Haplosporidium (=Minchinia) armoricana of Flat Oysters


Category 1 (Not Reported in Canada)

Common, generally accepted names of the organism or disease agent

Minchinia armoricana, European oyster minchiniasis, Haplosporidian disease of flat oysters.

Scientific name or taxonomic affiliation

Haplosporidium (=Minchinia) armoricana as revised by Azevado et al. 1999.

Geographic distribution

Brittany and Arcachon, France, Spain and the Netherlands. Haplosporidian plasmodia have also been reported in Olympia oysters from Oregon, USA that were imported from California (Mix and Sprague 1974).

Host species

Ostrea edulis and Ostrea angasi. Possibly also in Olympia oysters, Ostrea conchaphila (=lurida).

Impact on the host

Infected oysters are thin and watery in appearance and have a characteristic brownish colour caused by masses of spores in the connective tissues. Although the disease is fatal, the prevalence of infection to date has been low (less than 1%) with insignificant impact on the flat oyster culture industry in Europe. However, an acclimatization experiment with O. angasi in France indicated that this introduced species of oyster was exceptionally sensitive to infection (Bougrier et al. 1986).

Diagnostic techniques

Wet Mounts: At opposite ends of the spore are two characteristic long (70-100 µm) projections of the outer spore wall (especially evident in interference light microscopy).

Histology: The connective tissue of infected flat oysters contains plasmodia (17-25 µm in diameter), sporonts (30-45 µm), and sporocysts (35-50 µm) containing 100-150 spores (5.0-5.5 x 4.0-4.5 µm).

Electron microscopy: The spores are ellipsoid (about 5.0 µm long and 3.1 µm wide) with an operculum and ornamented with two long episomal cytoplasm extensions (about 130 µm long and 25 nm thick) attached eccentrically at opposite sides of the spore wall by a bundle of 9 to 13 cylindrical fibers. The nature of the spore ornamentation indicated that this parasite belongs in the genus Haplosporidium and not Minchinia (Azevado et al. 1999).

Methods of control

No known methods of prevention or control.


Azevedo, C., J. Montes and L. Corral. 1999. A revised description of Haplosporidium armoricanum, parasite of Ostrea edulis L. from Galicia, northwestern Spain, with special reference to the spore-wall filaments. Parasitology Research 85: 977-983.

Bachère, E., D. Chagot, G. Tigé and H. Grizel. 1987. Study of a haplosporidian (Acetospora), parasitizing the Australian flat oyster Ostrea angasi. Aquaculture 67: 266-268.

Bonami, J.R., C.P. Vivares and M. Brehelin. 1985. Étude d'une nouvelle haplosporidie parasite de l'huître plate Ostrea edulis L.: morphologie et cytologie de différents stades. Protistologica 21: 161-173. (In French, with English summary).

Bougrier, S., G. Tigé, E. Bachère and H. Grizel. 1986. Ostrea angasi acclimatization to French coasts. Aquaculture 58: 151-154.

Mix, M.C. and V. Sprague. 1974. Occurrence of a haplosporidian in native oysters (Ostrea lurida) from Yaquina Bay and Alsea Bay, Oregon. Journal of Invertebrate Pathology 23: 252-254.

Perkins, F.O. and P. van Banning. 1981. Surface ultrastructure of spores in three genera of Balanosporida, particularly in Minchinia armoricana van Banning, 1977 - the taxonomic significance of spore wall ornamentation in the Balanosporida. The Journal of Parasitology 67: 866-874.

Pichot, Y. 1986. Sporulation d'Haplosporidium sp. (Haplosporida, Haplosporidiidae) chez l'huître Ostrea edulis L. du bassin d'Arcachon (France). European Aquaculture Society, Special Publication 9: 119-126. (In French, with English abstract).

Sparks, A.K. 1985. Synopsis of Invertebrate Pathology Exclusive of Insects. Elsevier Science Publishing Co., Amsterdam. p. 285-286.

van Banning, P. 1979. Haplosporidian diseases of imported oysters, Ostrea edulis, in Dutch estuaries. Marine Fisheries Review 41: 8-18.

van Banning, P. 1985. Minchinia armoricana disease of the flat oyster. In: C.J. Sindermann (ed.) Fiches d'Identification des Maladies et Parasites des Poissons, Crustacés et Mollusques. No. 17. ICES, Copenhague 4 pp.

Citation Information

Bower, S.M. (2006): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Haplosporidium (=Minchinia) armoricana of Flat Oysters.

Date last revised: December 2006
Comments to Susan Bower

Date modified: