Giardia? What is it and Why Can’t My Pet Get Rid of it???

One of the most pesky “bugs” we deal with as veterinarians is a one-celled parasite called Giardia This probably sounds familiar to you as it’s one of the most common causes of diarrhea in cats and dogs.   It lives inside the intestines as one form called a trophozoite.  Outside the body the trophozoites band together and form a “cyst,” which is found in fecal material.

Animals typically become infected by ingestion of infected fecal material.  One of the most common modes of transmission is contaminated water.  So if your pet is drinking from a puddle in the park, there is a good chance they can swallow the cysts.  There are also some dogs out there guilty of periodic “stool-eating” (we don’t know what the appeal is) that can ingest it in that manner as well.   What also makes this parasite even more of a nuisance is the cysts in the fecal material can actually stick to your pet’s coat.  So if an animal is cleaning himself and happens to ingest fecal material while doing so, he can actually re-infect himself with the parasite.  This can become a problem with animals in close quarters particularly in a dog park or day care situation where these little guys are in constant contact with one another.

If your pet is already infected with Giardia and is being treated, hygiene is a major factor in controlling re-infection.  So after your pet has a bowel movement ,  if you notice there is fecal material stuck to the coat, make sure to clean it off.

Giardia is actually considered a zoonotic organism, meaning humans can get it.   However, it is rare that a person would actually get Giardia from a dog or cat since they would have to ingest the feces of an animal infected with it.   A far more common source of infection would be contaminated water sources.  Campers and hikers are at risk if they drink untreated water from lakes and streams.  We do see some infections in immunocompromised individuals or those that work in nursing homes and long term care homes.

Your veterinarian may test for Giardia by taking a fecal sample and examining it under the microscope in the hospital or sending it out to a separate laboratory.  Giardia doesn’t always cause diarrhea, this is why it’s important to have your pet’s stool tested once a year even if it’s not sick.

This information should not steer you away from all the activities your pet loves, such as day care, dog parks, and any other outdoor activity because the prognosis for Giardia is good.  The actual parasite is pretty wimpy, so medication will take care of it.  We typically use a dewormer called Panacur that goes in the food and an antibiotic called Metronidazole.  This is the most common and effective treatment.

The best thing you can do as a pet owner is pick up your pet’s feces after they have a bowel movement and avoid walking them in areas riddled with other animal’s fecal material.  Also, try to stop them from drinking out of puddles, ponds, or any stagnant water source.  Additionally, bring your pet’s feces in for a parasite check yearly to test for feces.  Giardia can be rather troublesome for veterinarians, but as diligent and informed pet owners, you can prevent an infection.


Dr. Julie Jones

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West Village Veterinary Hospital