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Understanding Giardia

If you've ever brought your dog to a daycare or dog park, you've probably heard of Giardia. Dreaded by pet parents and pet care providers alike, a giardia infection can cause serious illness, uproot your daily routine and even disrupt businesses.

Giardia is a parasitic disease that can cause gastrointestinal issues in dogs, cats, and even humans. In this comprehensive guide, we will explore what Giardia is, how it spreads, and most importantly, how to prevent and treat it.

What is Giardia and how does it affect pets and humans?

Giardia is a microscopic parasite that can reside in the intestines of dogs and cats. These parasites are shed through feces in the form of hardy cysts that can survive in the environment for extended periods. Pets infected with Giardia may not always show symptoms, but when they do, they can experience diarrhea, gas, abdominal discomfort, nausea, and vomiting. Blood and mucous in a loose stool is usually the first sign of a giardia infection in pets.

Can pets transmit Giardia to humans?

According to the CDC, the risk of humans contracting Giardia from pets is relatively low. The strain of Giardia that affects humans is typically different from the one that infects dogs and cats. However, some strains can be shared between humans and animals.

What is the Life Cycle of Giardia?

Giardia is not a bacteria, virus or an animal. It is a microscopic, single celled organism called a protozoa. The life cycle of Giardia involves two stages: the active trophozoites causing infection in the intestines, and the inactive cysts passed in the feces. Once they are passed, the cysts are ready to infect a new host. Cysts are encased in a protective shell, and can survive in cool and damp environments for months, making them a source of infection and reinfection for animals, especially in crowded conditions. Cysts are resistant to most forms of disinfectant commonly used, and can even survive some types of chlorinated disinfectants.

How does Giardia spread?

Giardia spreads through the fecal-oral route, which means anything contaminated with infected feces can transmit the parasite. Both humans and animals become infected when they accidentally ingest Giardia cysts. This can can happen after a pet drinks from a puddle, or walks on contaminated soil and later licks their paws. Giardia can be spread between pets within a home through a litter box. Cysts can stick to a pet's fur after elimination and can be transferred throughout the home. Giardia is very contagious between dogs and can be spread through a shared environment or even close physical contact during play. Even though giardia is not present in saliva, it may be possible for a dog infected with giardia who has licked themselves recently to spread giardia by licking other dogs or humans. Medications that treat the trophozoites in the intestines, may not be effective against the cyst inside the host, and therefore infectious cysts may be shed intermittently long after a clinical infection has been resolved. This means your dog or cat may continue to shed cysts in your household for weeks after treatment, and may be at risk for re-infection. How can I prevent my pet from getting Giardia?

The most common ways pets become infected is by drinking contaminated water or licking dirty paws. You may not be able to prevent your pet from being exposed to giardia, but there are some simple things you can do to minimize risk:

  1. Wipe paws with a gentle baby wipe or dog grooming wipe when your pup comes inside from a walk. Our pups are exposed to a wide variety of chemicals, debris, and diseases every time they go outside. Not only will you prevent them from tracking dirt and germs in the home, but you can prevent your dog from ingesting harmful debris or parasites when they lick their paws.

  2. Don't share water bowls in public spaces. It might seem thoughtful when a business leaves a water bowl on the sidewalk on a hot day, but unless it was just cleaned and refilled, you don't know if the water has been contaminated. This includes the dog park. Only let your dog drink from a fresh bowl of water that other dogs have not drank from. When giving water to multiple dogs in a public space, rinse the bowl out and give fresh water to each dog.

  3. Prevent your pup from drinking from ponds, puddles, and any other potentially contaminated water source. This usually means providing fresh water for them so they won't be motivated by thirst to drink out of a pool or puddle.

Here are some steps you can take to minimize the risk of spreading a Giardia infection:

1. Wash your hands with soap and water for at least 20 seconds after handling your pets, or cleaning up their waste. This simple practice can significantly reduce the chances of transmission.

2. Clean and disinfect surfaces and items that your pets regularly use, such as toys, bedding, water, and food bowls. Regular cleaning can help prevent the spread of the parasite in your home.

3. Limit exposure to others. If your pets are diagnosed with Giardia or have diarrhea, limit their access to common outdoor spaces like dog parks or public trails. Test your pet's stool at 2 and 4 weeks after treatment, and do not send your dog to daycare, boarding or have them walked with other dogs until cysts are no longer present. Notify your groomer of an infection prior to booking an appointment so they can take steps to prevent their other clients from being infected. These steps can prevent re-infection and protect other animals from potential contamination.

4. Treat all pets in your household. If one pet has been diagnosed with giardia, it is likely that all of your pets have been exposed.

5. Bathe all household pets using pet shampoo following medical treatment. Regular bathing of your pets, particularly with a shampoo containing chlorhexidine digluconate, can help remove cysts from their fur.

6. Use baby wipes, or dog grooming wipes to wipe your pet's butt after they potty, and dispose of the wipes immediately. Do not use disinfectant wipes on your dog.

Treatment of Giardia infection in pets:

If your pet experiences persistent diarrhea or other concerning symptoms, seek veterinary care immediately. Treating Giardia requires professional guidance, and over-the-counter treatments are not recommended.

Treatment for Giardia typically aims to address clinical signs and reduce cyst shedding rather than eliminating it entirely. Fenbendazole, metronidazole, and albendazole are common antiparasitic medications used for treatment. Fenbendazole is approved for use in dogs and is safe for pregnant and lactating animals. Metronidazole can be considered for dogs and cats, but it has been associated with adverse effects in dogs with chronic or high-dose treatment. Albendazole is not recommended for dogs or cats due to possible bone marrow suppression. Your veterinarian will determine the most suitable course of action based on your pet's specific condition.


Giardia infection in pets requires prevention, timely treatment, and veterinary consultation. Understanding how it spreads and maintaining good hygiene can protect both pets and humans. Regular check-ups and a clean environment are vital for their well-being. Always consult a veterinarian if you suspect infection.

Sources: Centers for Disease Control and prevention (CDC): Merck Veterinary Manual:,the%20chronic%20phase%20of%20infection.

[Note: Always consult with a licensed veterinarian for specific advice on your pet's health and treatment.]

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