Parasite Henneguya salminicola
Taxonomy Myxozoa, Myxosporea, Bivalvulida
Hosts Coho salmon (Oncorhynchus kisutch), Chinook salmon (Oncorhynchus tshawytscha), Pink salmon (Oncorhynchus gorbuscha), Sockeye salmon (Oncorhynchus nerka), Chum salmon (Oncorhynchus keta), Rainbow trout (Oncorhynchus mykissj
Infection site Trunk muscle
Clinical signs White cysts (a few mm) are observed in the trunk muscle (Figs. 1, 2). In the frozen

fish or smoked fish, the site of infection looks like 'a milky condition' (Awakura and Kimura, 1977).

Parasitology Cysts are filled with a number of spores (Fig. 3). A spore (average length 10.7 m; average width 8.7 m; average thickness 6.1m) is oval and has 2 slightly unequal polar capsules (larger one: average length 4.2 m; average width 2.5 m, smaller one: 3.8 m; 2.2 m) and 2 caudal appendages (longer one: average length 34.8 m, shorter one: 28.9 m). The life cycle is unknown. The alternate host is probably involved in the life cycle.
Pathology The parasite was encapsulated by the hostfs connective tissues and formed the cysts.
Health hazard Since this parasite is not infectious to human, it is harmless in food hygiene.
Diagnosis Check the spores by the wet-mount of cysts or degenerated muscle tissue. Sample should be smeared and stained by Giemsa.
Other information Some authors suggested that Henneguya salminicola is synonym of Henneguya zschokkei (Lom and Dykova, 1992).
References Awakura T. and T. Kimura (1977): On the milky condition in smoked coho salmon (Oncorhynchus kisutch) caused by myxosporidian parasite. Fish Pathol., 12, 179-184.

Lom, J. and I. Dykova (1992): Protozoan parasites of fishes. Elsevier, New York, 315p.

(Photos by Jun Araki)

Fig. 2. Lesions caused by H. salminicola

Fig. 3. Fresh spores of Henneguya salminicola

Fig. 1. Trunk muscle of pink salmon infected with Henneguya.