Purina-Dog-Content-Brand Giardia and cryptosporidium are two pesky parasites that can affect an animal’s small intestine, causing diarrhea and cramping. These nasty organisms are transmitted when a form of the parasite called the cyst is shed in one animal’s stool and consumed by another dog or cat.

Dwight Bowman, a professor of Parasitology at Cornell University, says that when the animal ingests drinking water or puddle water or pond water, or eats something that’s contaminated with the cyst, they can get infected. He says that if your dog has diarrhea, diagnostic tests will help determine the cause.

Fortunately, if giardia is to blame, you don’t need to worry about picking it up from your pet. Bowman says there’s no evidence that the species infecting dogs also infects humans.