What is it?
Giardia lamblia (also known as Giardia duodenalis or intestinalis) is a parasitic infection  that causes diarrhea. Giardia is transmitted through water, food or fecal-oral transmission from an infected person.

Who gets it?
This infection occurs worldwide. It is more common in areas with poor sanitation or inadequate water treatment facilities. Overall, it is one of the most common parasites that infect the gastrointestinal (GI) tract and around 20,000 Americans are infected each year.

People at higher risk include:

  • Infants
  • Young children (The highest rates of infection occur in kids under 5)
  • People adopted from an international country
  • Travelers- including international travel and hikers in the wilderness who drink water that has not been adequately treated.
  • Immunocompromised people
  • People with cystic fibrosis
  • People with low levels of stomach acid

Humans are not the only ones affected. Other mammals including dogs, cattle and sheep also can be infected. It appears that there are differences between Giardia found in dogs and humans and transmission of disease between the two is very rare.

Why does it happen?
The parasite lives in water, soil and food. It can also be found on surfaces that may have come
in contact with infected human or animal waste. It can causes infection when a person comes in
contact with it.

Infection is possibly through:

  • Contaminated water. Water is a major source of infection and the cysts survive well in mountain streams. The water needs to filtered, treated or boiled to kill or remove the parasite. Giardia is resistant to chlorination. Deep well water is typically safe because of the filtration of water through the soil.
  • Eating raw or undercooked food which has been contaminated
  • Exposure from another infected person

What are the symptoms?
The symptoms are variable based on the person; about half of people who have been exposed will have no symptoms whatsoever, and will clear the infection. 5-15% of people exposed will have no symptoms, but will shed cysts. This shedding can last for over 6 months. The final 35- 45% have symptoms. Symptoms typically develop after 7-14 days (though development has been documented anywhere between 1-45 days). Symptoms may last 2-4 weeks and can include:

  • Diarrhea
  • Malaise
  • Foul smelling, fatty stools
  • Abdominal cramps
  • Bloating
  • Flatulence
  • Nausea
  • Weight loss- this can be significant, up to 10% of body weight
  • Vomiting
  • Fever

Chronic infection can follow this acute symptomatic period or sometimes occurs in asymptomatic people. Chronic symptoms sometimes can be present, including the symptoms listed above and audible bowel noises, burping and depression. Also, lactose intolerance can develop in up to 40% of infected people. The symptoms of chronic infection can be present in variable severity over many months.

How is it diagnosed?
A stool sample will be taken. Giardia is excreted intermittently; typically at least three specimens are examined. Interestingly, barium, antacids and mineral oil can interfere with a microscopy exam. There are also immunoassays that can be performed. These tests look for antibodies (proteins made by the immune system) against the Giardia. If the first two mentioned tests do not lead to a diagnosis but there is still concern, a duodenal biopsy, a tissue sample of the first portion of the small intestine can be obtained during an upper endoscopy, a procedure where a lighted tube is passed from the mouth to the stomach to the first portion of the small intestine.

How is it treated?

  • If there are no to mild symptoms no treatment is necessary. Many infections will go away on their own in 2-4 weeks.
  • It is important that you stay adequately hydrated and any electrolyte abnormalities will be corrected.
  • You may be treated with medications to clear the infection if the symptoms are severe, do not go away on their own, or are at risk for spreading the infection to others (for example working in a day care center or nursing home).

For at least one month after treatment you should avoid dairy products often a self-limited lactose intolerance develops with the infection.

What are the complications?
Dehydration, malabsorption and weight loss. Rarely reactions such and rash, hives (urticaria), canker sores (aphtous ulceration) and joint pains can occur. Infrequently Giardia can spread to the biliary and pancreatitic ducts, the tubes leading from the gallbladder, liver and pancreas into the small intestine, this can cause inflammation of the these organs.

What can I do?
As discussed, Giardia is spread in three ways; all these ways can be prevented.

Water. This is the most common way people are infected.
To avoid infection:

  • Do not drink from a contaminated stream, water reservoir or well.
  • Do not prepare drinks or wash food from a contaminated or possibly contaminated water source.
  • When camping do not drink from any untreated water source.
  • When travelling be mindful of where your water is coming from, especially in areas where there not be adequate water sanitation standards.
  • Avoid swallowing water when swimming. This is not just in lakes; remember Giardia is resistant to chlorine!

This organism is killed by cooking so make sure that your food is properly cooked. Be aware that food can be contaminated after cooking. Wash your hands with soap and water before eating.

This occurs when infected stool passes between two people. There are several settings that this can occur so be sure to wash hand thoroughly after passing a bowel movement, changing a child’s diaper or tending to a person with poor bowel control. Make sure to dispose of diapers properly. Know that unprotected anal sex can also lead to transmission. Person-to-person is usually the source of transmission when there is an outbreak within a family, day care center or nursing home.

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