Not much is known about myxozoan parasites. Myxozoans are commonly found as
parasites in aquatic vertebrates (esp. fish) as well as some invertebrates. The
phylum of Myxozoa contains two classes: Myxosporea (infect fish, amphibians,
reptiles) and Actinosporea (infect mainly oligochaetes and sipunculids). More than
1,000 species have been described so far. Many of the spores contain chitin
(which cannot be digested by humans) and can pass intact through the
gastrointestinal tract. There is at present little evidence that these organisms can
infect people. However, spores have been recovered from stools of patients with
gastrointestinal problems. Of course this is no proof of pathogenicity. Spores of
Henneguya salminicola have been detected in stool samples of human patients.
Since they morphologically resemble spermatozoa, misidentification can occur. The
teardrop-shaped spore measures about 10 µm in diameter and has a tail of about
40 µm. Most spores have two pyriform polar capsules situated in the anterior
region of the spore body. They stain with modified trichrome stain. Iodine
preparations and acid-fast stains can be employed, but at present there is
insufficient information on these organisms.