Coculture with Eastern oysters is unlikely to reduce OsHV-1 impacts to farmed Pacific oysters: A modelling approach

In recent decades, the global expansion of Pacific oyster Magallana gigas aquaculture, driven by this species’ adaptability and rapid growth, has coincided with the emergence of novel and virulent microvariants ( mu vars) of Ostreid herpesvirus 1 (OsHV-1), causing significant industry losses. As a potential alternative, the eastern oyster ( Crassostrea virginica ) demonstrates lower susceptibility to OsHV-1. This study developed a transmission model for OsHV-1 in mixed oyster aquaculture systems, focusing on the impact of C. virginica introductions on transmission dynamics within established M. gigas systems. The model considers oyster growth, mortality, filtration, viral particle release, and environmental decay. In the absence of experimental data on OsHV-1 infection dynamics in co-culture systems, the model was evaluated using data from monoculture systems. Additionally, the co-culture model was validated for mathematical accuracy and behavior across varying species proportions of M. gigas/C. virginica (90/10, 60/40, 50/50, 40/60, 10/90). Simulation results indicated that introducing C. virginica did not impede OsHV-1 progression; even in the M. gigas/C. virginica 10/90 system, M. gigas mortality reached its maximum, albeit delayed by approximately 10 days. Coculture scenarios did not provide a significant advantage for M. gigas , likely due to OsHV-1 particle saturation in the water column. The model’s performance across diverse scenarios positions it as a valuable tool for understanding waterborne pathogen dynamics in mixed host-species systems, supporting investigations into aquaculture species introductions and their influence on disease dynamics. • A continuous OsHV-1 time model for C. virginica and M. gigas coculture system is developed. • The model is preliminary verified and evaluated against empirical data. • C. virginica introduction into M. gigas system does not limit OsHV-1 infection nor mortality in M. gigas.