Shea Cox
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The Trouble with Puddles
Giardia, not muddy paws
Because Rascal was so small, giardia-caused diarrhea posed a serious risk.

Diarrhea. Boy, do I see lots of this, and when I say “lots,” I mean lots. In fact, on some shifts, it feels like that’s all I see. One of the common causes of diarrhea in dogs worldwide is giardia, a ubiquitous single-celled protozoan parasite. Giardiasis is transmitted by a fecal-oral route, meaning that the parasite is swallowed in food and water (think: puddles, lakes and streams) contaminated with feces. Note: Your pet does not have to eat feces to get the parasite!

Infection can be present without symptoms, but when signs are present, the most common one we see is large volumes of watery feces, oftentimes with blood and mucus. Weight loss, decreased appetite and vomiting can occur as well.

How is the diagnosis made?
Diagnosis is often made by evaluating fecal material under a microscope. However, this little parasite can be difficult to find. So, in addition, we use a nifty “snap test,” adding some stool to a solution that gives us a positive or negative result (like a pregnancy test for poop). This test is very sensitive to the presence of giardia.

How does one treat this parasite?
Generally, easily and inexpensively, provided your dog doesn’t get so ill that he or she needs IV fluids or hospitalization. The little puppy pictured is named Rascal, and he was hospitalized due to an infection with giardia. His diarrhea came on fast and furious, and because teeny puppies don’t have much “wiggle room” when it comes to bodily reserve, it caused a critical drop in his blood sugar. He required more intensive hospitalization, and made a full recovery.

Giardiasis is generally treated with an inexpensive antibiotic called Metronidazole (Flagyl) that is readily available. In small puppies, such as Rascal, or dogs sensitive to this antibiotic, a dewormer known as Panacur can be used instead for five to ten days.

How do I prevent it?
This best way to help prevent infection is to keep your dog from drinking from puddles, lakes, streams or other sources of stagnant water. I know, this can be difficult.

Dog park puddles carry a higher risk than, say, fresh rainwater pooled in a birdbath or fountain. Remember, giardia is transmitted by a fecal-oral route, and what better place to have concentrated levels of feces than a dog park, especially when some pet parents are not diligent about removing their doggy’s waste. Think of it this way: If a dog infected with giardia defecates on the grass, and the rain creates a puddle of water in grass, your dog is essentially drinking a giardia martini.

It may also be advisable to treat other animals in the same household while treating the infected, symptomatic pet. There is a vaccine available for giardia in dogs, but most veterinarians don’t recommend it unless your dog is at really high risk or is one of those pets who gets giardiasis frequently.

Don’t forget: People can get giardia too. Younger children are at a higher risk as hands often find their way to mouths during outside playtime (grass can be contaminated with giardia cysts as well). And those adorable doggy kisses we love so much? Let’s just say that it is easier to accidentally ingest one of those little cysts than you might think.

There are also environmental control measures that can be taken to prevent reinfection. People should be vigilant in clearing fecal material from the environment. If your pet has been diagnosed with giardia, it is often recommended that you wash as many areas of your environment as possible, followed by disinfection with a solution of bleach diluted in water (another measure that is easier said than done).

As with anything medical, there is no one clinical sign that equals a definitive disease, and diarrhea happens to be of the most common clinical signs of any disease process. Because of this, if your pet has diarrhea that persists beyond 24 hours, or is very sudden and severe, a veterinary exam is in order.

And, on that note, I’ll leave you with this closing mantra: No drinka da puddle, no snout in da bay. Pick up poop in da yard, quickly throw it away!


Veterinarian Shea Cox has enjoyed an indirect path through her professional life, initially obtaining degrees in fine arts and nursing. She later obtained her veterinary medical degree from Michigan State University in 2001 and has been practicing emergency and critical care medicine solely since that time. In 2006, she joined the ER staff at PETS Referral Center in Berkeley and cannot imagine a more rewarding and fulfilling place to spend her working hours. In her spare time, she loves to paint, wield her green thumb, cook up a storm and sail. Her days are shared with the three loves of her life: her husband Scott and their two Doberman children that curiously occupy opposite ends of the personality spectrum.

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Submitted by Patricia Teel | March 28 2012 |

We had a wonderful Irish Wolfhound puppy that was 6 months old and we were socializing him by taking him almost everywhere. We took him to the dog park every weekend. We did not allow him to drink from puddles but the article is correct not everyone cleans up well behind their pups. Well it was nasty to say the least. My poor pup did not know what hit him. It was painful and messy. And as hard as the little guy tried to get outside before he could no longer hold it, that was not happening. If any of you know how big an IW puppy is at 6 months then you can guess what a case of explosive diarrhea from an almost three ft tall puppy can do your walls and flooring And the poor baby was in pain and embarrassed because he was housebroken. It was not good for all involved. And I do not use the term explosive lightly. Some of that stuff shot 6 ft away from my poor boy and 5 ft high on the walls.

Submitted by Shea Cox DVM | June 9 2012 |

Hi Patricia~ thanks for sharing your experiences- poor little guy!! (and poor little walls and floors! :). And yes, I can totally believe it! The GI tract can do some pretty impressive things!

Submitted by Julia Kamysz Lane | March 28 2012 |

Great article, Dr. Cox! Wish I'd had it as a resource when our Border Collie puppy, Magnum, had those symptoms when he was 3 months old. When I found blood in his stool, I was so worried. We took him everywhere for socialization, so it's impossible to know how he contracted it. The little guy is now 5.5 months and doing great. As for our light-colored carpet, alas, it did not fare as well. Buh-bye!

Submitted by Shea Cox DVM | June 9 2012 |

Thanks for the comments, Julia! I am glad to hear that your little guy is doing well and no further "growing pains" in your household... well, except for the carpet :).

Submitted by Phyto Z for Dogs | March 28 2012 |

Thanks for the info, Dr. Cox. We have read that when the diarrhea is truly "projectile" the cause is usually giardia.

Submitted by Shea Cox DVM | June 9 2012 |

You are welcome! Thanks for the feedback! :) As an aside, another cause of projectile diarrhea is what is known as Hemorrhagic Gastroenteritis, or HGE. It can look identical, and one of the ways to differentiate is with a negative giardia test. Luckily, the treatment is exactly the same :).

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