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Diseases of Aquatic Organisms

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DAO 132:181-189 (2019)  -  DOI: https://doi.org/10.3354/dao03318

PCR and histology identify new bivalve hosts of Apicomplexan-X (APX), a common parasite of the New Zealand flat oyster Ostrea chilensis

Nguyen Thao Suong1,2,*, Jonathan C. Banks2, Andrew Fidler1, Andrew Jeffs1, Kevin C. Wakeman3,4, Stephen Webb2

1Institute of Marine Science, University of Auckland, Auckland 1142, New Zealand
2Cawthron Institute, Nelson 7010, New Zealand
3Institute for International Collaboration, Hokkaido University, Sapporo 060-0810, Japan
4Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
*Corresponding author:

ABSTRACT: Apicomplexan-X (APX) is a significant pathogen of the flat oyster Ostrea chilensis in New Zealand. The life cycle and host range of this species are poorly known, with only the zoite stage identified. Here, we report the use of molecular approaches and histology to confirm the presence of APX in samples of green-lipped mussels Perna canaliculus, Mediterranean mussels Mytilus galloprovincialis and hairy mussels Modiolus areolatus collected from widely distributed locations in New Zealand. The prevalence of APX infection estimated by PCR was 22.2% (n = 99) and 50% (n = 30) in cultured green-lipped mussels from Nelson and Coromandel, respectively; 0.8% (n = 258), 3.3% (n = 150) and 35.3% (n = 17) in wild Mediterranean mussels from Nelson, Foveaux Strait and Golden Bay, respectively; and 46.7% (n = 30) in wild hairy mussels from Foveaux Strait. Histology detected all cases of PCR that were positive with APX and appeared to be more sensitive. The prevalence of APX estimated by histology in green-lipped mussels from Coromandel was 60% versus 50% by PCR, and 4.3%, 10.7% and 52.9% by histology versus 0.8%, 3.3% and 35.3% by PCR in wild Mediterranean mussels from Nelson, Foveaux Strait and Golden Bay, respectively. The specific identity of the parasite found in mussels was determined by sequencing PCR products for a portion (676 bp) of the 18S rRNA gene; the resulting sequences were 99-100% similar to APX found in flat oysters. Phylogenetic analyses also confirmed that all isolates from green-lipped, Mediterranean and hairy mussels grouped with APX isolates previously identified from flat oysters. This study indicates the wide geographical distribution of APX and highlights the potentially multi-host specific distribution of the parasite in commercially important bivalve shellfish.


KEY WORDS: Bonamia exitiosa · Host range · Modiolus areolatus · Mytilus galloprovincialis · Parasitic disease · Perna canaliculus


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Cite this article as: Suong NT, Banks JC, Fidler A, Jeffs A, Wakeman KC, Webb S (2019) PCR and histology identify new bivalve hosts of Apicomplexan-X (APX), a common parasite of the New Zealand flat oyster Ostrea chilensis. Dis Aquat Org 132:181-189. https://doi.org/10.3354/dao03318

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