to Pet Health Network or

Answers from vets about your dog:

Giardia 101

Reviewed by Peter Kintzer, DVM, DACVIM on Monday, April 14, 2014
Posted April 11, 2014 in Dog Diseases & Conditions A-Z

For such a tiny parasite, Giardia is significant and swings a wide swath among people and animals alike. 

What is Giardia?
Giardia is a microscopic, protozoan parasite that causes inflammation of the intestinal tract and subsequent diarrhea that can be very serious. It has been referred to as backpackers’ disease because of the risk of exposure when hiking.

How common is Giardia?   
Giardia is common in pets. The Companion Animal Parasite Council reports that while “regionalDog in Grass differences in Giardia prevalence exist, infections in dogs with clinical signs averaged 15.6%.”

Giardia is a worldwide health concern -- particularly in developing countries. According to the CDC, even in developed countries, giardia affects nearly “2% of adults and 6% to 8% of children.” In undeveloped countries it can be much higher, owing to the lack of availability of clean water.

How does it spread?
Giardia is transmitted by oral ingestion of water or food that has been contaminated by stools of infected people and animals.

What are the signs of Giardia?  
Acute infection after exposure can last from 1-2 weeks. The clinical signs of Giardia in animals and people are very similar and may include:

  • Diarrhea
  • Gas
  • Greasy stools that tend to float
  • Stomach or abdominal cramps
  • Upset stomach or nausea/vomiting
  • Dehydration (loss of fluids) and weight loss

How is Giardia diagnosed?

  • Smear — Sometimes the immature trophozoites can be seen in a smear of the feces under a microscope. Because they are only passed intermittently, even in symptomatic dogs, multiple smears over time must be done; still, they may fail to reveal the parasites.
  • Fecal flotation — Fecal floatation for cysts is more diagnostic, but the trophozoite stage won’t be seen by floatation—the floatation solution destroys the trophozoites.
  • ELISA and IFA assays — Assays for Giardia antigens in feces are the most diagnostic test we have available. They are very sensitive, easy to run and very specific tests.

All dogs with clinical signs of Giardia should be tested.

How is Giardia treated?
There is no approved treatment for Giardia in animals. Metronidazole is the most commonly used extra-label therapy, but is often ineffective. Authorities recommend a combination of drugs that are available to veterinarians for other indications. Effective treatment involves metronidazole in combination with a drug called fenbendazole. Following appropriate treatment, infected animals should be retested for response. The CAPC also recommends  that bathing accompany treatment.

Can I get

Share This Article

Mike has more than 35 years of experience in companion animal veterinary practice and is a valued member of IDEXX’s Pet Health Network team since 2013.