Giardiasis, Dogs, Cats & People
Giardia is a tiny parasite that lives in the intestines of various animals.
Giardia Cyst Trophozoite
Giardia is passed in the feces of animals in the form of a cyst that is resistant to many environmental extremes.
These cysts are scattered through the environment in feces or fecal-contaminated water. These cysts are infectious
when passed, and upon ingestion by the next host, the encysted trophozoites emerge from the cysts in the intestinal
tract. Within the intestine, the trophozoites feed and multiply. Some trophozoites will then form a cyst wall around
themselves, and those cysts will be passed in the feces to continue the cycle.
How Do Dogs, Cats, and People Become Infected?
People and pets rarely share each other’s Giardia
People are typically infected with a human form of Giardia, dogs with a canine form, cats with a feline form, and cattle
and sheep with a ruminant form. People are occasionally infected with a different form that is shared with animals. On
rare occasions dogs and cats have been found infected with the human form. Thus, there is little evidence for direct
transmission from pet dogs and cats to people. However, the rare occurrence of the human forms in cats and dogs
means that there may be a slight chance that they pose a risk as a source of human infection.
To be able to distinguish the specific forms, the veterinarian is required to submit samples for specialized tests.
Symptoms of Infection
In dogs and cats, infection with Giardia is usually asymptomatic. Some pets will, however, develop persistent diarrhea. There is usually no blood in the stool.
In people, infection with Giardia also is often asymptomatic. However, some people can develop acute, intermittent, or chronic nonbloody diarrhea. Other symptoms in people include abdominal cramping, nausea, vomiting, loss of appetite, and weight loss.
Prevention and Treatment
- Unlike for heartworm disease, there are no drugs that can be routinely given to a pet that will prevent infection.
- Dogs, cats, and people that have symptoms of the infection can be treated; however, there are situations where it is difficult to clear an animal of their infections.
- There are approved drugs for treating the infection in people. These drugs have not been approved for this specific use in dogs and cats, but these and similar drugs are used in them.
Risk Factors for Human Infection
- Accidentally swallowing Giardia cysts from surfaces contaminated with feces, such as bathroom fixtures,changing tables, diaper pails, or toys contaminated with feces.
- Drinking water from contaminated sources (e.g., lakes, streams, shallow [less than 50 feet]or poorly maintained wells).
- Swallowing recreational water contaminated with cysts. Recreational water includes water in swimming pools, water parks, hot tubs or spas, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with feces or sewage.
- Eating contaminated uncooked, fresh produce.
- Having contact with someone who is infected with Giardiasis.
- Changing diapers of children with Giardiasis
- Traveling to countries where Giardiasis is common and being exposed to the parasite as described above.
The Companion Animal Parasite Council
The Companion Animal Parasite Council (CAPC) is an independent council of veterinarians and other heath care
professionals established to create guidelines for the optimal control of internal and external parasites that threaten
the health of pets and people. It brings together broad expertise in pararsitology, internal medicine, human health
care, public health, veterinary law, private practice and association leadership.