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Diseases of Aquatic Organisms

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DAO 104:83-91 (2013)  -  DOI:

Rediscovery of the Yesso scallop pathogen Perkinsus qugwadi in Canada, and development of PCR tests

Naoki Itoh1,*, Gary R. Meyer2, Amy Tabata2, Geoff Lowe2, Cathryn L. Abbott2, Stewart C. Johnson

1Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori Amamiya-machi, Aoba-ku, Sendai 981-8555, Miyagi, Japan
2Pacific Biological Station, Department of Fisheries and Oceans, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T 6N7, Canada

ABSTRACT: Perkinsus qugwadi, a pathogenic protozoan parasite of Yesso scallops Patinopecten yessoensis, is found only in cultured populations in British Columbia, Canada. This pathogen was first identified in 1988 and caused significant mortalities at some locations during the early 1990s. Prevalence of infection decreased dramatically following 1995, and the disease was last reported in 1997, leading to speculation that the Yesso scallop stocks in Canada had developed resistance to the disease, or that P. qugwadi had disappeared. However, the present study revealed that infection with P. qugwadi and associated mortality is still occurring in scallops from at least one location in British Columbia. One of the PCR tests developed for P. qugwadi detected the parasite in a 105-fold dilution of DNA extracted from a heavily infected sample and detected 52% more positive scallops than histology; however, the assay also cross-reacted with P. honshuensis and P. olseni. The other PCR test was less sensitive and detected 34% more positives, but did not react to any of the other Perkinsus species tested, suggesting that these PCR tests are powerful tools for screening for the presence of P. qugwadi. Phylogenetic analysis of 1796 bp of SSU rRNA gene sequence clearly indicated that P. qugwadi is positioned basally to other Perkinsus species.

KEY WORDS: Bivalves · Parasite disease · Perkinsus · Phylogeny · Diagnosis · Molecular detection

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Cite this article as: Itoh N, Meyer GR, Tabata A, Lowe G, Abbott CL, Johnson SC (2013) Rediscovery of the Yesso scallop pathogen Perkinsus qugwadi in Canada, and development of PCR tests. Dis Aquat Org 104:83-91.

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