Detection, isolation, and experimental transmission of Mikrocytos mackini, a microcell parasite of Pacific oysters Crassostrea gigas (Thunberg).
Denman Island disease, characterized by clinical signs of focal green lesions on the body surface or within the mantle, palps, and adductor muscle of Pacific oysters (Crassostrea gigas), is caused by a protozoan parasite of unknown taxonomic affiliations, Mikrocytos mackini. Detection of M. mackini was more sensitive and rapid by use of tissue imprints than histological sections. Of several isolation procedures investigated, centrifugation of homogenized infected tissues through a 15% sucrose solution enabled the isolation of the highest number of M. mackini with the lowest amount of oyster debris. Experimental transmission showed that oysters exposed to M. mackini by inoculation with isolated parasites had shorter prepatent periods and higher prevalences and intensities of infection than those incubated in homogenates from infected oysters (bath exposure) or those naturally exposed in the field. Experimental transmission was also used to propagate M. mackini in vivo in the laboratory year round. For the development of the disease, exposed oysters required prolonged incubation at low temperatures (about 10 degrees C).
Hervio
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Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia, Canada.
Bower
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Meyer
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D000818:Animals; D001955:British Columbia; D056890:Eukaryota / Q000302:isolation & purification*; D010125:Ostreidae / Q000469:parasitology*; D010140:Pacific Ocean; D011528:Protozoan Infections / Q000175:diagnosis / Q000469:parasitology* / Q000635:transmission