomyces, can help reduce the time of gastrointestinal symptoms and help repair the damage caused by giardia.
  • Dosing for ProSynbiotic: 1-20lbs: Give 1/2 capsule per day
    21-50lbs: Give 1 capsule daily
    51lbs+: Give 1 capsules twice a day
  • ProSynbiotic Supplement

5. Oregano: Oregano is an herb that contains powerful and effective anti-giardia compounds that help inhibit attachment of the trophozoites of giardia in dogs and cats GI lining.  Studies have shown that the plant compounds can instigate cellular death in the giardia organism.

  • Dosing when using the Designs for Health Oil of Oregano Capsule:
  • • Cats: 1 drop from capsule twice daily in the meal
    • Dogs up to 10 lbs 4 drops 2 times daily
    • Dogs 11-20 lbs 4 drops 3 times daily
    • Dogs 21- 50 lbs 1 capsule twice daily
    • Dogs 51-100 lbs 2 capsules twice daily
    • Dogs over 100 lbs 2 capsules 3 times daily

6. Standard Process Canine Enteric SupportThis product uses whole foods and glandular support, like l-glutamine, mushrooms, licorice and bile salts, to help support a healthy gut environment.  Giardia in dogs can create a lot of inflammation and uses whole foods can help heal the inflammation faster.  Follow the dosing guidelines on the box for your pet’s body weight.

Canine Enteric Support Supplement

After 14 days of any treatment, it’s essential to recheck fecal float for cysts and follow up as necessary. Consistent monitoring ensures the treatment is effective and the pet remains healthy.

Due to the effects giardia can have on dog and cats’ gut health, there are functional gut health tests that can be done to see the impact on the microbiome, the function of the gut ecosystem and the impact on the gut lining from handling an infectious microorganism.

  • Innovative Pet Labs – This company offers many different gut health test for dogs and cats that help pet owners take a proactive approach to making sure that the damage has actually been repaired. Use code NaturalPet25 for 25% off your gut health tests!
  • Animal Biome – This company offers a stool microbiome test to make sure that there is enough diversity of the microbes and that there is not an overgrowth of E. coli or Clostridium present that could’ve allowed the giardia to colonize the gut in the first place.

In Conclusion

Giardia, while a common concern for many pet parents, has a spectrum of treatments available. Whether you lean towards conventional drugs like Metronidazole or natural remedies like garlic and oregano, it’s crucial to stay informed and work closely with a trusted veterinarian to ensure the health and happiness of your furry friend.  Proactive testing and using a whole body approach to your pet’s care will help your pet’s regain and maintain optimal health after dealing with giardia in dogs and cats.

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  • Dashti N, Zarebavani M. Probiotics in the management of Giardia duodenalis: an update on potential mechanisms and outcomes. Naunyn Schmiedebergs Arch Pharmacol. 2021 Sep;394(9):1869-1878. doi: 10.1007/s00210-021-02124-z. Epub 2021 Jul 29. PMID: 34324017.
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  • Roy Upton,86 – Hydrastis canadensis (Goldenseal) and Other Berberine-Containing Botanicals, Editor(s): Joseph E. Pizzorno, Michael T. Murray, Textbook of Natural Medicine (Fifth Edition),Churchill Livingstone,
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*Disclaimer: This information is for educational purposes only and is not intended to replace the advice of your own veterinarian or doctor. The information contained in is strictly for educational purposes. Therefore, if you wish to apply ideas contained in, you are taking full responsibility for your actions. Please consult your veterinarian for medical advice for your own pets. Dr. Katie Woodley cannot answer specific questions about your pet’s medical issues or make medical recommendations for your pet without first establishing a veterinarian-client-patient relationship.  Links in the blog are typically affiliate links that let you help support us.

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