Perkinsus olseni and other parasites and abnormal tissue structures in New Zealand Greenshell™ mussels (Perna canaliculus) across different seasons

Abstract The New Zealand Greenshell™ mussel ( Perna canaliculus ) supports the largest aquaculture industry in the country. However, summer mortality events and potential disease outbreaks may threaten the growth of this industry. As an approach to gauging potential threats through the seasons, a detailed histopathological examination was conducted on 256 adult cultured mussels collected from a farm between April 2018 to September 2019, which covered the austral autumn, winter, spring and summer seasons. Histological sections followed by confirmatory in situ hybridization (ISH) resulted in the identification of Perkinsus olseni at an overall prevalence of 56%. Other parasites and pathogens were identified by histology: apicomplexan parasite X (APX) (78%), copepods ( Pseudomyicola spinosus or Lichomolgus uncus ) (1%), Microsporidium rapuae…