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Diseases of Aquatic Organisms

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DAO 57:227-230 (2003)  -  doi:10.3354/dao057227

Ultrastructural evidence of autoinfection in the gills of Atlantic cod Gadus morhua infected with Loma sp. (phylum Microsporidia)

Luis E. Rodriguez-Tovar1, Dorota W. Wadowska2, Glenda M. Wright3, David B. Groman4,*, David J. Speare4, Darryl S. Whelan5

1Department of Pathology, College of Veterinary Medicine, Autonomous University of Nuevo Leon, CP 64930 Monterrey, Mexico
2Electron Microscopy,
3Department of Biomedical Sciences, and
4Aquatic Diagnostic Services, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3, Canada
5Newfoundland Department of Fisheries and Aquaculture, St. John¹s, Newfoundland A1B 4J6, Canada
*Corresponding author. Email:

ABSTRACT: Infection by a microsporidian of the genus Loma was found in gills of cod Gadus morhua. Xenomas contained parasites in multiple stages of development. Some spores looked empty and had everted polar tubes, which were either straight or coiled. These polar tubes were scattered throughout the xenoma cytoplasm, and some of them pierced the plasma membrane. Those outside of the xenoma penetrated neighboring cells, including blood cells. These observations suggest that a mechanism of autoinfection could occur in blood cells and gill tissue, perpetuating the disease in the host.

KEY WORDS: Ultrastructure · Microsporidia · Xenoma · Everted polar tube · Autoinfection · Loma sp. · Cod

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