As a cat owner, there is nothing worse than when your kitty becomes ill. Giardia in cats can be challenging to identify, as the symptoms may be similar to those of other stomach or intestinal issues. However, with a thorough understanding of the causes and early recognition of potential symptoms, it is possible for you to treat an infection before it gets too severe. In this blog post, we will explore giardia in cats in depth so that you can have all of the information necessary to recognize and provide effective treatment if needed.

What is the lifecycle of giardia in cats?

The life cycle of giardia in cats is relatively simple but plays a crucial role in understanding how the parasite infects cats and other animals. Giardia is a single-celled, flagellated protozoan parasite that exists in two main forms: the motile trophozoite and the non-motile, infectious cyst.

Let's take a closer look at the various stages of the giardia life cycle in cats.

  1. Ingestion: The life cycle of giardia begins when a cat ingests infectious cysts from contaminated sources such as water, food, soil, or surfaces. The cysts can also be present on the fur or feet of infected animals, which can then be ingested during grooming or licking.
  2. Hatching: Once your cat has ingested the cysts, they travel to the small intestine. Here, the cysts "hatch" into a more active form of the parasite called trophozoites, triggered by the stomach's acidic environment and the presence of bile in the small intestine.
  3. Multiplication: The trophozoites attach themselves to the lining of your cat's small intestine, where they start to multiply by dividing into two new trophozoites. This multiplication can damage your cat's intestinal lining and cause the typical symptoms of a Giardia infection, such as diarrhea.
  4. Transformation: As the trophozoites multiply, some of them change back into the protective cyst form, a process known as encystation. These cysts can survive outside the host's body, waiting to infect another animal.
  5. Excretion: Your cat's body sheds the cysts through feces. Once outside, these cysts can contaminate water sources, soil, surfaces, or other animals, starting the life cycle all over again and potentially infecting new hosts.

What are the symptoms of giardia in cats?

Many cats infected with giardia may not show any symptoms or may have mild symptoms that go away on their own. However, diarrhea is the most common sign of giardia in cats. This diarrhea can take different forms, such as acute (sudden and severe) or chronic (long-lasting) diarrhea.

Despite diarrhea, many cats with giardia continue to eat well and maintain their normal energy levels, although they may experience some abdominal discomfort. In more severe cases, cats may lose their appetite, become dehydrated, lose weight, and become lethargic.

The severity of the symptoms can be worse in cats that have other gastrointestinal parasites, other health conditions like inflammatory bowel disease or are in a compromised state. If you suspect your cat might have giardia, it's essential to consult your veterinarian for proper diagnosis and treatment.

How is giardia diagnosed in cats?

The diagnosis of giardia in cats is typically made through a combination of physical examination and laboratory testing. The most common tests used to diagnose giardia in cats are fecal examinations, either directly under a microscope or with an enzyme-linked immunosorbent assay (ELISA) test. The ELISA test is more accurate than traditional fecal floatation testing and is currently the diagnostic test of choice for symptomatic cats.

How is giardia treated in cats?

The primary goal of treating giardia in cats is to alleviate the clinical symptoms. However, completely eliminating the infection can be challenging, so achieving a full cure is often considered a secondary objective. The difficulty in eradicating giardia can be attributed to the resistance of some giardia species strains to treatment. As a result, it may be necessary to try multiple medications or treatment attempts to successfully cure the infection.

Common medications that may be used to treat giardia in cats include:

  • Fenbendazole
  • Metronidazole
  • Albendazole
  • Febantel

In cases where giardia infections do not cause symptoms, treatment might not be necessary. Even though otherwise healthy animals can shed the parasite, there is limited evidence to suggest that shedding directly leads to disease transmission. However, treating asymptomatic cats could be recommended in certain situations, especially if there is a high risk of transmission to humans, such as when an immunocompromised person lives in the household.

Additionally, feeding your cat a low-residue, highly-digestible diet can be beneficial in helping to firm up their stools. Including fibre in their diet may also improve their condition by reducing bacterial overgrowth and potentially preventing the parasite from attaching to the intestinal lining.


In conclusion, giardia in cats is a relatively common parasite that can cause symptoms such as diarrhea, loss of appetite, weight loss, dehydration and lethargy. Diagnosis is typically made through physical examination and laboratory testing while treatments include medications like fenbendazole, metronidazole or albendazole. Additionally, feeding your cat a low-residue diet high in digestible fibre may help firm up their stools and reduce bacterial overgrowth which could potentially prevent the attachment of parasites to the intestinal lining. With proper care and attention from pet owners, giardia infections in cats can be successfully managed for long-term health benefits. Please contact your veterinarian if you have any questions about giardia in cats.