Henneguya salminicola

From Fish
Trunk muscle of pink salmon infected with Henneguya
File:Henne02.jpg
Lesions caused by H. salminicola
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Fresh spores of Henneguya salminicola

Henneguya salminicola is a myxosporidian parasite (Taxonomy: Myxozoa, Myxosporea, Bivalvulida) of fish.

It is known to parasitise the trunk muscle of Coho salmon (Oncorhynchus kisutch), Chinook salmon (Oncorhynchus tshawytscha), Pink salmon (Oncorhynchus gorbuscha), Sockeye salmon (Oncorhynchus nerka), Chum salmon (Oncorhynchus keta) and Rainbow trout (Oncorhynchus mykiss

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[1].

Cysts are filled with a number of spores. A spore (average length 10.7 μm; average width 8.7 μm; average thickness 6.1μm) is oval and has 2 slightly unequal polar capsules (larger one: average length 4.2 μm; average width 2.5 μm, smaller one: 3.8 μm; 2.2 μm) and 2 caudal appendages (longer one: average length 34.8 μm, shorter one: 28.9 μm). The life cycle is unknown. The alternate host is probably involved in the life cycle[2].

Since this parasite is not infectious to human, it is harmless in food hygiene.

Diagnosis

Diagnosis is based on finding encysted spores by the wet-mount of cysts from degenerated muscle tissue. Sample should be smeared and stained by Giemsa.

References

  1. 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
  2. Lom, J. and I. Dykova (1992) Protozoan parasites of fishes. Elsevier, New York, P:315