What is giardiasis?
Giardiasis, sometimes called beaver fever, is the disease that may develop when your dog contracts the parasite Giardia.

The Giardia parasite make a home in your dog’s intestines. Once in the intestines, these parasites interfere with your dog’s ability to breakdown nutrients from food and to absorb nutrients. The most apparent sign of the parasites’ impact on your dog’s ability to breakdown and absorb food is diarrhea.  

Giardiasis can occur in dogs of any age, but young dogs seem most susceptible to the infection. In addition, some dogs may have the parasite but never show any visible sign of the infection. These dogs, however, can still spread the parasite to other dogs.  

What will giardiasis look like in my dog?
The main symptoms of giardiasis are diarrhea and/or watery, sometimes blood-tinged or mucous-tinged stools often accompanied by flatulence. Other symptoms include vomiting, lethargy, and weight loss, especially if the infection has gone unchecked for a considerable length of time.

How does my dog get giardiasis?
The parasite Giardia occurs in two forms: a cyst form and an active or “motile” form. Giardia cysts can be found in many places such as bodies of water from lakes to puddles and practically any surface in which animals already infected with giardiasis have come into contact with. The Giardia cysts are pretty hardy, and they can survive for many months in the environment. Your dog can then contract giardiasis by accidentally ingesting the cysts. This can happen when your dog drinks from a body of water containing the cysts, comes into contact with the feces of an infected dog, shares water or toys with an already infected dog, or even if your dog walks through a Giardia cyst-contaminated surface and later licks his paws. Once inside your dog, these cysts become the motile form of the parasite, and they make a home in your dog’s intestines. 

How is giardiasis diagnosed?
To make a diagnosis of giardiasis your vet will have to examine feces samples from your dog. However, giardiasis can be a surprisingly tricky disease to diagnosis. This is because an infected dog will not shed the parasites in every stool sample, so one negative test result does not definitively mean your dog does not have giardiasis. The best method for safeguarding against false negatives is to use multiple diagnostic methods and to evaluate at least 3 different stool samples from different days. 

There are several methods vets use to evaluate the feces and make a diagnosis. First, your vet may examine the feces under a microscope to look for the parasites. Second, there is a test called a fecal enzyme-linked immunosorbent assay (ELISA) in which the feces is evaluated for substances emitted by the motile form of the parasite. Third, there is the zinc sulfate concentration test in which your dog’s feces sample is placed in a test tube and mixed with a solution of zinc sulfate. After several minutes, if cysts are present, the cysts will float to the top of the test tube.

Finally, it is worth mentioning another diagnostic complication with giardiasis. As explained above, some dogs may test positive for the parasite without having the parasite cause intestinal problems. Thus, it is a possible that a dog may have diarrhea and test positive for the Giardia parasite, but the positive test and the diarrhea are just a coincidence because the diarrhea has been caused by some other problem unrelated to the presence of the parasites. For this reason, positive Giardia tests also need to be evaluated in the context of a dog’s general medical history and physical health. For more about common causes of diarrhea click here.     

How is giardiasis treated?
There are several treatment options for giardiasis, but the medication most commonly used is the antibiotic Flagyl® (metronidazole) which is also helpful in treating some other intestinal parasites and some cases of diarrhea caused by bacteria. Another medication commonly prescribed for giardiasis is Panacur® (fenbendazole) which also is effective in removing some other intestinal parasites. 

Most dogs will respond to treatment. However, it is very easy to become re-infected with these parasites. As an extra measure, if possible, clean surfaces with a solution of bleach and water (1oz of bleach to 32oz of water). Of course, do not let your dog lick or walk through the solution or any household cleaner.   

How is giardiasis prevented?
It is hard to safeguard your dog completely from this infection other than to try to prevent him from coming into contact with potentially contaminated water, feces, objects or surfaces.

There is a Giardia vaccine which is believed to prevent shedding of the parasites and some clinical signs of the infection, but the vaccine will not prevent infection itself. Thus, if there are multiple dogs in your household, your vet may recommend the vaccine as potential way to prevent the parasite from spreading among your dogs.

Can I get giardiasis from my dog?
It is still not definitively known if your dog can infect you with giardiasis. However, some of the research shows it is possible for the cysts to be transferred from dogs to other species. Play it safe by using thorough hygiene and sanitary measures.