What is Giardia?

Giardia is a common intestinal parasite in dogs and cats. Many dogs and cats have this parasite in their intestines without any problems. However, susceptible animals, such as young animals or animals with reduced resistance can become ill from Giardia. The most common symptoms are intermittent to persistent diarrhea, blood and/or mucus in the stool and sometimes vomiting, reduced appetite and lethargy.

Not all animals with giardia have symptoms, but they can distribute the parasite with the feces. These Giardia then end up in the environment where an another animal can get infected when they accidentally eat the parasite. This can happen by eating grass in the park, drinking from puddles or by licking on the paws. You can also bring it in yourself on your shoes, this way even cats that don’t come outside can get infected.


When we suspect an infection with giardia in a dog, the diagnoses is made by a fecal examination in our clinic. In case of acute diarrhea we would like to examine the stool sample on the second (or later) day after the clinical signs occurred.
It is not recommended to examine the feces of healthy dogs for giardia, as the parasite may be present in the intestines of healthy dogs.


In the treatment of Giardia it is important that we treat both the animal and the environment.

  • We will start with treating the Giardia with Panacur (Fenbendazole) for 3 days. Because healthy animals can excrete the parasite and re-infect the animal that is ill, we recommend that all animals in the household are treated with Panacur.
  • To treat the diarrhea and optimize the immune system in the intestines, we recommend giving easily digestible food (Hill’s I/D) and pro-biotics.
  • Because there is a risk that the animal will re-infect itself, it is wise to wash him/her with a dog/cats shampoo on the third day of treatment and repeat this after two days.
  • Sometimes it is necessary to repeat the Panacur or to use a second medicine (metronidazole) if the panacur has worked insufficiently.

Treatment of the environment:

Giardia can remain infectious in the environment for a long time, so it is possible that the dog or cat may get re-infected. The colder and more humid the environment is, the longer the Giardia can remain contagious.

  • Hot water can kill the parasite. It is therefore important to wash the blankets as often and as hot as possible.
  • Water and food bowls should be washed with boiling water every day. Leave the boiled water in for at least 1 minute. This also applies for the litter box.
  • Chlorine or Quaternary ammonium salts can kill the parasite, and can be used for cleaning the environment. This should be allowed to soak in for at least 5 minutes and rinsed thoroughly.

Some Giardia strains can also be contagious for humans. Good hygiene is therefore very important. Wash your hands after contact with your pet.

If you have any questions, please feel free to contact us. You can also download this information: Treatment information Giardia