Giardiasis (also known as beaver fever) is a disease caused by the flagellate protozoan Giardia lamblia (also Giardia intestinalis). The giardia organism inhabits the digestinal tract of a wide variety of domestic and wild animal species as well as humans. It is a common cause of gastroenteritis in humans, infecting approximately 200 million people worldwide.
Giardiasis is passed via the fecal-oral route. Primary routes are personal contact and contaminated water and food. People who spend time in institutional or day-care environments are more susceptible, as are travelers and those who consume improperly treated water. It is a particular danger to people hiking or backpacking in wilderness areas worldwide. It is zoonotic -- communicable between animals and humans. Major reservoir hosts include beavers, dogs, cats, horses, and cattle.
Symptoms include loss of appetite, lethargy, diarrhea, loose or watery stool, stomach cramps, upset stomach, bloating and flatulence. Symptoms typically begin 1-2 weeks after infection and may wane and reappear cyclically. Symptoms are caused largely by the thick coating of Giardia organisms coating the inside of the small intestine and blocking nutrient absorption. Most people are asymptomatic; only about a third of infected people exhibit symptoms.
Antibiotics used to treat adults include metronidazole, albenzazole and quinacrine. Furazolidone and nitazoxanide may be used in children. Treatment is not always necessary, as the body can defeat the infection by itself.
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