Cryptosporidium
A protozoan parasite, has been recognized to be a human pathogen since 1976. The protozoate is transmitted by the ingestion of oocysts that have been excreted in the feces of infected humans or animals. Similarly to Giardia, Cryptosporidium can also be transmitted by the ingestion of fecal contaminated water. Several species of Cryptosporidium are known to exist but only Cryptosporidium parvum is known to be infective to humans. After release into the environment, the organism is protected by an outer shell called an oocyst. Each oocyst contains four sporozoites with one nucleus per sporozoite. Upon ingestion, the organism emerges from the shell and infects the lining of the intestine. The United States Environmental Protection Agency Method 1623 (used for detection of Giardia and Cryptosporidium) defines a sporozoite and nucleus in the following manner:
- Sporozoite - a motile, infective stage of certain protozoans; e.g., Cryptosporidium. There are four sporozoites in each Cryptosporidium oocysts, and they are generally banana-shaped.
- Nucleus - A membrane-bound organelle containing genetic material. Nuclei are a prominent internal structure seen both in Cryptosporidium oocysts and Giardia cysts. In Cryptosporidium oocysts, there is one nucleus per sporozoite. One to four nuclei can be seen in Giardia cysts.
Above:
Immunofluorescence image of several Cryptosporidium parvum oocysts. Oocysts were stained with commercially
available immunofluorescent antibodies. Oocysts should have an intense apple green fluorescence
on the periphery of their oocyst wall, and measure 4 to 6 microns in diameter. Scale bar is 10 microns.
Photo Credit: H.D.A. Lindquist, U.S. EPA
Cryptosporidium oocysts are 3-7µm in diameter and virtually impossible to destroy using conventional methods. However, Cryptosporidium oocysts are removed via filtration in our water treatment process.
For more interesting information regarding Giardia, click on the hyperlink to visit the USEPA (United States Environmental Protection Agency) USEPA Microbiology Homepage.
You can also learn more about Giardia by visiting the American Water Works Association website and read the fact sheet that they have compiled.
Please feel free to send any water quality comments or questions that you may have to waterquality@tmwa.net.
