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Giardia in Dogs

Learn all about Giardia in dogs and how to prevent and treat the disease it causes.

Giardiasis is a clinical condition characterized primarily by chronic diarrhea. This condition is caused by the microbe Giardia lamblia (also known as G. intestinalis or G. duodenalis), a single-celled parasite that can affect dogs, cats, and humans alike. This zoonotic disease most commonly affects puppies and does not always cause giardiasis or its symptoms. It is most commonly spread through the consumption of substances that have been soiled with infected feces.

Giardia prefers cool and moist environments, so it often spreads through shared drinking water. When Giardia does cause symptoms in a pet or human, it most often causes generic signs of gastrointestinal distress. Common symptoms of giardiasis include:

  • Acute, chronic or recurring diarrhea
  • Soft, light-colored, greasy stool with particularly foul smell
  • Blood or mucus in the stool
  • Malnutrition
  • Vomiting
  • Dehydration and/or weight loss (caused by excessive diarrhea or vomiting)

Diarrhea in Dogs: Is Giardia the Cause?

One study that utilized samples from upwards of 90 veterinary clinics throughout Canada revealed that 16% of dogs with gastrointestinal symptoms were confirmed as being infected with the Giardia parasite. Of these dogs, 17.1% exhibited vomiting; and, in 38.4% of infected dogs the infection persisted for more than a week (Carlin, Bowman, Scarlett, Garrett, & Lorentzen, 2010). Though this study utilized the SNAP fecal enzyme-linked immunosorbent assay (ELISA) test to diagnose dogs and cats, it is more common for veterinarians to assume an infection based on the negative diagnosis of more common causes of gastrointestinal symptoms.

Veterinarians examining a pet that is suffering from gastrointestinal symptoms may test for maldigestion, malabsorption, or inflammatory bowel disease before considering giardiasis as the culprit. Your veterinarian may request a blood test or a standard fecal exam. Though the aforementioned ELISA test has a 95% chance of detecting the parasite in an infected patient, standard fecal tests have only a 70% chance of doing so.

This deficiency is largely due to the fact that the Giardia parasite only passes through the digestive tract intermittently. Woolf states in her Dog Owner's Guide (2014) that veterinarians that do not have the ELISA test available to them may instead take three fecal samples within five consecutive days, which can increase the chance of detection to 90%.

Prevention: Sanitary Practices and the Zoonotic Potential of Giardia

A national survey conducted in 2009 revealed that Giardia is present in the fecal matter of 4% of all dogs in the United States, regardless of whether or not the dog displayed symptoms of gastrointestinal distress (Little et al., 2009). Though the same species of Giardia afflicts humans, cats, dogs, cattle, rats, and other mammals- there are at least seven distinct assemblages of the parasite, many of which are found exclusively in a single mammalian species (Sahatchai & Scorza, 2011).

Due to this genetic variation and the nature of its fecal-to-mouth transmission, Giardia seldom passes from dogs to humans or from dogs to cats (“Parasites - Giardia,” 2012). As dogs are prone to coprophagia, it is important to prevent dogs from interacting with fecal matter whenever possible. It is also important to maintain a sanitary environment even if your dog appears to be perfectly healthy, as Giardia can be present in dogs without presenting symptoms.

Standard disinfectants and chlorine bleach can be used to treat areas soiled by your pet to kill cysts, thereby preventing the spread of the disease. Any pet positively diagnosed with the bacteria can have it eliminated from their fur with a standard bath. While being treated, infected dogs should be isolated in an area that is easy to disinfect.

It is possible to prevent giardiasis with vaccination; however, it is not recommended that all pets receive this treatment. If your dog is regularly exposed to potentially infested water, such as a lake or other body of water that is not properly cleaned and regulated, then the vaccination may prove useful. Dogs that are regularly placed in kennels where drinking water is shared with many unfamiliar dogs may also benefit from the vaccination (“Current Advice on Parasite Control: Intestinal Parasites - Giardia,” 2013).

Treating Giardia infections with select medications can also prevent its spread to healthy dogs. While many veterinarians may simply treat the symptoms of giardiasis until they subside, this protocol may allow for dogs to carry the parasite and facilitate its spread.

Treating Giardiasis

Dogs suffering from gastrointestinal symptoms may benefit from standard treatments such as probiotic supplements and a simple diet of boiled chicken mixed with white or brown rice. It is also important to prevent dehydration by providing plenty of water and avoiding food or treats that contain ingredients that may upset the stomach further. Additionally, your veterinarian may provide you with a solution containing kaolin or pectin to treat your pet’s diarrhea.

Dogs in a multiple pet household may also be given medication to prevent the shedding of Giardia cysts, which may otherwise occur even after symptoms subside. Common medications used to treat Giardia include metronidazole, albendazole, and fenbendazole. Metronidazole can be taken orally to treat giardiasis as well as other diarrheal disorders, such as inflammatory bowel disease. This medication can also provide benefits to your pet’s dental health and is used to treat periodontal disease in dogs.

Albendazole treats diseases caused by certain parasites, including Giardia, and can combat the infestations of the parasites themselves. In addition to treating infestations of Giardia, it can also be used to treat infestations from roundworms, tapeworms and flukes. Fenbendazole also treats a variety of parasites including hookworms, whipworms, and certain tapeworms. Your veterinarian may recommend any of these three medications; however, fenbendazole is most commonly used due to the fact that its potential side effects are minimal (“Selected Zoonotic Agents of Gastroenteritis That Can Be Acquired From Dogs and Cats: Giardia,” n.d.).

Facts to Remember:

  • Giardia is most commonly spread through infected drinking water, so it’s important to always ensure your pet has clean water
  • Giardia is spread through fecal matter, so it is important to thoroughly disinfect surfaces that have been soiled with feces
  • Giardia can be spread to humans and other pets, so it’s important to exercise caution when cleaning up after a pet
  • Giardia can cause diarrhea, vomiting, and other gastrointestinal problems- or it can cause no symptoms at all, so it is important to protect against its spread at all times


Carlin EP, Bowman DD, Scarlett JM, Garrett J, Lorentzen, L. (2010, Jun). Prevalence of Giardia in symptomatic dogs and cats throughout the United States as determined by the IDEXX SNAP Giardia test. Vet Therapeutics 7(3):199-206. Retrieved from

Current Advice on Parasite Control: Intestinal Parasites - Giardia. (2013, May 1). Retrieved from

Little SE, Johnson EM, Lewis D, Jaklitsch RP, Payton ME, Blagburn BL, Bowman DD, Moroff S, Tams T, Rich L, Aucoin D. (2009, Aug 9). Prevalence of intestinal parasites in pet dogs in the United States. Vet Parasitol 166:144- 152, 2009. Retrieved from

Parasites - Giardia. (2012, July 18). Retrieved July 1, 2015, from

Sahatchai, T., & Scorza, V. (2011, August 1). Update on the Diagnosis and Management of Giardia spp Infections in Dogs and Cats. Retrieved July 9, 2015, from

Selected Zoonotic Agents of Gastroenteritis That Can Be Acquired From Dogs and Cats: Giardia. (n.d.). Retrieved from

Woolf, N. (2014). Dog Owner's Guide: Giardia. Retrieved July 9, 2015, from