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Giardia

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image of giardia cyst

Immunofluorescence image of Giardia lamblia cysts, purified from Mongolian gerbil fecal material.

H.D.A. Lindquist, U.S. EPA

What is Giardia?:

Giardia are one-celled organisms found in the small intestines of cats. They undergo two stages: a motile (swimming) stage and a cystic stage (pictured). Giardia cysts are the primary means of transmission from host to host. Giardia cysts are hardy, being resistant to both freezing and to chlorination of water, and can live for several months if not dried out or exposed to sunlight.

How is Giardia Transmitted?:

Giardia cysts are excreted (shed) in the feces of an infected cat, then picked up when ingested by other cats sharing litter boxes. Giardiasis is the name given to the infection. Not all cats infected with giardia will become sick. Cats may host the organism for several years, while passing it on to other cats, before showing any clinical signs of giardiasis. An immune-suppressant factor, such as FIV, FeLV, or overall debilitation, may hasten the onset.

The incidence of feline giardiasis is relatively low in North America (about 4 %), but it can sometimes wreak havoc in catteries, shelters, and some multi-cat households; in short, wherever a large number of cats share space. Also, cats with outdoor access may ingest the organism by drinking water from a stream or pond, particularly in agricultural areas.

What Are Its Symptoms?:

The most common symptom of giardiasis is diarrhea, either with sudden onset, or of the more chronic variety. Stools may be bloody or accompanied by mucous or flatulence, and the cat may lose weight, become listless, and neglect grooming. Since these symptoms may be indicative of a number of other medical conditions, including IBD and cancer, only a veterinarian can make an accurate diagnosis, through examination and tests.

How is Giardia Diagnosed?:

Giardia cysts can be identified in a fecal smear under a microscope. Since cysts are shed in stools sporadically, several different fecal samples may be needed for a positive identification. Special stains may be needed, as the organism can sometimes be elusive.

How is Giardiasis Treated?:

Giardiasis is often treated with metronidazole (Flagyl), but there are several other oral medications available. According to Dr. Mike Richards, cats show more resistance than dogs to medication for giardiasis, so sometimes it takes several courses of treatment or a switch to another medication to effect a cure.

Scrupulous scooping, cleaning, and disinfecting of litter boxes will help prevent the spread of giardia to other cats. A 30:1 solution of chlorine bleach may be effective for litter boxes, and some catteries advocate steam cleaning of all surfaces where giardia cysts might be present.

Can Giardia Spread to Humans?:

There is a human form of giardiasis, but since there are several strains of giardia, it is possible that any given strain might not spread from feline to human. (Human giardiasis is also caused by drinking contaminated well water.) However, to be safe, it makes sense to use good sanitation procedures. Wash your hands thoroughly with soap and water after cleaning litter boxes and before handling food or touching your mouth.

While a diagnosis of giardiasis sometimes strikes terror in the hearts of cattery owners and shelter volunteers, early intervention can help prevent a widespread epidemic.

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