Giardia is a highly infectious microscopic parasite that can cause severe gastrointestinal (GI) disease. Our Emerald Animal Hospital team believes in providing exceptional care for our patients, which includes educating their owners. Here, we provide answers to frequently asked questions about Giardia in dogs.

What is Giardia in dogs?

Canine giardiasis is a protozoal infection caused by Giardia duodenalis. The ubiquitous, highly infectious microscopic organism can live in the environment for many months in the right conditions, and has been identified worldwide. 

Genetic studies have improved the understanding of Giardia species’ host-specificity. G. duodenalis is a single species that has at least eight genotypes (i.e., A through H) that are referred to as assemblages. Assemblages A and B are found in humans and animals, and some subtypes in these assemblages are considered zoonotic (i.e., they can be transmitted between animals and people). Other assemblages have a higher host specificity and can’t be passed between different species. Assemblages C and D predominate in dogs.

How is Giardia transmitted in dogs?

Giardia has two stages. The trophozoite stage is the parasitic form that attaches to the dog’s intestinal epithelial cells and differentiates into the cyst stage (i.e., the infectious form) after entering the colon. Cysts are shed in an infected dog’s feces, and can survive for months in the environment. Typically, dogs are infected by ingesting feces or feces-contaminated food or water, but transmission can also occur through contact with contaminated items, or when grooming feces-soiled fur. Some affected dogs are subclinical carriers who don’t exhibit signs, but shed the parasite in their environment. Young dogs, especially puppies younger than 6 months, are at increased risk for clinical disease, while young dogs housed in a densely populated environment, such as a kennel, are at highest risk.

What are Giardia signs in dogs?

As mentioned, some infected dogs exhibit no clinical signs, but when signs are present, they include acute onset diarrhea that is often pale, foul-smelling, and contains fat or mucous, lethargy, and decreased appetite. In some cases, dogs develop chronic diarrhea that can lead to weight loss. Infection does not provide immunity, and dogs can be reinfected if their environment continues to harbor Giardia cysts. 

How is Giardia diagnosed in dogs?

If your dog has diarrhea, Giardia is included in our rule-out list. Diagnostics include:

  • History — Our team takes a detailed history to determine if your dog may have been exposed to a pathogen such as Giardia.
  • Physical examination — We examine your dog from nose to tail, assessing their hydration status, temperature, and other important parameters.
  • Blood work — We may perform a complete blood count (CBC) and biochemistry profile to evaluate your dog’s overall health. 
  • Fecal check — Our team obtains fresh feces from your dog to test for Giardia and other parasites. Since Giardia cysts can be shed intermittently, we may request several fecal samples over five to seven days to ensure we identify the organism.

Since dogs can shed Giardia cysts and not show disease, a positive Giardia fecal test does not prove that giardiasis is causing your dog’s diarrhea, but a positive test does warrant Giardia treatment.

How is Giardia treated in dogs?

Giardiasis treatment  in dogs involves:

  • Medications — An anti-parasitic and antibiotic drug combination is often prescribed.
  • Fluid therapy — A dog with severe or chronic diarrhea may need fluid therapy to replace fluid deficits and restore electrolyte imbalances.
  • Bathing — Dogs should be bathed at the beginning and end of treatment to remove Giardia cysts from their coat.
  • Environmental management — To prevent reinfection, your dog’s environment should be thoroughly disinfected, and bedding and upholstery where they rest should be machine washed or steam cleaned.
  • Retest — Your dog will likely need retesting to ensure their infection has cleared.

How is Giardia prevented in dogs?

Tips to decrease your dog’s Giardia risk include:

  • Wellness examinations — Schedule regular wellness examinations, so our team can evaluate your pet for conditions such as giardiasis.
  • Pack water — On outings, pack water and a portable water bowl so your dog can drink uncontaminated water. Never allow them to drink from natural water sources or bowls left on the sidewalk.
  • Feces removal — Remove feces from your yard regularly.
  • Feces avoidance — When outdoors with your dog, don’t allow them to investigate other animals’ fecal material.
  • Research kennels — Before boarding your dog, research the kennel to ensure they practice appropriate environmental hygiene that helps prevent Giardia outbreaks.

Can I get Giardia from my dog?

Some Giardia assemblages can be transmitted from dogs to humans, but those that most commonly affect dogs have not been reported in humans. Most human giardiasis cases are caused by drinking contaminated water. However, if your dog has Giardia, wear gloves when you handle them or their feces, wash your hands thoroughly after any contact, and frequently clean and disinfect the environment until your dog’s infection is cleared. 

If your dog has diarrhea, contact our Emerald Animal Hospital team, so we can determine if Giardia is causing the problem and administer the appropriate treatment.