Giardia is a common intestinal parasite that is spread through the poop of infected animals. Read up on the simple steps you can take to reduce your dog’s risk of infection.

By Sarah Mouton Dowdy
August 24, 2020
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Emma Darvick

If your dog has diarrhea that just won’t go away, don’t ignore it. It could be caused by a common intestinal parasite called Giardia that is spread through the poop of infected animals. 

Treatment typically involves medication (and thorough cleaning) to rid your pet and his environment of the parasite. And while there aren’t any preventatives available for Giardia in dogs, there are simple steps you can take to reduce your dog’s risk of infection. 

What is Giardia?

Giardia duodenalis (also called Giardia intestinalis and Giardia lamblia) is a tiny, single-celled parasite that commonly infects the intestines of dogs. According to the Companion Animal Parasite Council (CAPC), here’s how transmission works:

  1. Animals infected with Giardia shed the parasite in the form of cysts when they poop, contaminating whatever the poop comes into contact with (e.g. soil, water, dog crate, dog bed, fur). These infectious cysts can survive for months in certain environments. 
  2. A new host dog becomes infected when it accidentally eats or drinks these infectious cysts.
  3. Once the cysts reach the dog’s intestinal tract, the parasites emerge from the cysts and begin eating and multiplying.
  4. Some of the parasites will form cyst walls around themselves, and then these cysts will be shed in the dog’s poop to continue the cycle. 

Given how Giardia is transmitted, it’s not surprising that studies have found an increased rate of infection among dogs who visit dog parks. 

Can People Get Giardia?

Paul Diehl, DVM, of Kansas City Veterinary Care in Kansas City, Mo., explains that Giardia is a zoonotic parasite, meaning it can be transmitted to humans. “This is one of the reasons why people are discouraged from drinking water from creeks, streams, and rivers,” he continues. “If an infected animal defecates near [the water source], the parasite cysts in their poop can make their way into the water and infect anyone who swallows them.”

Sounds pretty gross, right? We agree. But if you’re worried about contracting Giardia from your dog, the Companion Animal Parasite Council says humans are much more likely to get the parasite from other humans and that there is little evidence for direct transmission between dogs and people. 

What Are the Symptoms of Giardia in Dogs?

Many dogs infected with the parasite won’t show any outward signs of infection. When Giardia does cause disease, it’s known as giardiasis. Persistent diarrhea is the most common sign of giardiasis, but if left untreated for a long time, weight loss and even death can occur. 

“Giardia often causes very watery diarrhea, so any animal that’s experiencing diarrhea after being exposed to wildlife should be suspected to have the parasite,” Diehl says.

Diagnosis involves using either a microscope to examine the dog’s poop for Giardia, or an enzyme-linked immunosorbent assay (ELISA) test to determine if the poop contains antigens (proteins) that are present on the parasite. 

How is Giardia in Dogs Treated?

After your pup is diagnosed by his veterinarian, he’ll likely be treated with oral medication. In dogs, Giardia is often treated with fenbendazole (a dewormer), metronidazole (an antibiotic), or a combination of both. And sometimes, a combination of multiple medications including febantel, pyrantel pamoate, and praziquantel can also be effective in treating the parasite in dogs. Follow-up testing at your vet may be necessary if clinical signs continue after treatment is complete. 

If your dog is treated for Giardia, it’s important that you pick up and dispose of your pet’s poop as soon as possible to decrease the likelihood of spreading more infectious cysts. On the last day of treatment, you’ll need to give your dog a bath to remove any cysts that might be stuck to his fur, since re-infection is possible if any are still hanging around. You’ll also want to steam-clean or disinfect your pet’s environment—including bedding, carpets, and furniture that he likes to lay on. 

Is It Possible to Prevent Giardia?

Unfortunately, there aren’t any preventative medications available for Giardia in dogs. However, there are things you can to reduce your dog’s risk of infection and reinfection. Diehl recommends removing your dog’s poop from the yard as soon as possible and keeping him from drinking out of potentially contaminated water sources.

“I also recommend bathing dogs after they swim in ponds and lakes,” he adds. “This will wash off parasites that may be stuck in the animal’s fur before the dog licks it and develops an infection.” 

What's the Prognosis after Giardia?

Dogs with giardiasis typically respond well to treatment and don’t suffer lasting effects from the infection. However, geriatric dogs and dogs with health issues in addition to giardiasis are more at risk for serious problems, including death. 

If your dog’s bathroom habits have you concerned that he may have picked up a parasite, don’t hesitate to reach out to your pet’s veterinary team. They can help you determine if your dog needs to be seen in the clinic. Your veterinarian is also the perfect source for more specific tips on how to avoid the parasite in your area.