Giardiasis is a diarrheal illness caused by a one-celled, microscopic parasite, Giardia intestinalis (also known as Giardia lamblia). Once an animal or person has been infected with Giardia intestinalis, the parasite lives in the intestine and is passed in the stool. Because the parasite is protected by an outer shell, it can survive outside the body and in the environment for long periods of time.

During the past 2 decades, Giardiainfection has become recognized as one of the most common causes of waterborne disease (found in both drinking and recreational water) in humans in the United States . Giardia are found worldwide and within every region of the United States.

Causes

The Giardia parasite lives in the intestine of infected humans or animals. Millions of germs can be released in a bowel movement from an infected human or animal. Giardia is found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals. You can become infected after accidentally swallowing the parasite; you cannot become infected through contact with blood. Giardia can be spread by:

• Accidentally putting something into your mouth or swallowing something that has come into contact with feces of a person or animal infected with Giardia.
• Swallowing recreational water contaminated with Giardia. Recreational water includes water in swimming pools, hot tubs, jacuzzis, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with sewage or feces from humans or animals.
• Eating uncooked food contaminated with Giardia.
• Accidentally swallowing Giardia picked up from surfaces (such as bathroom fixtures, changing tables, diaper pails, or toys) contaminated with feces from an infected person.

Risk Factors

A risk factor is something that increases your chances of getting a disease or condition.

• Age group: Young children and elderly adults

• Unsanitary or crowed living conditions

• Drinking untreated water, such as:

• • Well water

• • Stream or lake water

• Low stomach acid, often found in:

• • Elderly people

• • People on ulcer drugs

• Oral-anal sex

• An impaired immune system

• Working or staying in a daycare center or nursing home

• International travelers

• Hikers, campers, and swimmers

Symptoms

Symptoms usually start 5-28 days after infection. Not all people who are infected have symptoms. But, all people who are infected can transmit the disease.

Symptoms may include:

• Diarrhea, acute or chronic

• Loose, greasy, foul smelling stools

• Abdominal pain or cramps

• Bloating

• Gas

• Nausea or vomiting

• Weight loss

• Mild fever (rare)

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam. Tests may include:

• Laboratory exam of several (usually three) stool samples

• Stool testing for Giardia proteins (called the Giardia antigen test)

• In some cases, testing of a fluid or tissue sample from the intestine

If you are diagnosed with giardiasis, everyone living in your household should be tested for infection as well.

Treatment

Giardiasis is treated with a prescription antiparasitic drug. Although Giardia can infect all people, young children and pregnant women may be more susceptible to dehydration resulting from diarrhea and should, therefore, drink plenty of fluids while ill. The medication is usually given for 5-10 days and may be one of the following:

• Metronidazole

• Furazolidone

• Paromomycin

• Quinacrine

• Nitazoxanide

• Tinidazole

Giardia may be resistant to any of these medications or to several others occasionally used. Resistance may complicate treatment and prolong illness.

Prevention

To prevent getting or spreading giardiasis:

• Maintain good personal hygiene

• Wash hands several times a day, especially:

• • Before eating or preparing food

• • After a bowel movement

• • After changing a diaper

• When camping:

• • Bring bottled water for drinking, cooking, and brushing teeth

• • Purify untreated water before using; boil, filter, or otherwise sterilize

• Thoroughly wash or peel raw fruits and vegetables before eating

• When traveling overseas:

• • Use only bottled water for drinking, cooking, or brushing teeth

• • Only eat food that is adequately cooked and served steaming hot

• Do not let children with diarrhea go into swimming pools

• Keep swimming pools adequately chlorinated

• Stay home from work and keep children home from school or daycare until the infection is gone

RESOURCES:

The American Academy of Family Physicians
http://www.familydoctor.org

Maryland Department of Health and Mental Hygiene
http://www.dhmh.state.md.us/

Massachusetts Department of Public Health, Bureau of Communicable Disease Control
http://www.state.ma.us/dph/cdc

References:

American Academy of Family Physicians website. Available at: http://www.familydoctor.org.

Harrison's Principles of Internal Medicine, 15th ed. McGraw-Hill Professional Publishing; 2001.

Massachusetts Department of Public Health, Bureau of Communicable Disease Control website. Available at: http://www.state.ma.us/dph/cdc.

The Merck Manual of Medical Information. Simon and Schuster, Inc.; 2000.