Metal stresses affect the population dynamics of disease transmission in aquaculture species

The purpose of this study is to develop a mechanistic-based population dynamics of disease model to predict the effect of heavy-metal stresses on the susceptibility of the aquaculture species to pollution-associated infectious diseases. We link an ecologically based nonlinear epidemiological dynamics of host-parasite interactions with a deterministic susceptibility-infectious-mortality (SIM) model to evaluate the host susceptibility to the waterborne metal stressors. We test the proposed pollution-associated population dynamics of disease model against published data regarding the effect of metal cations (Cd2+, Cu2+, and Hg2+) on the susceptibility of hard clam (Meretrix lusoria) to birnavirus. We estimate stressor-specific transmission rate and basic reproductive number (R0), defined as the average number of secondary cases generated by one primary infected case, by fitting SIM model to published cumulative mortality data. The median pollution-associated R0 estimates range from 0.99 to 1.03. Here we show that the interplay of environmental chemical stressors and disease transmission explains the host-pathogen interactions presenting in the immunomodulating chemicals contaminated aquacultural systems, suggesting that predicting schemes will require the consideration of both environmental stressor variability and host size in aquaculture species populations. We suggest that in the future potential management actions the pathogen manipulation is better to be integrated to improve the on-line environmental stressors monitoring in aquacultural systems.