Work

Interplay between immune cell damage and depletion, population size, ecological factors and Picornavirus infection in the Venice Lagoon (Italy)

Year: 2026

Type: article

Abstract: We monitored the disease condition of the fan mussel Pinna nobilis (L.) in the Venice lagoon (North of Italy) during a period of one and half year (2023–2024) in two areas named Ottagono Alberoni (OA) and Coffa Val Grande (CV). Host and environmental factors (e.g. pen shell age, state of infection, oxygen, temperature, salinity, immune cell depletion with activation of caspase-3) were investigated and shown to influence morbidity and mortality progressiveness in the two areas. During the study period, Pinna nobilis Picornavirus ( PnPV ) caused systemic hemic infections in all examined individuals (100%) compromising the organelle compartment of the cells. Ultrastructure revealed widespread viral replication organelles (vROs) occupying most of the host immune cells that arose from a total rearrangement of cytoskeletal membranes that were dedicated to the virus machinery. Our results demonstrate a positive correlation between relative mortality and size classes, showing a higher mortality percentage across all classes, highlighting local differences. Younger, smaller individuals in CV showed higher tolerance and lower mortality rates due to milder viral infections. Conversely, larger adults in OA suffered a 100% mortality rate, leading to the extinction of that population by October 2024. Total Hemocyte Count (THC) was lower in OA (1.77 ± 0.16 and.2 ± 5 x 10 4 cells/ml) compared to CV (1.65 ± 8 x 10 5 − 2.62 x 10 5 cells/ml) and with a positive correlation with viral load, connected with percentage of dead cells percentage, in turn correlated with animal size, suggesting that number of immune cells is regulated by the level of infection, and also age. Picornaviruses are highly resistant to environmental variables which allow them to persist for long periods in aquatic ecosystems. Viral seasonal presence and interaction with environmental variables need to be clarified.

Source: Scientific Reports

DOI: 10.1038/s41598-026-77671-7