Parasite	Microsporidium sp.
Taxonomy	Microspora, Microsporea
Host	Alaska pollack (Theragra calcogramma)
Infection site	Trunk muscle
Clinical sign	An elongated white cyst (a few mm) is observed in the trunk muscle (Fig. 1).
Parasitology	A number of spores are formed in the cyst (Fig. 2). A spore (length ca. 4.0 (3.5-4.0) mm; width ca. 2.0 (1.8-2.3) mm) is ellipsoidal. Two types of the parasite, with and without sporophorous vesicle, were observed, but further examinations are required.
Pathology	No report.
Health hazard	Since this parasite is not infectious to human, it is harmless in food hygiene.
Diagnosis	Check the spores by wet-mount of the foci. The sample should be smeared and stained by Uvitex 2B followed by a fluorescent microscopic observation. The stained spores emit blue fluorescence under UV radiation.
Other information	This parasite was found from Alaska pollack in the surimi plant. Gel forming ability of surimi may be influenced by proteolytic enzymes derived from the parasite.

(Photos by Mark Freeman)

Fig. 2. Fresh spores of Microsporidium from Alaska pollack.

Fig. 1. An elongate cyst (7 mm in length) of Microsporidium in the muscle of Alaska pollack.