Giardia in Dogs

What Is Giardia in Dogs?

Giardia is a genus of microscopic single-celled protozoal parasites that cause an intestinal infection in dogs, known as giardiasis.

Certain strains can also affect humans, and infected dogs who are shedding parasites (excreting them in their feces) don’t always show signs. That means your dog could unknowingly transmit this infectious disease to you and your family.

Giardia protozoa are found worldwide, and giardiasis is the most common intestinal parasitic disease in the United States, affecting more than 1 million people per year, according to the U.S. Centers for Disease Control and Prevention (CDC). The infection is also common in dogs, affecting up to 45% in some populations, such as those in kennels.

Puppies younger than a year of age are most likely to have giardia infection symptoms, and immunocompromised dogs are also at an increased risk.

Developing giardia protozoa live in the small intestine and multiply. Infection can cause diarrhea, but veterinarians don’t completely understand why. Giardiasis is characterized by a foul-smelling, soft to watery diarrhea that is often tinged green and may contain blood. Some dogs also experience abdominal discomfort.

The survival rate for dogs infected with giardia is typically good, but puppies, senior dogs, and those with a weakened immune system have an increased risk for complications, including death.

In most cases, giardia in dogs is not considered a veterinary emergency, but puppies and dogs with severe diarrhea should receive emergency veterinary care immediately to prevent dehydration.

Symptoms of Giardia in Dogs

When symptoms of giardia in dogs are present, they may include:

• Sudden foul-smelling, green-tinged diarrhea

• Lethargy

• Decreased appetite

• Abdominal discomfort

• Weight loss

Causes of Giardia in Dogs

Giardia in dogs has two stages in its life cycle. The developing stage is the trophozoite, which changes into the cyst stage. Cysts are passed through an infected dog’s feces into the environment.

Infection occurs by ingesting cysts from contaminated ground, an infected dog’s hind end, or contaminated water. After ingestion, cysts are passed in a dog’s feces in five to 12 days, and they can survive for several months in soil and water.

Giardia duodenalis is the species that causes infection in dogs, and the parasite has different subtypes called assemblages.

The assemblages are typically host-specific, but some can infect both humans and animals. While dogs can transmit giardia to their pet parents, most people are infected by ingesting contaminated water or food.

How Veterinarians Diagnose Giardia in Dogs

To diagnose giardia in dogs, veterinarians will take a pup’s complete history and perform a thorough physical exam.

Provide information about any exposure your dog has had to potential toxins or parasites. Other diagnostic tests your vet may perform include:

• Fecal testing—Fecal tests that are commonly performed to check for intestinal parasites—such as roundworms and hookworms—often can’t detect giardia, but more advanced tests are available to help diagnose the parasite. In some cases, repeated testing over several days may be necessary.

• Parvovirus testing—If you have a puppy or an unvaccinated dog, your vet may recommend a test to rule out parvovirus.

• Blood work—Your veterinarian may recommend a complete blood count (CBC) and biochemistry profile to assess your dog’s:

  • White blood cells

  • Red blood cells

  • Platelets

  • Electrolytes

  • Organ function

  • Hydration status

Treatment of Giardia in Dogs

The goal of treatment of giardia in dogs is to resolve an affected dog’s diarrhea and abdominal discomfort. Treatment strategies often include:

• Fluid therapy—If your dog is dehydrated, intravenous (IV) fluid therapy may be necessary to rehydrate them and correct electrolyte imbalances.

• Medications—Your veterinarian may recommend an antibiotic, an anti-parasitic, or both to treat your dog’s giardia.

• Bathing—Since cysts that your dog has shed can cause reinfection, you must bathe your pup periodically during treatment to prevent recurrence.

• Cleaning—You should also wash your dog’s bedding, disinfect areas where they rest, and dispose of fecal matter as soon as possible.

Recovery and Management of Giardia in Dogs

Most dogs with giardia recover completely in five to eight days, and they should be retested 24 to 48 hours after treatment is completed to ensure cyst shedding is resolved. During giardia treatment, some dogs benefit from probiotics or fiber added to their food.

Since your dog can transmit the giardia infection to you and your family, it’s important to take precautions. Wash your hands frequently, especially after you handle your dog and their fecal matter.

Remove your dog’s fecal matter from the environment as soon as possible. In addition, don’t let children or immunocompromised people clean up after your dog, as these individuals are at a greater risk for infection.

Prevention of Giardia in Dogs

Tips to help prevent giardia in dogs include:

• Monitor your dog—When at dog parks and other public areas, monitor your dog closely and don’t let them into contact with fecal matter.

• Schedule wellness exams—Schedule regular wellness exams so your veterinarian can detect issues, such as intestinal parasites, before they cause health problems for your pup.

• Provide year-round parasite prevention—Parasite prevention, such as Heartgard® and Simparica TRIO™, don’t protect against giardia, but they do prevent other parasites that can impact your dog’s immune system and make them more susceptible to infection in general.

• Vaccinate your dog—A giardia vaccine is available to help prevent infection. Ask your veterinarian if your dog would benefit from the giardia vaccine.