Giardiasis is a common disease that is caused by infection of the gastrointestinal tract with the microscopic parasite Giardia canis. Many different species of animals, including dogs, cats and people, can be infected if they ingest the microorganisms, but the condition is most frequently diagnosed in puppies and young adult dogs. Contact with feces from infected individuals or contaminated bodies of water is responsible for most cases of giardiasis.




Some dogs and cats may carry Giardia within their intestinal tracts and not have any clinical signs of disease, but most individuals with significant infections develop diarrhea. In chronic cases, animals may lose weight and become lethargic. Routine fecal examinations or simple immunological tests may reveal the presence of Giardia organisms in an animal's stools.




Several different types of medication that help infected animals eliminate Giardia parasites are available. Severely affected animals may also require hospitalization, fluid therapy and supportive care, but with appropriate treatment most animals can be expected to recover without any long-term effects. Animals should be bathed at some point during their treatment to remove Giardia cysts from their fur that may lead to reinfections. It is generally recommended that animals testing positive for Giardia be treated even if they do no have any symptoms of infection to reduce the chances of the disease being passed on to people. A Giardia vaccine is available but only reduces fecal shedding of the organism and does not prevent giardiasis, so it is not recommended for most pet animals.


Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008