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The Facts about Giardia & Pets

13 Oct 2021
by Dog is Awesome
I first heard about Giardia in dogs when I get my first dog. Giardia was very common where we were living.
After speaking with my vet, I realized that Giardia was not limited to foreign countries. The parasite is found all over the world, but my vet told me not to panic. Luckily, there are many things dog owners can do to prevent their dogs from becoming infected with this unpleasant parasite. Here are the facts about Giardia in dogs you need to know to keep your dogs safe.
The risk of acquiring Giardia infection from your pet is small. However, there are some steps you can take to lower your risk.
Giardia intestinalis (aka: Giardia duodenalis, Giardia lamblia) is a common, microscopic (intestinal) parasite that commonly affects humans, dogs, and cats 1,2.
Common signs and symptoms of Giardia infection (in both humans and pets) are diarrhea, gas, abdominal discomfort, nausea, and vomiting. However, it is possible to be infected and have no signs or symptoms of illness 1,3,4.
What Is Giardia?
Giardia is a single-celled parasite that inhabits the intestines of mammals, birds, and amphibians. There are several different “assemblages” of Giardia, which is the scientific term used to describe the many subspecies of Giardia. Each assemblage targets a specific group of animals, but all Giardia assemblages have the same life cycle and mode of transmission.
The lifecycle of Giardia is composed of two stages. The mature parasites, or trophozoites, live in the small intestine where they multiply and eventually become cysts. Cysts are the infective stage and are shed into the feces of the infected animal. They can survive for several weeks in the environment as cysts, and when they are ingested by an unsuspecting host, they turn into trophozoites and repeat the life cycle. 
Can I get Giardia infection from my pet?
The risk of humans acquiring Giardia infection from dogs or cats is small 4-7. The exact type of Giardia that infects humans is usually not the same type that infects dogs and cats 5-7.
Note: If you own other household or exotic pets, please contact your veterinarian. Seek further information, as some rodents and other species can harbor human strains of Giardia.
How is Giardia spread?
Anything that comes into contact with feces (poop) from infected humans or animals can become contaminated with the Giardia parasite. People and animals become infected when they swallow the parasite. It is not possible to become infected through contact with blood.
How does my dog or cat get infected with Giardia?
Your dog or cat might get infected by:
  • Being in contact with infected feces (poop) from another dog or cat (Always pick up the poop to reduce the risk for other dogs)
  • Rolling and playing in contaminated soil
  • Licking its body after contact with a contaminated surface (for example, a dirty litter box or dog cage or crate)
  • Drinking water from a contaminated creek, pond, or other body of water
Young pets, like puppies and kittens, have a higher risk of illness than adult dogs and cats.
What Does Giardia in Dogs Do?
Giardia in dogs does not always cause problems, but when it does it is highly unpleasant. Giardiasis is the term for the disease caused by the infection, and, as in humans, the most common symptom is diarrhea.
The parasite inhibits your dog’s ability to properly absorb nutrients, water, and electrolytes, which leads to diarrhea and weight loss. The diarrhea can be intermittent or continual, especially in puppies, and failure to diagnose and treat the disease can lead to severe weight loss and even death in extreme cases. The disease is particularly dangerous for puppies, senior dogs, and dogs with compromised immune systems.
Symptoms of Giardia in Dogs
The best way to determine whether your dog has Giardia or another condition is to call your vet. However, there are several symptoms of Giardia in dogs that dog owners should be aware of. These symptoms include:
  • Diarrhea
  • Weight loss
  • Failure to gain weight
  • Vomiting
  • Dehydration
  • Poor coat appearance
Treatment for Giardia in Dogs
If you notice that your dog is having diarrhea, call your vet. Your vet will probably conduct several diagnostic tests to determine if your dog has Giardia and depending on the severity of the case she will discuss a treatment plan tailored to your dog’s needs.
How do I protect myself if my dog or cat has a Giardia infection?
The risk of acquiring Giardia infection from your dog or cat is small. However, there are some steps you can take to minimize your exposure to Giardia if you have dogs or cats:
  • Wear gloves when gardening to reduce the risk of coming into contact with infected feces (poop) or soil.
  • Clean household surfaces regularly.
  • Clean and disinfect areas that your pet has access to—as well as items like toys, bedding, and water and food bowls—regularly.
  • Wash hands frequently and properly:
    • Wet your hands with clean, running water (warm or cold) and apply soap.
    • Rub your hands together to make a lather and scrub them well; be sure to scrub the backs of your hands, between your fingers, and under your nails.
    • Continue rubbing your hands for at least 20 seconds.
    • Rinse your hands well under running water.
    • Dry your hands using a clean towel or air dry them.
If my pet has a Giardia infection, how do I clean and disinfect my house?
Giardia is hard to completely eliminate from the environment, but there are things you can do to decrease the risk of your pets’ reinfection and of human infection.
  • Hard surfaces (for example: cement and tile floors, crates, tables, trash cans, etc.)
    • Cleaning
  • Wear gloves.
  • Remove feces and discard in a plastic bag.
  • Clean and scrub surfaces using soap. Rinse surface thoroughly until no obvious visible contamination is present.
    • Disinfection
  • Wear gloves.
  • Disinfect according to manufacturer guidelines using one of the following:
  • Quaternary ammonium compound products (QATS) 4, which are found in some household cleaning products; the active ingredient may be listed as alkyl dimethyl ammonium chloride.
  • Bleach mixed with water (3/4 cup of bleach to 1 gallon of water)8
  • Follow product instructions, ensuring the product stays in contact with the surface for the recommended amount of time.
  • Rinse with clean water.
    • Washer and Dryer
  • Clothing, some pet items (for example, bedding and cloth toys) and linens (sheets and towels) can be washed in the washing machine and then heat-dried on the highest heat setting for 30 minutes.
  • If a clothes dryer is not available, allow clothes to thoroughly air dry under direct sunlight.
How do I reduce the amount of Giardia in my yard or outdoor environment?
Giardia is hard to completely eliminate from the environment, but there are things you can do to help decrease the risk of pet reinfection and of human infection. Please remember that despite your best efforts to clean the environment, Giardia can persist in outdoor spaces and pet reinfection is possible4.
  • Wear gloves when handling feces.
  • Remove feces promptly 4 and put them in a plastic bag.
  • Limit access to common outdoor spaces, where possible, if pets have diarrhea or are being treated for Giardia.
  • Eliminate any source of standing water (for example, puddles, containers with water, and fountains that are not in use).
  • Do not attempt to use bleach or QATS in your soil or grass area, as they will be ineffective.
  • Do not allow any new animals, especially young ones, to enter the yard or other outdoor space until advised by your veterinarian.
How do I prevent my dog or cat from getting re-infected, or sickening my other pets, during treatment?
  • If you have other dogs or cats, make sure you tell your veterinarian even if they are not showing signs of diarrhea. Other pets may also be put on medicine depending on the situation. Even animals showing no signs of Giardia infection could be infected and shedding Giardia into the environment 4.
  • Bathe all household pets with pet shampoo following medical treatment to ensure no fecal residue is in the pet’s coat 11.
  • Clean dogs’ and cats’ environment, as described above, 11 (holding areas, floors, crate, etc.) and wash water bowls daily with soap and water.
  • Limit your dog’s access to untreated surface water (creeks, ponds, lakes) to avoid re-infecting your animal and contaminating the water which could make other animals sick.


  1. The Merck Veterinary Manual. Overview of giardiasis.External United States: Merck; 2016.
  2. Thompson, RCA. The zoonotic significance and molecular epidemiology of Giardia and giardiasis.External Vet Parasitol. 2004;126(1-2):15-35.
  3. Ballweber LR, Xiao L, Bowman D, Kahn G, Cama VA. Giardiasis in dogs and cats: update on epidemiology and public health significance.External Trends Parasitol. 2010;26(4):180-9.
  4. Tangtrongsup S, Scorza V. Update on the diagnosis and management of Giardia spp infections in dogs and cats. Cdc-pdf[PDF – 8 pages]External Top Companion Anim Med. 2010;25(3):155-62.
  5. Berrilli F, Di Cave D, De Liberato C, Franco A, Scaramozzino P, Orecchia P. Genotype characterisation of Giardia duodenalis isolates from domestic and farm animals by SSU-rRNA gene sequencing.External Vet Parasitol. 2004;122:193-9.
  6. Feng Y, Xiao L. Zoonotic potential and molecular epidemiology of Giardia species and giardiasis.External Clin Microbiol Rev. 2011;24(1):110-40.
  7. Xiao L, Fayer R. Molecular characterisation of species and genotypes of Cryptosporidium and Giardia and assessment of zoonotic transmission.External Int J Parasitol. 2008;38:1239–55.
  8. Erickson MC, Ortega YR. Inactivation of protozoan parasites in food, water, and environmental systems.External J Food Protect. 2006;69:2786–808.
  9. Olson ME, Goh J, Phillips M, Guselle N, McAllister TA. Giardia cyst and Cryptosporidium oocyst survival in water, soil, and cattle feces.External J Environ Qual. 1999;28(6):1991-1996.
  10. DeRegnier DP, Cole L, Schupp DG, Erlandsen SL. Viability of Giardia cysts suspended in lake, river, and tap water.External Appl Environ Microbiol. 1989;55(5):1223.
  11. Fletcher R, Deplazes P, Schnyder M. Control of Giardia infections with ronidazole and intensive hygiene management in a dog kennel.External Vet Parasitol. 2011;187(1-2):93-8.
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