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How Giardia Affects Your Pet

Giardia: How it Affects your Pet.

Dr. Leanne Donovan

Most people who own a pet know that a fecal sample examination is part of any yearly check up for their dog or cat. They are aware that there are certain intestinal worms this test screens for which can affect their pet's well being. However, not all intestinal parasites are worms, and among this group of other disease-causing organisms is Giardia, a common and important parasite of not only dogs and cats, but occasionally people as well.

Here at Dover Veterinary Hospital, we diagnose and treat cases of Giardia, primarily in dogs, but also in cats, on a weekly basis. With many pets having an active lifestyle: hiking, swimming, and camping with their families, in addition to more dogs having a substantial travel history (we see many rescued dogs these days which have come from southern states) and increased exposure to one another with the advent and meteoric rise of doggie daycare, we find that Giardia is constantly on the list of potential causes of diarrhea in our patients.

What is Giardia? (From VeterinaryPartner.com)

Giardia is the genus of a protozoan parasite that is infectious to both humans and pets all over the world. Giardia consists of flagellates, which mean they move by means of several whip-like structures called flagella. They live as a form called a trophozoite, or "troph" for short, in the intestine where they cause diarrhea. In fresh fecal samples, trophozoites can sometimes be captured.
After a short period of time outside the host's intestine, the trophozoites round up and form cysts, which enable them to survive environmental conditions without a host to protect them. The cyst can live for many months with two incompletely formed trophozoites inside, ready to infect a new host. Contaminated water is the classical source of a Giardia infection.

How is Giardia transmitted?

Contaminated surface water is the most likely source of infection, including lakes, streams, and ponds. Wildlife are a natural reservoir for the organism, and the nickname Beaver Fever refers to the fact that beavers are a common source of water contamination. Once a dog or cat drinks from a contaminated source, the Giardia cysts enter their digestive tract, releasing the infective trophozoites to affect the intestines.

This is the same for people. According to the Center for Disease Control, several of the most common ways that people are infected are:

Travelers to countries where giardiasis is common
People in child care settings
Those who are in close contact with someone who has the disease
People who swallow contaminated drinking water
Backpackers or campers who drink untreated water from lakes or rivers
People who have contact with animals who have the disease

Several years ago clients of mine had taken their family and two Labradors hiking in the White Mountains, where they all drank unfiltered stream water. All four family members and both dogs had to be treated for Giardia the following week.

In dogs and cats, symptoms of Giardia infection or Giardiasis appear typically 5- 12 days after being infected. In people signs can take 1-3 weeks to manifest after infection. The major symptom in dogs and cats is diarrhea, often with a strong, fetid odor. This diarrhea may be intermittent or continuous, depending on the individual. Occasionally we do see dogs that have mild vomiting, especially early on. People likewise experience diarrhea, cramping, and possible nausea and vomiting.

Diagnosis of Giardia

Giardia is often suspected based on the potential exposure history of the pet or person involved (i.e. a dog who often goes to a dog park where many dogs congregate, or a person who has drunk unfiltered water while hiking) and is relatively easy these days to test for. When a patient at our hospital exhibits diarrhea that lasts for more than a day or two, we often test for Giardia. This typically involves an in-house test kit (Giardia Snap ELISA test) which gives results in under ten minutes. We make it a point to routinely test new pet additions to a household, including pets adopted from shelters and transported from rescue groups out of state, and are often able to confirm infection before the pet becomes ill.

Treatment of Giardia

Fortunately, Giardia infection (Giardiasis) is relatively easy to treat in our patients. A typical patient is often placed on a bland, easy to digest diet that produces little waste such as Iams Low Residue or Hill's I/D food, and is prescribed either of two common medications: fenbendazole or metronidazole. Which medication is prescribed depends on the age and size of the patient, as well as whether or not the patient is pregnant or nursing. Most simple cases show rapid improvement within a few days, however, more severe cases may require a longer course of prescription diet for healing intestines as well as the addition of a probiotic to speed recovery.

One of the steps of treatment which we emphasize is good hygiene once a pet has been diagnosed with Giardiasis. Keeping fecal matter promptly cleaned up in the environment of an infected dog, as well as keeping the litter changed frequently in the litter box of an infected cat is an important step in control. Disinfecting runs, cages, carriers and crates that pets have been in can decrease the risk of re-infection. Bathing the affected pet at the end of a course of medication to treat Giardiasis can remove cysts that may cling to fur and have the ability to infect the same or other pets. Proper hand washing after any contact with potentially contaminated surfaces or fecal matter is essential.

From the Merck Veterinary Manual:

Giardia cysts are immediately infective when passed in the feces and survive in the environment. Cysts are a source of infection and reinfection for animals, particularly those in crowded conditions (eg, kennels and catteries). Prompt removal of feces from cages, runs, and yards limits environmental contamination. Cysts are inactivated by most quaternary ammonium compounds, household bleach (1:32 or 1:16 dilution), steam, and boiling water.

To increase the efficacy of disinfectants, solutions should be left for 5-20 min before being rinsed off kennel or run surfaces. Disinfection of grass yards or runs is impossible. These areas should be considered contaminated for at least a month after infected dogs last had access. Cysts are susceptible to desiccation, and areas should be allowed to dry thoroughly after cleaning. Cysts contaminating the hair of dogs and cats may be a source of re-infection. Shampooing and rinsing the animals well can help remove cysts from hair.

Our goal is to prevent, diagnose, and treat symptoms from Giardiasis as soon as possible in our patients, but also to try to ensure that they don't become infected again or possibly infect their human family members. While most commonly humans and pets in the same household with Giardia have been exposed to a common source, it is occasionally possible for Giardia to be passed from pets to people. With so many of our patients going to dog parks, daycare, traveling, and visiting boarding and grooming facilities, we now check for Giardia along with other intestinal parasites with our Canine Annual Wellness Panel in order to catch more cases early, and to protect other household members, canine, feline, and human.
If you have any questions about Giardia and your pet, please call us and we will be happy to answer them for you.

Further Reading



CDC (Center for Disease Control) on Giardia

CAPC (Companion Animal Parasite Council)Information on Giardia and other intestinal parasites.

More on SNAP testing technology

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