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Canine Giardiasis

Giardiasis is an intestinal infection caused by Giardia - one-celled parasites - that invade the gastrointestinal tract and cause diarrhea.

Giardiasis can spread to humans.


Giardia thrives in non-flowing water, such as ponds or lakes. They are transmitted to dogs in two ways:

  1. Drinking contaminated water
  2. Eating or sniffing the contaminated ground

If your dog drinks contaminated water with giardia in the cyst stage, the cysts attach themselves to your dog's intestines and mature inside its body. Eventually, your pet will pass the infective cysts in its stool.

Dogs that hunt prey, such as birds and rabbits, can also get giardia parasites.

The disease is not fatal unless the dog's immune system is young or compromised. Therefore, if there are Giardia cysts in a healthy adult dog's stool, it is usually nothing to worry about. However, in puppies or elderly dogs, giardiasis may cause severe, and possibly fatal, diarrhea if not treated properly.


  • Sudden diarrhea with a green tinge and blood, and then constant diarrhea
  • Vomiting and dehydration
  • Weight loss
  • Lethargy
  • Abdominal pain
  • Fever


To diagnose giardiasis, your veterinarian may perform the following:

  • Examination of a stool sample, using a zinc sulfate fecal flotation test (a regular fecal flotation test might not detect the microscopic cysts)
  • Endoscopy (a procedure using a small, flexible tube to check the abdomen)


After diagnosing giardiasis, your veterinarian will do some or all of the following:

  • Prescribe medicine to kill the giardia
  • Prescribe other medications to treat diarrhea and dehydration
  • Start IV fluid therapy if the dog is dehydrated


  • Don't let your dog drink from streams, ponds, or swamps
  • Avoid public areas polluted with feces
  • Vaccinations are usually only recommended only for dogs with a high risk of contracting the disease

Giardiasis can affect humans. If your dog has Giardiasis, you must disinfect shared areas with bleach and practice good personal hygiene. It is also crucial to be extra careful when cleaning up after infected animals.


In most cases, your dog will recover successfully with proper care.

If not treated promptly in puppies, older dogs, and weak dogs, giardiasis may be fatal.

Medically Reviewed by Sara Ochoa, DVM

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