Working Group on Pathology and Diseases of Marine Organisms (WGPDMO)

The work of the ICES WGPDMO is focused on the impact of disease in marine organisms, specifically in relation to infectious diseases. The group meets annually to discuss and summarise the disease trends of the member countries and identify new and emerging diseases of significance. The group is also tasked with maintaining and updating the ICES Disease leaflet Series. Over the duration of this reporting cycle the group will also look to develop a Terms of reference (ToR) focused the impact of climate change on the diseases of marine organisms. The WGPDMO is also building relationships with other relevant working groups to see how other groups might incorporate disease impact into their overviews or advice. This report summarizes the information presented during the 2025 WGPDMO expert group meeting covering trend data for the calendar years 2023 and 2024 (ToRa) and notes progress on ToRs b to d (2025–2027) . However, some historical perspective is included from member countries who have been unable to provide national reports or attend the meeting in recent years. Over the period, a number of increasing trends for endemic diseases which could potentially be related to climate change were identified. Novel pathogens and variants of existing pathogens were identified in fish as well as molluscs and crustaceans. Examples include the description of a putative novel Piscirickettsia species (provisionally named P. nova) in Atlantic salmon in Ireland and Scotland; new variants of Infectious pancreatic necrosis virus (IPNV) in IPNV resistant Atlantic salmon in Norway and Scotland; and the identification of a novel herpes-like virus (OeHV) in European flat oysters in England and Scotland. In 2024, an expansion of the geographical range of the protistan parasites Perkinsus marinus and Haplosporidium nelsoni was reported in Canada and the USA, including the first detection of the notifiable Perkinsus marinus in Canadian waters. An expansion of crab species found hosting the amoeba Janickina feisti was also reported over the period in England. Correction (26 June 2025): A new version has been uploaded with a correction of one of the authors names.