Giardia in Puppies

A Nasty Little Parasite

Young woman walking with pet puppy poodle
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Giardia can cause devastating health problems in puppies. Similar to the protozoan coccidia, canine giardia infection typically affects younger dogs with underdeveloped immune systems, making them prone to diseases that older dogs can fight off.

What Is Giardia?

Giardia infection, or giardiasis, is caused by ingesting giardia, single-cell organisms (protozoan) that parasitize the small intestine. Puppies tend to contract the organism by drinking from streams, puddles, or other contaminated water sources. In fact, giardia is quite common in young pets—affecting up to half of all puppies. And if left untreated, the intestinal parasite can wreak havoc on a puppy's digestive tract, causing allergies or malabsorption issues which lead to malnutrition.

Symptoms of Giardia in Puppies

If 5 to 10 days after a hike in the woods your puppy suddenly comes down with a case of diarrhea, giardia could be the culprit. The stool may be mixed with mucus and blood or it may appear unusually soft and light colored. Indigestion, refusal to eat, and a swollen tummy from gas and bloating may all present as symptoms. If the infection persists, a puppy may have trouble gaining or maintaining weight, as the organism compromises its ability to properly process food. Of course, many asymptomatic cases are diagnosed, as some dogs may show no sign of illness, yet still be infected. If you feel something's off with your pup or his digestion, call your vet to schedule an appointment.

illustration of signs of giardia in puppies
Illustration: Elnora Turner. © The Spruce, 2018

Causes of Giardia

The infective cyst stage of the giardia organism lives in the environment, mostly in standing water. When infected animals, like deer or small mammals, defecate near water sources, the water acts as a medium for contracting the bug. The disease is also spread through contact with infected feces. Once the puppy is infected, the protozoa attach to its small intestine and begin a parasitic feeding stage. The parasite then begins to divide and replicate itself causing distress to the puppy and sometimes destruction of the intestine.


Diagnosing giardia begins with a stool sample collected either at home or at the veterinarian's office. Using a microscopic examination, the veterinarian looks for the protozoan in the sample. Diagnosis can be tricky because infected dogs pass the organism only intermittently and a fresh stool test can be negative, even when giardia is present. Repeated tests are often necessary to detect the tiny parasite.

Technically, there is no drug specifically formulated for treating giardiasis in animals. So, giardia is typically treated with the prescription drug fenbendazole, a broad-spectrum anti-parasitic medicine used to also treat other gastrointestinal parasites like worms. Side effects rarely occur with this course of treatment and the drug use is safe for both pregnant and lactating animals. Following a course of medication, repeated fecal exams are needed to confirm the presence of any existing organisms. To prevent the spread of giardia from your puppy to your family members, bathe him regularly, with gloved hands and shampoo, to remove fecal material and the associated cysts.

Giardia and Humans

If your puppy has giardia, there's a good chance he could pass it onto his loved ones. Giardia is zoonotic, meaning it can be transmitted from animals to humans and then back again. The symptoms in humans are similar to canines and include diarrhea, gas, greasy stools, and other digestive issues. If you suspect a human infection, have your doctor test all family members, so that treatment can begin immediately. Young children, elderly adults, and anyone with a compromised immune system are especially at risk.

How to Prevent Giardia

You can prevent the chance of giardiasis by keeping your own yard clean of feces. Environmental areas like grass and standing water are tough to decontaminate, but when you're out and about, restrict your dog's access to unsanitary water to help prevent the chance of infection.

If your puppy was infected, do your best to clean any outdoor surfaces where it frequently defecates with a bleach-based cleaning product. If possible, remove and replace any rocks or other outdoor items it may have come into contact with. And wash all dog beds in hot water and laundry detergent. The more you can clean any home items that may harbor contamination, the healthier the outcome for your family.

Giardia also commonly occurs in kennels and boarding facilities where the disease spreads rapidly due to the crowded conditions. So, don't board your dog until it's about a year old.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.