Modelling Carpageddon [MCB]
The Australian government is considering the deliberate release of Cyprinid herpes virus 3 (CyHV-3) to control invasive common carp (Cyprinus carpio) in the Murray-Darling Basin of south-east Australia. The virus emerged in the late 1990s and has since caused serious economic losses in aquaculture and successfully spread to wild carp populations across the northern hemisphere. The release of CyHV-3 is highly controversial with some critics concerned that decomposition following mass-mortality of carp will lead to severe oxygen depletion from the water column and subsequent anoxic events, while other critics argue that a bigger problem is low efficacy. In this talk I will describe the epidemiological modelling commissioned by the federally funded National Carp Control Plan (NCCP) to predict the dynamics of CyHV-3 following a possible virus release. While the epidemiological model itself is simple it is integrated with a sophisticated metapopulation model for common carp in which expert opinion and environmental datasets have been combined via Bayesian Belief Networks (BBN) to determine spatio-temporal habitat suitability for survival and recruitment. The impact of the virus depends most clearly on the presence of a latent disease state that allows for virus reactivation to occur in individual carp in spring and onward infection to new generations of carp. The model dispels the notion that Carpageddon is inevitable and predicts that long-term suppression of the carp population can occur without noticeable epidemics occurring every season. Broadly then, the modelling supports release of the virus while focusing attention on key assumptions that need to be confirmed with further experiments prior to virus release.
Associate Professor Stephen Davis, RMIT