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Tropical Diseases

Giardiasis: A One-Celled Wonder

Giardia is a one-celled, microscopic parasite that lives in the intestines of people and animals and is passed in the stool of an infected person or animal. It is protected by an outer shell, which helps it survive outside the body and in the environment for long periods of time. During the past 20 years, giardia has been recognized as one of the most common causes of waterborne disease in the United States.

The giardia parasite causes a disease called giardiasis, which results in diarrhea, belching, gas, and cramps. The disease is easy to catch if you drink untreated spring water or water from a stream. Many animals carry giardia in their feces and may introduce it into rivers, streams, and springs. Infected water may look clean and safe even if it isn't. City water supplies can get infected if sewer lines rust or leak. It is also possible to get the disease from drinking water in certain countries if that water hasn't been boiled or treated.

Symptoms usually develop one to two weeks after infection, and they last two to six weeks.

Antigen Alert

Everyone is at risk for giardiasis, which is a highly contagious disease.

How Does It Spread?

Giardia lives in the intestines of infected people and animals. Millions of germs can be excreted in a single bowel movement from a person or animal. The parasite can be found in soil, food, water, or surfaces that have been contaminated with feces from infected people or animals. Infection can happen after accidentally swallowing the parasite.

Giardia is spread by …

  • Putting something in your mouth or accidentally swallowing something that has come in contact with the stool of a person or animal that is infected.
  • Swallowing water that is contaminated. This could be water from a swimming pool, hot tub, Jacuzzi, fountain, lake, river, spring, pond, or stream 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 contaminated with stool from an infected person. Contaminated surfaces could be toys, bathroom fixtures, changing tables, or diaper pails.

Giardiasis is diagnosed by examining a stool sample under a microscope and looking for the presence of the organism. Sometimes several samples have to be taken before the diagnosis can be made.

The disease is usually treated with a medicine called Flagyl, which is typically taken three times a day for 5 to 10 days. Side effects include nausea and a metallic taste in the mouth. You shouldn't drink alcohol while taking the medicine, and it shouldn't be taken in the early stages of pregnancy. Young children are sometimes given a different medicine.

Because the disease is so contagious, sometimes whole families are treated together even if they don't all show symptoms for the disease. The doctor will probably check another stool sample when treatment is finished in order to be sure that the medicine worked. There are situations where a second medication or a longer course of treatment may be necessary.

Potent Fact

According to the CDC, if you are diagnosed with a giardia infection, you can prevent it from spreading through several simple steps:

  • Wash your hands with soap and water after using the bathroom, changing diapers, and before eating or preparing food.
  • Avoid swimming in recreational water for at least two weeks after diarrhea stops (you can still pass the infection after your symptoms have stopped).
  • Avoid fecal exposure during sex.

Wash Those Hands!

Practicing good hygiene is the best way to prevent infection. Wash your hands with soap and water after using the bathroom and before handling or eating food. Wash your hands after every diaper change, especially if you work with young children. Protect others by not swimming if you have diarrhea and not letting your children swim if they have diarrhea.

Another good preventive measure is to avoid water that might be contaminated. Don't swallow water when you are swimming. Don't drink untreated water from wells, lakes, rivers, springs, or ponds. If there is an outbreak in your community, don't drink untreated water. Avoid using ice or drinking untreated water when traveling in countries where the water supply may be unsafe. If you have to drink untreated water, treat it yourself by heating the water to a rolling boil for at least one minute. Avoid food that might be contaminated. Wash and/or peel all raw fruits and vegetables before eating them. Avoid eating uncooked foods in countries with minimal water treatment and sanitation systems.

book cover

Excerpted from The Complete Idiot's Guide to Dangerous Diseases and Epidemics © 2002 by David Perlin, Ph.D., and Ann Cohen. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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