Giardia and Cryptosporidium

 

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Here are some fingertip facts about Giardia and Cryptosporidium from the U.S. Food and Drug Administration (FDA) Center for Food Safety and Applied Nutrition's World Wide Web site.

Cryptosporidiosis

Cryptosporidiosis is the illness caused by Crytosproidium, a single-celled protozoa, an obligate intracellular parasite. To date, there is no known effective drug for the treatment of cryptosporidiosis. The infective stage of the organism, or oocyst, is 3 microns in diameter ( about half the size of a red blood cell). Oocysts are resistant to most chemical disinfectants and ultraviolet (UV) light, may be removed with filters that capture all particles of one micron or larger. In some cases the infectious dose can be less than 10 organisms and, presumably, one organism can initiate an infection. The mechanism of the disease is not known. However, the intra cellular stages of the parasite can cause severe tissue alteration.

Giardiasis

Giardiasis is the disease caused by Giardia lamblia, a single-celled animal that moves with the aid of five flagella. Human giardiasis may involve diarrhea within a week of ingestion of the cyst, which is the environmental survival form and infective stage of the organism. In contrast to most bacterial illnesses where hundreds to thousands of organisms must be consumed to produce illness, ingestion of one or more cysts may cause the disease. Cool moist conditions favor the survival of the organism. Giardiasis is more prevalent in children than in adults, possibly because many individuals seem to have a lasting immunity after infection. This organism is implicated in 25 percent of all cases of gastrointestinal disease and may be present in other cases asymptomatically.