giardiasis

Giardiasis is an infection of the small intestine caused by a microscopic parasite called Giardia intestinalis. It is one of the most common waterborne diseases in the United States and globally affects millions each year. The name "beaver fever" comes from the fact that beavers often carry Giardia and can contaminate waterways with it—though humans aren't usually infected by beavers directly!

The parasite exists as a cyst (a protective shell) in water or food contaminated with fecal matter. When ingested, these cysts transform into active parasites that attach to the intestinal wall, disrupting digestion and causing symptoms like diarrhea (often greasy and foul-smelling), abdominal cramps, bloating, nausea, and dehydration. Symptoms can last for weeks or even months if left untreated.

Giardiasis is commonly contracted by drinking contaminated water—from streams, lakes, or improperly treated sources—but it can also spread through contaminated food, especially raw produce, or through close contact with infected individuals (like in daycare centers).

Fortunately, giardiasis is usually treatable with prescription medicine. Prevention is key: always purify water when hiking or camping, practice good hygiene (especially handwashing), and be mindful of food safety. While unpleasant, most cases clear up completely with treatment, leaving you free to enjoy those mountain streams—after properly filtering the water, of course.