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Giardiasis
What is Giardiasis?
Giardiasis is an intestinal illness caused by infection with a parasite called Giardia lamblia. The infective form is called a cyst, a stage in the parasite's life cycle which allows it to survive in the environment, primarily fecally contaminated water. Infection is acquired by swallowing cysts. Upon reaching the intestine, the cyst transforms into the second stage of the parasite's life cycle, which is called a trophozoite. The trophozoite stage of Giardia grows and multiplies in the intestine, and is responsible for the symptoms of the illness. The trophozoite stage is also capable of forming cysts, which are passed from the body in the stool (bowel movement). Giardia lamblia parasitizes humans as well as other mammals, such as beavers, thus one of the many common names once used for giardiasis was "Beaver Fever".
Who gets Giardiasis?
Anyone can get giardiasis, but it is more frequently found in persons living in institutional settings for the developmentally disabled, individuals in child care settings, and travelers to areas with poor sanitation. Anyone who drinks untreated surface water, such as water taken directly from ponds, lakes and streams, is at increased risk of acquiring giardiasis. Transmission of giardiasis has also been documented in male homosexuals. Pets may also harbor Giardia.
How is Giardiasis spread?
A person becomes infected with Giardia by swallowing cysts of the parasite. This can occur when an individual eats or drinks food or water contaminated with Giardia cysts, or through direct contact with an individual infected with Giardia who has poor personal hygiene.
What are the symptoms of Giardiasis?
The most common symptoms of Giardiasis include diarrhea, abdominal cramps, pale and greasy stools, fatigue, bloating, and weight loss. Fever is usually absent. Many persons with Giardia have no symptoms at all.
How soon do symptoms occur?
Symptoms may begin 3 to 25 days after swallowing Giardia cysts, but usually within 10 days.
How is Giardiasis diagnosed?
Giardiasis is typically diagnosed by finding Giardia lamblia cysts in a stool sample submitted to a laboratory. Since cysts are intermittently passed in the stool, more than one specimen may be necessary to make the diagnosis because the cysts may not be in every stool specimen.
What is the treatment for Giardiasis?
Some individuals recover from giardiasis without any treatment. When therapy is necessary, antibiotics are often prescribed. The drugs currently used to treat giardiasis are effective in most but not all individuals, and relapses do occur.
How long is an infected person infectious to others?
An infected person is capable of transmitting giardiasis to others as long as Giardia cysts are being passed in the stool (bowel movement). This may last from a few weeks to months.
Should an infected person be excluded from work or school?
Anyone with diarrhea should remain home from work or school to minimize the risk of passing this infection on to others. In most cases, individuals may resume routine activities after the symptoms of illness have resolved. However, cysts will continue to be passed in the stool for up to several months after the symptoms have resolved, so it is important that the individual practices good personal hygiene, including washing his/her hands after using the toilet.
Special precautions are indicated for food handlers, health care workers, and day-care providers. Food handlers should be excluded from direct contact with food until they have completed a course of antibiotic therapy and no longer pass cysts in their stool. Health-care workers may return to direct patient care activities when their symptoms of illness have resolved, provided they have good personal hygiene. Child care workers infected with Giardia should not handle or prepare food. Consult your local health department for further advice in these circumstances.
How can Giardiasis be prevented?
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