If your dog has been having tummy issues and you can't figure out the cause, they could have giardiasis, an infection caused by tiny parasites called giardia. Giardia is among the most common intestinal parasites reported in dogs, but they can wreak havoc on your dog's digestive system.
Here's everything you should know about giardia in dogs, including how a veterinarian identifies them and giardia in dogs treatments.
What Is Giardia?
Giardia requires a host — in this case, a dog — to live and multiply. There are two forms of giardia: the single-celled trophozoite (parasite) that swims around and lives in the small intestine of mammals, and the other is a cyst, or egg. A cyst passed in the feces of an infected animal is considered immediately infectious to other animals. Dogs contract giardiasis when they ingest a giardia cyst, either directly from the soil or from contaminated water.
Giardia are found everywhere in the U.S. but are more common in the western U.S. and in wet areas. Dogs living in stressed or crowded conditions, like animal shelters, have a higher risk of contracting the infection due to the close proximity they have to other dogs.

How Giardia in Dogs Gets Diagnosed
Giardia in dogs can be tricky to diagnose because, while in some cases, it can cause gastrointestinal issues (usually diarrhea), but in other cases it won't cause any problems at all. Doggy diarrhea as a result of giardia can either come on suddenly, come and go, or last for a long time. Giardia in dogs is probably far more common than we realize both because it doesn't always cause health issues and because giardia organisms can be tough to identify.
Your vet will be able to diagnose your dog with giardiasis either by identifying giardia organisms or giardia antigens in your dog's feces. Go with whichever test your dog's vet recommends; they may even recommend both tests since giardia are notoriously difficult to find in fecal samples. In fact, you may have to bring in several samples before the vet can find the critters.
If your dog has chronic diarrhea and the vet can't find giardia, they may still recommend giardia treatment if they suspect your dog is infected.