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Articles Home > Dog Health > Giardia


Posted: 3/26/2011 | Updated: 3/26/2011


What is Giardia?

Giardia are single-celled organisms that can live in the small intestines of dogs, cats and other mammals. Giardiasis is an infection of Giardia. Giardia can interfere with digestion, prevent the proper absorption of nutrients and damage the delicate lining of the intestine. It is estimated that 5% to 10% of dogs in the United States are affected at any given time.

What are the Signs of Giardiasis?

Typically there are no symptoms but diarrhea, weight loss, inability to maintain a healthy weight especially during growth, vomiting and lack of appetite may occur. The feces of an infected animal may appear abnormal; having a pale color, greasy appearance or an unusually bad odor.

How is Giardia Transmitted?

A dog becomes infected by eating a cyst of the parasite. Once the cyst makes its way into the small intestine, it opens and releases a trophozoite. The trophozoites attach themselves to the wall of the intestine and begin multiplying. There is a lot that is still unknown about this process, but at some point during this reproduction stage the Giardia form a wall around themselves or encyst. It is the cysts that are passed in the feces of an infected animal and can be transmitted to other animals or possibly humans. There are many strains of Giardia, some that do indeed infect humans. It is still unknown if people can catch it directly from a dog's feces.

How is Giardiasis Diagnosed?

Giardiasis is very difficult to diagnose because Giardia are very tiny and are not passed with every stool. Typically, a stool sample must be tested every day for 3 or 4 days for Giardia to be diagnosed.

How is Giardiasis Treated?

This is a controversial topic as well. Because it is not know whether Giardia found in dogs can directly affect humans, typically vets error on the side of caution and treat any case whether the animals is displaying symptoms or not. If a dog has diarrhea and no other cause can be found, Giardiasis is often suspected and treated.

Antiparasitic drugs such as Fenbendazole or Metronidazole are often prescribed. Fenbendazole is used to kill intestinal worms and helps to control Giardia. Metronidazole can also kill other types of bacteria that cause diarrhea. Neither are 100% effective and have health drawbacks including liver damage. The effect on a developing embryo is unknown so they should never be used in pregnant animals. Quinacrine hydrochloride has been used previously but has been proven less than effective and has a range of harmful side effects including lethargy, vomiting, anorexia, and fever. Despite these treatments it is still not known if they actually eliminate the Giardia or just eliminate the cysts that the tests check for. It is entirely possible that the fecal test come back normal but the dog still be infected with Giardia.

How Can I Prevent Giardia?

The infectious cysts can live months in cool, wet environments including puddles, lawns, kennels, parks, etc. Keeping your dog away from such areas is the only real prevention. Making sure they do not drink from puddles or other standing water is very important. Cleaning with Lysol and diluted bleach are known to kill the parasite.

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