Imagine, if you will, that you are hiking in the wilderness with your family and friends. You come upon a lovely mountain stream, and because of your exhausting hike you decide to take a drink, but before you do so your friend tells you "don't drink the water, you'll get sick!". This statement then makes you wonder, how can I get sick from drinking cool, clear, mountain water. Your friend, being the friend that he is, then begins to enlighten you about a microscopic parasite called giardia (a.k.a. beaver fever).

Giardia lamblia is a single celled parasite that can cause an intestinal illness known as giardiasis. Giardiasis is the single most frequent cause of non-bacterial diarrhea in North America. Giardiasis is most common anywhere there is contamination of surface or domestic water. Cases occur sporadically and/or in clusters or outbreaks. The largest reported outbreak in the USA involved 24 of 36 people who consumed macaroni salad at a picnic. Anyone can contract giardiasis, but it most often occurs in people in institutional settings, people in day care centers, foreign travelers and individuals who consume improperly treated surface water and, in some cases, food. Giardiasis is more prevalent in children than adults. This is because many individuals seem to have a lasting immunity after infection. Although giardiasis is more common in children than adults, the more chronic symptoms are found in adults. The overall infection rate is about 2% in the Unites States. That might not sound like much, but when you consider the  population of the US, it quickly becomes millions.

The symptoms of giardiasis may appear from 5 to 25 days and usually show up in about a week [after infection]. People exposed to giardiasis may experience mild to severe diarrhea, bloating, excessive gas or, in some instances, no symptoms at all. Some individuals will have chronic diarrhea over several weeks or even months, resulting in significant weight loss. About 40% of people infected with giardia demonstrate disaccharide intolerance during detectable infection and up to six months after infection can no longer be detected. Lactose intolerance is most commonly observed. Giardiasis has been known to cause death. The giardiasis parasite is passed in the feces of an infected person or animal. That waste may also contaminate food or water. That is why any untreated source of water can potentially infect a person. Giardia is particularly tenacious in that it only takes one or more cysts to cause the disease, compared to hundreds to thousands of bacterium needed to produce [most] illness[es]. Person to person transmission may occur in day care centers where diapering is done and where hand-washing practices are rarely done. Giardia has been found in infected people with or without symptoms and wild and domestic animals. The beaver has been theorized as the potential source of giardia contamination of lakes, reservoirs, and streams; which brought about the name beaver fever. The disposal of raw human sewage in water ways is also a large contaminating factor in the spread of giardia.

The giardia lamblia parasite is frequently diagnoses by visualizing the organism, either in it's active reproducing form (trophozite) or the resting stage (cyst) in stained preparations or unstained wet mounts with the aid of microscopes, of course. A commercial fluorescent antibody kit is available to stain the organism. Giardia may be concentrated by sedimentation or flotation. These procedures, however, reduce the number of recognizable organisms in the sample. Giardia has some mimic diseases that are very similar to giardia. These mimics are amoebiasis and travelers' diarrhea. Amoebiasis differs from giardia in that amoebiasis often is accompanied with bloody stool. Travelers' diarrhea differs from giardia because travelers' diarrhea has fevers and is often [the] shorter sickness.

The treatment for giardia is usually antibiotics such as atabrine, metronidazole or furizolidone, which are all prescribed by doctors. Some individuals may recover without medication. Preventative measures for giardia are: wash hands thoroughly after toilet visits, carefully dispose of sewage wastes so you do not contaminate surface water or ground water, and always avoid consuming improperly treated water. Giardia cysts are far harder to kill than bacteria or viruses. Giardia cannot be killed by chlorine, iodine, or ultra violet light. The best methods to extractgiardia are: filtration using specially designed filters and high temperature boiling.