Parasitology

Research Article

Observations raise the question if the Pacific oyster, Crassostrea gigas, can act as either a carrier or a reservoir for Bonamia ostreae or Bonamia exitiosa

S. A. LYNCHa1a2 c1, E. ABOLLOa3, A. RAMILOa3, A. CAOa3, S. C. CULLOTYa1a2 and A. VILLALBAa3

a1 Department of Zoology, Ecology and Plant Science, University College Cork, The Cooperage, Distillery Fields, North Mall, Cork, Ireland

a2 Aquaculture & Fisheries Development Centre, University College Cork, The Cooperage, Distillery Fields, North Mall, Cork, Ireland

a3 Centro de Investigacións Mariñas, Consellería do Mar, Xunta de Galicia, Aptdo.13, Vilanova de Arousa, 36620, Spain

SUMMARY

This study investigated the ability of the Pacific oyster, Crassostrea gigas, to act as a carrier or reservoir of the protistan Bonamia ostreae. Studies were carried out independently in Ireland and in Spain. Naïve C. gigas were exposed to B. ostreae both in the field and in the laboratory via natural exposure or experimental injection. Naïve flat oysters, Ostrea edulis, were placed in tanks with previously exposed C. gigas. Oysters were screened for B. ostreae by examination of ventricular heart smears and by polymerase chain reaction (PCR) screening of tissue samples (gill and/or heart) and shell cavity fluid. PCR-positive oysters were further screened using histology and in situ hybridization (ISH). B. ostreae DNA was detected in the tissues and/or shell cavity fluid of a small number of C. gigas in the field and in the laboratory. B. ostreae-like cells were visualized in the haemocytes of 1 C. gigas and B. ostreae-like cells were observed extracellularly in the connective tissues of 1 other C. gigas. When C. gigas naturally exposed to B. ostreae were held with naïve O. edulis, B. ostreae DNA was detected in O. edulis; however, B. ostreae cells were not visualized. In Spain, B. exitiosa DNA was also detected in Pacific oyster tissues. The results of this study have important implications for C. gigas transfers from B. ostreae-endemic areas to uninfected areas and highlight B. ostreae and B. exitiosa's ability to survive extracellularly and in other non-typical hosts.

(Received September 29 2009)

(Revised November 11 2009)

(Revised January 21 2010)

(Accepted February 03 2010)

(Online publication April 14 2010)

Correspondence:

c1 Department of Zoology, Ecology and Plant Science and Aquaculture & Fisheries Development Centre, University College Cork, The Cooperage, Distillery Fields, North Mall, Cork, Ireland. Tel: +353 (0) 21 4904618. Fax: +353 (0) 21 4904664. E-mail: s.lynch@ucc.ie

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