The surveillance and control programme for bonamiosis and marteiliosis in European flat oysters, Ostrea edulis, and blue mussels, Mytilus sp. in Norway in 2022

Abstract

The surveillance programme is carried out by the Institute of Marine Research according to a contract with the Norwegian Food Safety Authority. In 2022, samples were collected from an area in Agder where flat oysters and mussels are harvested from wild beds and farmed, and from one mussel farm in Trøndelag county. Samples were collected in April/May and in October, to be able to detect Bonamia sp. and Marteilia sp. during the periods when the potential prevalence in affected populatioons is highest. No abnormal mortalities were observed during the surveillance. Bonamia ostreae / B. exitiosa and Marteilia refringens were not detected. Marteilia pararefringens has been observed in Norwegian mussels since 2016 and a targeted surveillance was carried out in 2022. M. pararefringens has so far been detected at eight sites. All Marteilia isolates have been sequenced and typed as Marteilia pararefringens, which is presumed specific for mussels. The work will be continued in 2023, linked to research on the distribution of M. pararefringens in wild mussels. We propose a revision of the surveillance programme and application for disease free status for Bonamia exitiosa in Norwegian flat oysters. We also propose an application for lifting the suspension of free status for Bonamia ostreae in Arendal and Marteilia refringens at Bømlo.

The surveillance and control programme for bonamiosis and marteiliosis in European flat oysters, Ostrea edulis, and blue mussels, Mytilus sp. in Norway in 2022