What Is Giardia in Cats?

Medically Reviewed by Amy Flowers, DVM on October 23, 2022
4 min read

What is Giardia in cats? Giardia is a parasite that can affect cats, humans, and other animals. Cats are particularly susceptible to many gastrointestinal (GI) parasites that affect different body parts and cause a variety of symptoms. 

Giardia, for example, causes an infection known as giardiasis, which causes problems with the digestive system. Unlike other parasites, Giardia is not a worm, bacteria, or virus. These parasites are made up of one cell and use a tail-like extension to move around. 

While giardiasis isn’t as common as other parasitic infections such as those of hookworm and roundworm, typically occurring in less than 5% of cats, it can be more prevalent in different environments. It commonly affects kittens and cats with weakened immune systems or other illnesses. 

To protect their pet, cat owners should understand what giardia is, how it’s contracted, its symptoms, and how it’s diagnosed and treated.

Giardia may be present in infected feces from humans and animals. Cats may contract giardiasis in several ways: 

  • Coming into contact with infected feces from another animal 
  • Rolling around or playing in contaminated soil 
  • Coming into contact with a contaminated surface, such as a litter box 
  • Consuming water from a contaminated creek, pond, or river

A cat recently infected with Giardia may not display symptoms immediately. They usually occur after 5 to 16 days. 

Symptoms of infection are primarily observed in the feces, though vomiting may also occur. Feces-related symptoms include: 

  • Diarrhea ranging in severity from acute to chronic
  • Stools that have a foul odor 
  • Stools that contain blood or mucous 

While a cat’s appetite may not be affected, gradual weight loss may occur. Additionally, a cat may become lethargic. Fortunately, Giardia infection is usually not fatal, although young kittens, older cats, and immunocompromised cats, such as cats with other diseases like Feline Immunodeficiency Virus (FIV) or Feline Leukemia Virus (FeLV), are at greater risk.

Diagnosing Giardia can be difficult. Certain cysts must be present in a cat’s stool for a diagnosis, and cysts are not passed consistently. Even when the cysts are passed, they are tiny, and it can be challenging to see them during routine fecal testing. Due to this, stool samples may need to be taken and tested several times. 

A fresh stool sample must be submitted for fecal tests: It cannot be older than 24 hours. Routine fecal examinations can be performed in veterinarian offices, but the veterinarian may also send the sample to a laboratory that uses a diagnostic method called centrifugal flotation, along with microscopic examination. Some veterinarian clinics also use enzyme-linked immunoassay (ELISA) technology to test fecal samples to determine if Giardia antigens are present.

Treatments for Giardia infections are categorized as at-home care, supportive care, and medicinal care. 

At-home care is the most common treatment option for infected cats since, in most cases, infections can be managed at home. At-home care includes giving your cat prescribed medications, putting them on a bland diet, and adding a probiotic to their food. Cats may also need to be bathed, shampooed, and rinsed thoroughly during treatment to help eliminate parasites and ensure that reinfection does not occur. 

Supportive care may include fluid therapy, especially in cats experiencing frequent vomiting and diarrhea. In severe cases, these symptoms can lead to your cat becoming dehydrated, and hospitalization with a treatment of intravenous (IV) fluids is needed. In more mild cases, a veterinarian may also be able to provide your cat with an injection of subcutaneous (SQ) fluids. 

Medicinal support usually involves oral medications such as metronidazole and fenbendazole. Still, while veterinarians often prescribe these two medications, they are not formally approved by the Food and Drug Administration (FDA) to be used in cats. These medications are typically used to treat dogs, and side effects can include vomiting and weight loss. 

Due to the bitterness of these drugs, they are often produced in a coated, tablet form. For cats, though, these tablets are typically split in half to provide a suitable dose, which may leave the bitter contents exposed. Metronidazole and fenbendazole may be used independently, but sometimes, using them together produces better results. These drugs also come in compounded forms, such as flavored liquid, so that the bitterness is masked.

All veterinarian instructions and recommendations must be followed while you are treating your cat. Fortunately, while Giardia can be hard to eliminate from an environment, an individual parasitic infection can typically be cured following a single course of treatment. During treatment, though, monitor your cat for symptoms like exhaustion, vomiting, diarrhea, and dehydration. 

Once treatment is finished, your veterinarian clinic will perform more fecal tests to ensure that the infection is gone.

Preventing giardiasis can be difficult since it can persist in an environment for months. Cats in kennels and those allowed to venture outside are more susceptible to contracting this infection. 

While Giardia can be difficult to remove from the environment altogether, there are specific preventive steps that you can take to reduce the chances of your cat becoming infected. These steps include: 

  • Removing feces from your yard and other outdoor areas that your cat may have access to 
  • Keeping a clean litter box 
  • Keeping your cat from going outside, especially if symptoms are present 
  • Regularly replace any water in bowls or fountains

There is no guarantee that an outdoor area will ever be Giardia-free, as soil can be contaminated with Giardia even if contaminated feces are removed. Some may consider using bleach or ammonium products to eliminate Giardia in soil and grass, but this won’t help. 

Instead, any cats with weaker immune systems (such as kittens) should be kept away from any outdoor spaces that may be contaminated.