Parasite	Microsporidium sp.
Taxonomy	Microspora, Microsporea
Host	Japanese jack mackerel (Trachurus japonicus)
Infection site	Trunk muscle
Clincal sign	White cysts (a few mm in size) are observed in the trunk muscle.
Parasitology	Many spores are formed inside the cysts (Fig. 1). The spore is rod-shaped (average length 7.5 mm; average width2.0 mm). The formation of sporophorus vesicle has not been confirmed.
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 cysts. Sample should be smeared and stained by Uvitex 2B followed by a fluorescent microscopic observation. The stained spores emit blue fluorescence under UV radiation (Fig. 2).
Other information	Generally speaking, spores of microsporidian are bean-shape. Rod-shaped microsporidian of fish is very unusual.
References	None

Fig. 1. Fresh spores of Microsporidium sp. from the trunk muscle
of Japanese jack mackerel..

Fig. 2. Uvitex 2B-stained spores of Microsporidium.