Giardia is a protozoan parasite that lives in the intestine of affected animals. It is unclear whether there are several species of this parasite or whether there is one species that affect several different animals, including people. These small parasites are very easy to miss on a fecal exam and may not be present in the stool of animals infected with the organism. Repeated fecal exams are sometimes necessary to identify this parasite. Not all animals in which infection can be demonstrated have clinical signs. This leads some people to believe that the parasite may not cause disease . Most vets think that there may just be other factors, like the animal's immune response to the parasite that cause some animals to develop disease and not others. Clinical signs of giardia include weight loss, inability to gain weight appropriately during growth, diarrhoea, vomiting, lack of appetite and greasy appearing stools. Them most commonly used medication for giardia infection is metronidazole (Flagyl). The organisms come from the environment and live in moist to wet areas. They are susceptible to quatenary ammonium disinfectants, Lysol and dilute chlorine bleach. Keeping the dog's environment dry helps a lot.

This disease may be contagious to people from infected dogs so good sanitary practices, like washing your hands after handling an infected puppy, are very important. If a family member develops similar clinical signs, a physician should be consulted.