Graham Clark Graham_Clark at d4.niaid.pc.niaid.nih.gov
Wed Nov 29 16:41:01 EST 1995

In <49frt2$nsq at newsbf02.news.aol.com> stevefunk at aol.com (SteveFunk)

>Is anyone familiar with a protozoan cyst known as microsporidium?  
>Is this a phantom or does it really exist?

Microsporidia are a group of obligate intracellular protozoan parasites 
that are transmitted via a resting stage known as a spore (not a cyst).
They are a very early branch on the eukaryotic phylogenetic tree
and appear to have unusual and small genomes. Beyond morphology
not a lot is known about them, but this is changing because several
species have been found to cause disease in immunocompromised
individuals - the most important being Enterocytozoon bieneusi
which can cause severe diarrhea in AIDS patients. 

Because of the similarity in the names they are often confused with
Cryptosporidium - another parasitic protozoan but totally unrelated.
Over 900 speciesof microsporidia  have been described and are 
parasites of every group of animals so they most certainly are not 

C. Graham Clark, Ph.D.
Laboratory of Parasitic Diseases,
National Institutes of Health,
Bethesda, MD 20892

Ph.: 301-496-4740
FAX: 301-402-4941
e-mail: gclark at nih.gov

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