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Giardiasis (cont.)

Giardia: How Can You Prevent Giardiasis?

  • Avoid contaminated water
    • Travelers to developing countries and hikers in the wilderness should consider all water sources contaminated. For travel to high-risk areas (Africa, Latin America, southern Asia), where medical care may not be readily available, talk to your doctor about taking prescription medication with you. Over 80% of diarrhea in travelers is caused by bacteria and is usually treated with a quinolone antibiotic. Diarrhea that does not go away with a quinolone antibiotic may be caused by a parasite such as Giardia lamblia and can be treated with metronidazole. Any diarrheal illness that does not include fever or bloody diarrhea can be relieved with Imodium or Pepto-Bismol as directed, as long as the antibiotic is also taken.
    • All water must be boiled, filtered, or treated with halogenated tablets or solutions (chlorine-type treatment to purify).
    • Avoid foods washed in contaminated water or that cannot be cooked or peeled. Travelers to foreign countries should be especially careful to avoid drinking water in foreign countries (including ice cubes in drinks). Drink bottled water. Avoid fresh fruits and vegetables that may have been washed in contaminated water. Eat only items that can be peeled.
    • In the United States, many reported cases of Giardia lamblia occur in the summer months. This may be due to the use of community swimming areas by young diaper-aged children (such as lakes, pools, and water parks.)
  • Avoid risky sexual behaviors.
  • Wash hands thoroughly with soap and warm water after using the bathroom and before eating.
  • Wash hands after changing a baby's diaper. If you are a daycare worker, it is especially important to wash after changing each child.

Giardia: What Is the Prognosis for Giardiasis?

Cure rates are high with appropriate medication in an otherwise healthy person. Treatment failure may be due to poor compliance with medication, reinfection, resistant strain, or underlying difficulty with the immune system. Resistant strains may require a second course of the same medication or a change to a different medication.

  • Giardiasis may lead to lactose intolerance during the infection and up to several weeks after treatment. Symptoms of lactose intolerance, which include bloating, cramping, and watery diarrhea after ingestion of milk products, may be misinterpreted as reinfection.
  • In someone with a weakened immune system, giardiasis may lead to chronic infection. Chronic infection is associated with difficulty absorbing some important vitamins, minerals, and protein that may lead to malnutrition. Malnutrition in infants and young children may lead to impairment of growth and development.

Medically reviewed by Robert Cox, MD; American Board of Internal Medicine with subspecialty in Infectious Disease


Nazer, Hisham, MB, BCh, FRCP, DTM&H. "Giardiasis." Medscape. Updated Feb 15, 2016.

Medically Reviewed by a Doctor on 10/26/2016

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Giardiasis »

Giardia lamblia was originally identified by von Leeuwenhoek in the 1600s and was first recognized in human stool byVilem Dusan Lambl (1824-1895) in 1859and by Alfred Giard (1846-1908) after whom it is named.

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