Med. Weter. 68 (12), 728-731, 2012

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Pękala A., Paździor E.
Marteiliosis of oysters – an invasive disease of molluscs
Marteilia refringens is a protistan belonging to the phylum Paramyxea. This parasite is the causative agent of marteiliosis, a lethal diseases that causes mass mortality among molluscs, especially flat oysters (Ostrea edulis). The susceptible species of molluscs also include blue mussels (Mytilus edulis) and Mediterranean mussels (M. galloprovincialis). Depending of the host species, two types of M. refringens have been distinguished: type O, diagnosed in oyster; and type M., occurring in mussels. A new genetic type C is suspected to occur in molluscs belonging to the Cerastoderma edule species. M. refringens displays tropism to digestive epithelium, and in heavy infections the parasite causes total damage of the digestive gland. The presence of these parasites in a mussel only weakens the host. The life-cycle of M. refringens is complex. The transmission of the parasite presumably also involves other host species, such as in copepodes and zooplankton. The development of the parasite is seasonal and strictly related to water temperatures. The diagnosis of marteiliosis is carried out by tissue imprints, histology and molecular methods. The treatment of marteiliosis is impossible, and therefore the only way to control the disease is to prevent the spread of the pathogen. Marteiliosis of oysters is listed as an O.I.E notifiable disease and classified as a non-exotic disease, according to Council Directive 2006/88/EC.
Key words: Marteilia refringens, flat oysters, mollusc diseases