Giardia Infection in Pets

Updated: 6/17/24
Dog sniffing a pond


Giardia are single-celled organisms (protozoa) that can infect both people and pets, such as dogs, cats, and even chinchillas. Giardiasis (the disease caused by Giardia) can lead to diarrhea and occasionally blood in the stool and vomiting. Giardia live in the small intestine and have two lifecycle stages: the first is the cyst stage. These cysts are inactive and shed through feces. Shedding of cysts can last days or even weeks. Once the cysts are ingested by a host, they mature and multiply in the small intestine. These mature parasites go on to produce cysts and the cycle is repeated.

Infection occurs when an animal or person accidentally ingests the cysts shed through the feces of an infected animal. Oftentimes, Giardia is transmitted through contact with a contaminated object or environment, such as water or soil that have been tainted with feces. Different species of Giardia infect different animals. From what we know, species that infect dogs do not infect cats and vice versa. It is also quite rare for the dog species to infect humans.

Risk Factors

All pets are at risk for contracting Giardia if they are exposed to a contaminated environment, particularly those living in a shelter or near contaminated water. Other areas of increased risk include dog parks, breeding facilities, and kennels. The Giardia cysts can survive for weeks after being shed through feces, particularly in cool, moist environments.

Young puppies and kittens, senior pets, and immunocompromised pets are at risk for more severe cases of infection.


Common signs of giardiasis include:

  • Chronic diarrhea (intermittent or continuous)
  • Feces that is soft, pale, and appears to contain mucus
  • Vomiting
  • Weight loss
  • Increased intestinal gas or a bubbling sound in the stomach

While the above signs are indicators of giardiasis, it is not uncommon for dogs and cats infected with Giardia to show no clinical signs of infection whatsoever.


A Giardia infection is diagnosed through a stool sample. The cysts are visible under microscopic examination. However, as cysts are passed intermittently, your veterinarian may require several fecal samples collected over several days. The stool samples can be refrigerated overnight in a sealed container until you are able to give it to your veterinarian.

Besides microscopic examination, a specialized laboratory test called an enzyme linked immunosorbent assay (ELISA) may also be performed. This test is able to recognize a portion of the parasite and can detect an infection without cysts present in the stool sample.


If your pet is diagnosed with giardiasis, your veterinarian will prescribe medication to treat the diarrhea and eliminate the infection. The two commonly prescribed medications for dogs and cats are metronidazole and fenbendazole. Treatment can last anywhere from 3 to 8 days. Since pets can reinfect themselves though grooming, bathing your pet and placing them in an E-collar during and after treatment can decrease the risk of reinfection.

Your veterinarian may also recommend a bland diet that is easy for your pet to digest while they are recovering from the infection to be provided up until your pet’s stool returns to a normal consistency.

Pets that are asymptomatic may not require treatment. However, if your pet is showing any clinical signs of giardiasis, failure to treat the infection can lead to severe weight loss.


There are many steps pet owners can take to prevent the spread and contraction of Giardia in themselves and their pets.

Environmental Safety
Always make sure your pet has access to safe and clean drinking water. If you have a dog, use a portable water bowl while taking them on a walk and make sure they do not drink water from potentially contaminated sources such as streams and puddles. This is also helpful in preventing Leptospirosis where animals may have left feces. If you have a cat, keep them indoors to prevent them from getting infected with Giardia or other zoonotic diseases.

If Your Pet Has Giardiasis
Keep your pet isolated from any other animals in the house if they are infected with Giardia. Pick up any feces immediately after your pet has defecated and dispose of it in the trash. Make sure your hands are covered with a glove and/or bag, or that you are using a scooping device (such as with a litterbox).

Since Giardia cysts can persist in the environment, decontamination of the environment is critical to preventing reinfection. Thoroughly wash your hands, clothes, and any objects and surfaces that your sick pet has been in contact with to avoid spreading the parasite to other pets. Follow these CDC guidelines on how to clean and disinfect your home after a pet or family member has been diagnosed with giardiasis.

Reinfection by self-grooming may also occur if any cysts are present on your pet’s fur. Follow your veterinarian’s directions for bathing and E-collar use to minimize the chances of reinfection.

Further Information
For more information on protecting yourself and your pet from zoonotic diseases, check out our articles on Zoonotic Diseases and Parasite Protection for Dogs.

Make an Appointment

Primary Care

AMC’s Primary Care Service aims to provide the highest quality primary veterinary care and to educate our clients about the latest in healthcare and preventative medicine, so they can make informed medical decisions for their pets, enabling their companions to live longer, happier, and healthier lives.

Learn More