What is Giardiasis?

Giardiasis is an infection of the digestive system by a microscopic parasite called Giardia lamblia. The giardia organism inhabits the digestive 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. Giardia is suspected to be zoonotic — communicable between humans and animals. Major reservoir hosts include beavers, dogs, cats, horses, humans, cattle and birds.

Symptoms include loss of appetite, fever, explosive diarrhea, hematuria (blood in urine), loose or watery stool, stomach cramps, upset stomach, projectile vomiting (uncommon), bloating, flatulence, and burping (often sulphurous). Symptoms typically begin 1–2 weeks after infection and may wane and reappear cyclically. Symptoms are caused by 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. Untreated, symptoms may last for six weeks or longer.