Giardia refers to microscopic protozoan parasites, primarily
Giardia duodenalis (also known as
G. intestinalis or
G. lamblia), that cause the intestinal disease called giardiasis. Giardiasis can affect a wide range of domestic and wild mammals including dogs, cats, cattle, sheep, goats, horses, pigs, beavers, coyotes, rabbits, rodents, and raccoons, as well as humans. Various other Giardia species also infect birds, reptiles, and amphibians.
Giardiasis is characterized by acute or chronic diarrhea; however, many infected hosts (especially adult animals) can have no symptoms but still carry and shed the parasite. The parasite is found in the intestinal tract of infected animals and people and is shed in feces. It is found in every region of the United States and throughout the world.
Zoonotic Potential & Genetic Types
There are at least six species of
Giardia that infect animals. In most mammals, giardiasis is caused by
Giardia duodenalis, which is the only species known to cause illness in humans. However, within
G. duodenalis, genetic types usually differ between human and domestic animal (livestock and pet) infections.
G. duodenalis exists in different “assemblages" (A through H):
- Assemblages A and B can infect multiple species, including animals and humans.
- Other assemblages are species-specific (e.g., C/D in dogs, E in livestock, F in cats).
- The total number of
Giardia strains and host-infectivity is unknown.
Transmission from animals to humans appears to be rare (human infections primarily come from other humans); nevertheless, some
Giardia parasites may be shared and should be considered potentially zoonotic.
Clinical Signs in Animals
Giardia parasites can damage the intestinal lining, cause abdominal discomfort, and interfere with digestion and absorption. Clinical signs in animals, especially young ones, may include:
- Abdominal discomfort, intestinal gas, weight loss, poor growth or coat condition.
- Soft stools or foul-smelling diarrhea, possibly with mucus.
- Stool is often light-colored and greasy, containing undigested fat (steatorrhea).
- Asymptomatic infection is possible and common in adult animals.
How it Spreads
Giardia organisms are shed in the feces of infected animals and people and transmission occurs via ingestion of infective
Giardia cysts. Hardy
Giardia cysts are immediately infectious and can survive for weeks to months in the environment, especially in cool, damp conditions.
Giardia can be found in or on soil, food, water, and surfaces contaminated with feces from infected animals or humans. Spread happens through:
- Direct contact with infected feces.
- Contaminated water, food, and other surfaces (including contaminated animal).
How it is Diagnosed
Diagnosis usually involves identifying
Giardia cysts or antigens in fecal samples. If you are concerned about possible giardiasis in your animal(s), contact your local veterinarian.
How to Prevent & Control
- Keep pets and livestock away from unsafe water sources
- For livestock and kennels: ensure good environmental management, reduce crowding, and isolate infected animals
- Practice strict hygiene, especially if known infected animals:
- Remove feces daily and dispose of properly
- Bathe pets, especially dogs and cats, to remove cysts
- Clean and sanitize bedding, bowls, and areas with quaternary ammonium disinfectants, steam, or boiling water
-
Giardia Cysts are vulnerable to drying and sunlight—let surfaces dry thoroughly
- For humans: avoid drinking untreated water, practice good hand hygiene, especially around young children or animals
Veterinarians must report* confirmed cases of Giardia in animals:
Giardia is a monitored disease in Oregon, and veterinarians must report cases within 15 days of laboratory confirmation (including in-house testing) using the online fillable reporting form or the Oregon Monitored Disease Reporting Form (pdf).
*Automatic reporting by diagnostic laboratories directly to ODA may fulfil a veterinarian's reporting requirement, but it is the veterinarian's responsibility to confirm that the laboratory reports the disease. Currently both IDEXX and Antech reference laboratories automatically report positive Giardia test results to ODA (see
Searchable Disease List).
If you are concerned about possible human cases contact your healthcare provider
Giardia Cases in Oregon Animals
Reported cases of positive
Giardia tests in animals are included in the table below.
Resources
ODA Resources
Other State Resources
- OHA: Giardiasis
Oregon Health Authority (OHA) information page on giardiasis.
Other Resources