Giardia in Cats

Facebook Icon Twitter Img Email Img Print Img

Giardia is an intestinal parasite that can affect both animals and humans. These tiny organisms live in the small intestine and can cause serious illness in infected cats. Infection among cats and dogs is common, with a widespread rate of 5–15%.

Giardia is not a worm, bacteria, or a virus: it is a simple one-celled parasitic species. It is more common in kittens and adult cats with compromised immune systems and can easily crop up in densely populated groups of cats in places like shelters, pet stores, etc.

Signs & Symptoms of Giardia in Cats

While many infected cats are asymptomatic, there are certain signs and symptoms that are indicative of giardia. (However, symptoms can also mimic other intestinal diseases, including IBD and cancer.)

The most common symptom of giardia is chronic, foul-smelling diarrhea, which can be continuous or intermittent. The stool is usually soft or even watery, pale, poorly formed, and may contain mucus.

Other signs of a giardia infection include:

  • Vomiting
  • Gradual weight loss
  • Being less active

In severe cases, cats may become dehydrated, lethargic, and exhibit poor body condition.

Not all cats infected with giardia become sick right away; some host the organism for several years and pass it on to other cats before they show any clinical signs. The disease is usually not life-threatening, but it can be more serious in kittens and older cats, or those with an already-compromised immune system.

Because giardia can be asymptomatic, felines that may be at risk (e.g., newly adopted kittens and cats) should be tested. Additionally, if your cat spends time outdoors, your vet may suggest annual testing.


Many cats with giardia are asymptomatic, sometimes for years. When the symptoms do present themselves, it’s important to see a veterinarian immediately. The most common symptom of giardia is chronic diarrhea. Kittens and older cats with other underlying conditions are more likely to become infected.

How Did My Cat Get Giardia?

The giardia organism undergoes two stages: a motile (swimming) stage and a cystic stage, with the latter being the primary means of transmission from host to host.

Giardia cysts are shed in the feces of an infected cat; the cysts are hardy and can survive several months in the environment, especially in water and damp environments. The cysts are transmitted to another host via ingestion, resulting in the host developing giardiasis (the name given to the infection caused by giardia).

Once the cyst enters the cat’s digestive system, it attaches itself to the intestinal wall to feed. This is when a variety of symptoms can begin to manifest.

After a cat ingests the cysts, they will pass in the cat’s feces anywhere between 5 and 16 days later. High humidity facilitates survival of the cysts in the open environment; transmission rates are highest in overcrowded spaces.


Giardiasis occurs when a cat ingests giardia cysts, usually via ingestion of infected feces or contaminated water. Overcrowded spaces like shelters can be hotspots for giardia transmission.

Diagnosing Giardia in Cats

In order to obtain an accurate diagnosis, the cat’s stool must be tested. The parasite will be visible in the fecal matter. However, it is not guaranteed that every stool sample will contain the parasite, so multiple samples may need to be tested for confirmation.

  • Fecal flotation test: The stool is placed in a small container and mixed together with a special solution. If present, giardia eggs will float to the top and stick to the cover slip, allowing for microscopic identification.
  • Fecal smear test: Usually performed in conjunction with the fecal flotation test, this diagnostic test helps identify possible causes of diarrhea.

In addition to fecal testing, some veterinarians also perform the SNAP test, which detects giardia antigens (proteins produced by the parasite) in fecal samples.


For an accurate diagnosis, the cat’s feces must be tested. In some cases, multiple stool samples may be necessary to confirm the disease.

Treating Your Cat for Giardia

The two most common drugs used to kill giardia are fenbendazole and metronidazole.

  • Fenbendazole: May reduce clinical signs and cyst shedding. Treatment is given orally for 3 to 5 days and is safe for pregnant cats.
  • Metronidazole: This medication appears to be more effective in cats than in dogs. Treatment is given for 5 to 7 days and is not safe for pregnant cats.

In certain cases, such as when a cat has refractory diarrhea (diarrhea that hasn’t responded to treatment), the two drugs can be given in combination. Your veterinarian will instruct you as to the best course of treatment.

The elimination of the disease can be difficult because of the resistance of some giardia strains. As a result, multiple drugs or more than one attempt at therapy may be needed.

Supportive therapy is also important. A low-residue, highly digestible diet is recommended until the cat’s stool hardens. Ensure your cat is drinking enough water: prolonged bouts of vomiting and diarrhea can bring on dehydration.

It is also important to bathe your cat thoroughly to ensure there are no parasites hiding in the fur. Cleaning your cat’s food and water dishes, removing feces from the litter box immediately, and keeping the litter box clean can help prevent the spread of giardia. (Just be sure to wear gloves to avoid coming down with giardia yourself!)

Is There a Cure for Giardia?

Yes. Giardia can be cured with medication. Metronidazole is the most common, but fenbendazole is another treatment veterinarians may prescribe, especially for cats that are pregnant or nursing.

Is Giardia Contagious for Humans or Other Pets?

Giardia is highly contagious between cats, and transmission is also possible between cats and dogs. The exact strain found in humans is not the same as the one found in cats, but it’s always better to play it safe and assume there is a possibility of transmission, even if it’s a very small one. So take the necessary precautions when handling an infected cat, as well as when you’re cleaning up the cat’s litter box, food and water bowls, and toys.

What Is the Cost for Treating Giardia?

If you suspect your cat is infected with giardia, there will be costs for both diagnosing and treating the infection. Those costs include:

  • Office veterinary visits: Your cat may need to be seen more than once, so it’s a good idea to factor follow-up visits into your cat’s medical expenses.
  • Testing: There is more than one test vets can perform, and each may carry a different cost.
  • Medication

As always, geographic location plays a role when it comes to cost. Larger cities generally have a higher cost of living, which translates to higher vet fees.


If your cat is diagnosed with giardia, there are medications to treat it. Supportive therapy is also important for recovery. Giardia is highly contagious, so precautionary measures should be taken to eliminate the risk of spreading the disease.

Recovery and Management of Giardia

Once a cat is infected, there is a 1 to 2 week incubation period. After that time, the body can start to react, so the sooner medication is administered, the more quickly recovery can begin. In most cases it takes 3 to 5 days for the parasites to be cleared from the stool and 5 to 7 days for symptoms to resolve. Even if it appears the symptoms have cleared midway through treatment, the entire prescription must be completed. Stopping before the entire course of medication is given could potentially cause resistance of the giardia parasite.

An infected cat should be retested after treatment ends—although it should be noted, even if the test results are negative at this point, reinfection can occur due to the fact giardia is extremely difficult to remove from the environment.


Once a cat is infected, symptoms can begin to show around a week or two later. Your vet will prescribe a treatment plan, which must be completed even if it appears that your cat has recovered midway through. Giardia is difficult to remove from the environment, making reinfection possible.

Preventing Giardia

Good hygiene is important when it comes to preventing the spread of giardia. Practices to follow include:

  • Thoroughly clean and disinfect litter boxes.
  • Wear gloves and wash your hands frequently when working with infected animals or feces.
  • Feces should be disposed of immediately.
  • Bathe all household pets following medical treatment to ensure there is no fecal residue within their fur.
  • Limit outdoor access and keep all household animals away from potentially contaminated water.

Is There a Vaccine for Giardia?

Currently, there is no vaccine for giardia.


Good at-home hygiene practices are the best way to prevent the spread of giardia. Keep cats indoors as much as possible, and away from possible sources of infection like contaminated water.

Facebook Icon Twitter Img Email Img Print Img

Related articles

Should I Spay or Neuter My Pet?

One of the most common complaints among dog owners is leash-pulling. Check out our…

Dog Skin Allergies: Atopic Dermatitis

Like humans, dogs are susceptible to developing allergies. Atopic dermatitis (or atopy)…

Parvo in Dogs

Parvo in dogs is a highly contagious and potentially deadly virus that…

Is flea & tick preventative needed all year?

For a lot of people—and their pets!—summer means spending time outdoors. That also means…

Diabetes in Dogs

Diabetes in dogs is an endocrine (hormonal) disorder that primarily affects middle-aged…

Lupus in Dogs

Systemic lupus erythematosus (SLE), commonly referred to as lupus, is a rare…

Kennel Cough in Dogs

Kennel cough, also known as canine infectious tracheobronchitis, is a highly contagious infection of…

Cat Pregnancy Facts

No matter how isolated your female cat is, if she has not…

Icon of a white arrow in a black circle Back to Learning center