Giardia lamblia is an infection of the small intestine. It is contracted when a person puts something in their mouth that has been in contact with Giardia lamblia. This most frequently includes contaminated water, (swimming pools, hot tubs, lakes or rivers) though a person can also be infected by putting their mouth on toys or raw foods.
Different individuals with the same strain of Giardia lamblia render a variety of symptoms throughout the course of the disease. Such symptoms frequently include: diarrhea, loose or watery stool, stomach cramps, and lactose intolerance. Rare infections include disaccharide intolerance. These symptoms begin one to two weeks after infection and may lead to weight loss and dehydration. Effects of Giardia lamblia persist for two to six weeks, though some people experience no symptoms upon infection.
Many adults have a lasting immunity to the infection, but children remain quite susceptible. The overall incidence of infection in the United States is approximately two percent of the population.
More Information on Giardia lamblia:
Giardiasis - Centers for Disease Control and Prevention (CDC)