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Health Status of Olympia Oysters (Ostrea lurida) in British Columbia, Canada

ABSTRACT 
 
 The Olympia oyster (Ostrea lurida) is the only oyster species native to British Columbia, Canada. Despite management regulations designed to protect this species, populations continue to decline in many locations. In an effort to determine whether parasites or disease are contributing to the population decline, oysters were collected from 5 locations and examined for the presence of pathogens and disease using histology and polymerase chain reaction (PCR) assays. Five parasite/symbiotic organisms were detected by histology, including Rickettsia-like prokaryotes, Mytilicola sp., Rhynchodida-like ciliates, encapsulated copepods, and an unknown protist. Six pathologies of unknown etiology were also detected, including hemocytic neoplasia, basophilic inclusions in the digestive gland epithelium, metaplasia of digestive gland tubules, diapedesis, and diffuse and focal hemocyte infiltration. Despite the variety of histological findings, most were detected at low prevalence and intensity, and are not believed to have a significant impact on the health of oysters at the individual or population levels. In addition, 7 different PCR assays were conducted for known bivalve pathogens, including Mikrocytos mackini, Haplosporidium spp., and Bonamia spp. Although all PCR test results proved to be negative, some assays did produce nonspecific amplification products, emphasizing the need for caution and validation when applying PCR assays to new hosts and new geographical regions. Although the current study did not identify any pathogens or diseases of concern, it provides important baseline data for future health assessments.