Microsporidiosis of Dredge Oysters
Category 3 (Host Not in Canada)
Common, generally accepted names of the organism or disease agent
Scientific name or taxonomic affiliation
Unidentified species of Microspora currently placed in the collective group Microsporidium rapuae.
Foveaux Strait, New Zealand
Ostrea chilensis (=Tiostrea chilensis, Ostrea lutaria)
Impact on the host
Induces formation of oval cysts (20-70 µm) in connective tissue surrounding the gut. These cysts, only visible in histology, contain numerous spores surrounded by more or less concentric layers of fibrous elements infiltrated by haemocytes.
Histology: Cysts, as described above, contain numerous oval and refractive spores (5.2 µm x 2.57 µm in frozen sections and 4.7 µm x 2.39 µm in plastic embedded sections). The spore has a polar cap at the apex with an attached polar filament of 19-22 coils and a single nucleus. Sporogenesis and number of spores per pansporoblast are not known.
Methods of control
No known methods of prevention or control.
Jones, J.B. 1981. A new Microsporidium from the oyster Ostrea lurida in New Zealand. Journal of Invertebrate Pathology 38: 67-70.
Sparks, A.K. 1985. Synopsis of Invertebrate Pathology Exclusive of Insects. Elsevier Science Publishing Co., Amsterdam. p. 272.
Bower, S.M. (2006): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Microsporidiosis of Dredge Oysters.
Date last revised: August 2006
Comments to Susan Bower
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