Giardia infection (giardiasis) is an intestinal infection caused by microscopic parasites that are found especially in areas with poor sanitation and contaminated water. Giardia infection is characterized by abdominal cramps, bloating, nausea and bouts of watery diarrhea.

Giardia infection is a waterborne infection from parasites that can be found in municipal water supplies, swimming pools, spas and backcountry streams and lakes. It can also be spread through food or human contact.

Recovery from giardia infections usually takes several weeks; however, a longer period of intestinal problems may be the consequence of the parasites.



Symptoms of giardia infection include:


  • Watery, sometimes foul-smelling diarrhea
  • Fatigue or malaise
  • Abdominal cramps and bloating
  • Belching gas with a bad taste
  • Nausea
  • Weight loss



Giardia parasites live in the intestines of people and animals. They are passed in stool and survive until they find a new host. Infection occurs when the parasites are ingested. This can occur by swallowing or drinking contaminated water, eating contaminated food or through person-to-person contact.


  • Swallowing contaminated water: giardia parasites are present in lakes, pounds, rivers, streams as well as municipal water supplies, wells, swimming pools, parks and spas.
  • Eating contaminated food: the food may contain giardia parasites if the handlers have giardiasis and have not washed their hands properly or because the raw produce is irrigated or washed with contaminated water.
  • Person-to-person contact: if the hands become contaminated with fecal matter one may contract giardiasis. Another way of spreading the disease is anal sex.


Risk factors

Risk factors for giardia parasites or infection include:


  • Being a child: children are more likely to come in contact with feces, especially while wearing diapers or spend time in a childcare center.
  • Drinking contaminated water: places with poor sanitation or contaminated water are the perfect home for giardiasis.
  • Anal sex: unprotected anal sex increases the risk of giardia infection



The common complications of giardia infection include:


  • Dehydration: dehydration may be the result of severe diarrhea
  • Failure to thrive: chronic diarrhea may lead to malnutrition and be damaging to children’s physical and mental development
  • Lactose intolerance: giardia infection may cause the development of lactose intolerance, which may persist after the infection has cleared



The following precautions may help prevent giardia infection:


  • Washing hands: this is especially important after using the toilet, changing diapers or before eating or preparing food
  • Purifying wilderness water
  • Avoid swallowing water when swimming in pools, lakes or streams
  • Using bottled water, especially when travelling to parts of the world where water supply is unsafe
  • Practicing safe sex