Grappling With Giardia: Tips For Avoiding Infection

A grey tabby cat wearing a harness and leash scratching on a tree outside

When pet owners think about protecting their animal from parasites, the first creepy creatures that come to mind are often fleas, ticks, and heartworms. But one less well-known parasite to watch out for is Giardia, which has strains that infect dogs, cats, and even people.

Dr. Meriam Saleh, a clinical assistant professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences, offers advice for protecting pets from this protozoan parasite.

Giardia infections can cause diarrhea, gas, abdominal discomfort, nausea, and vomiting.

While it tends to be more of a threat in other countries, Giardia is also regularly seen in the United States.

“Last year, across the U.S., about 1 in 15 dogs (6.7%) and 1 in 25 cats (4.1%) that were tested for Giardia infections at their vet’s office were positive,” Saleh said.

For context, this makes Giardia more common than some other parasites like whipworms, which were detected in 1 out of every 200 dogs tested at veterinary clinics last year, or roundworms, which were found in 1 out of every 50 dogs, according to the Companion Animal Parasite Council.

Giardia has two lifecycle stages—mature parasites that live in an animal’s intestine and cysts that are shed in feces.

“Cysts are immediately infective when passed in the feces,” Saleh said. “Even very small or microscopic bits of feces can have cysts in them and contaminate objects in the home, the outdoor environment, and the pet’s own fur. If the dog or cat has some feces on their paws and then walks around, paws at its food/water bowls, or scratches its side, the microscopic cysts are contaminating those areas.”

If a pet ingests infected feces or cysts that have spread to another object, Giardia will infect its new host and begin the cycle again.

Even though the parasite can infect multiple species, it usually uses different strains to do so.

“Generally, dogs are infected with canine strains of Giardia and cats are infected with feline strains, but in very rare cases dogs and cats may have strains that have also been found in people,” Saleh said.

While the risk of the parasite spreading to owners, or pets of a different species, is very low, it is still important to take precautions.

“The risk increases in households with a severely immunocompromised person who might be more susceptible to new germs, but it can be decreased by practicing good hygiene for both pets and people, such as washing your hands after picking up or petting your dog or cat,” Saleh said.

While some pets infected with Giardia experience diarrhea and problems digesting food, others show no symptoms at all. Therefore, it’s important to have a pet tested if there is a chance it came into contact with cysts.

“If your dog or cat tests positive for Giardia, your veterinarian will prescribe an oral medication to treat the infection,” Saleh said. “Treatment is usually given anywhere from three to 10 days, depending on the drug being used. In some cases, your veterinarian may prescribe a combination of two or more drugs that are effective against the parasite.”

Fortunately, most pets recover well from Giardia infection with standard treatment. To ensure the parasite is completely removed from the pet’s environment, serious cleaning will be necessary.

“Your veterinarian will recommend that you pick up after your pet and dispose of the feces; use a disinfectant to wash and clean objects and hard surfaces that your pet comes into contact with; and bathe your pet toward the end of treatment to prevent reinfection from any Giardia cysts in their fur,” Saleh said.

Unlike fleas, ticks, and heartworms, Giardia cannot be prevented with a monthly medication. Instead, prevention comes down to maintaining a clean environment and paying attention to the other animals a pet interacts with.

As long as these precautions are taken, your dog or cat safe should be able to avoid infection with this pesky parasite.

Pet Talk is a service of the College of Veterinary Medicine & Biomedical Sciences, Texas A&M University. Stories can be viewed on the web at Suggestions for future topics may be directed to

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