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Diseases of Aquatic Organisms

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DAO 33:151-156 (1998)  -  doi:10.3354/dao033151

Modes of transmission of Loma salmonae (Microsporidia)

R. W. Shaw1,2,*, M. L. Kent2, M. L. Adamson1

1Department of Zoology, 6270 University Boulevard, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
2Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia V9R 5K6, Canada

Loma salmonae (Putz, Hoffman and Dunbar, 1965) Morrison and Sprague, 1981(Microsporidia) causes prominent gill disease in pen-reared chinook salmon Oncorhynchus tshawytscha in the Pacific Northwest. Transmission of the parasite was examined by exposing Pacific salmon Oncorhynchus spp. to infectious spores by various routes: per os, intraperitoneal, intramuscular, and intravascular injection, by cohabitation with infected fish, and by placement of spores directly on the gill. All exposure methods led to infections except placement of spores on the gill. Putative sporoplasms were visible in epithelial cells of the alimentary canal within 24 h of per os exposure. L. salmonae may initially infect alimentary epithelial cells and then migrate into the lamina propria to access the blood stream. Positive results obtained by intravascular injection suggest that autoinfection from spores of ruptured xenomas in the endothelium may also occur. The cohabitation experiment demonstrates that fish may become infected by spores released from live fish.

Loma salmonae · Microsporidia · Transmission

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