On the basis of Biosecurity Queensland (BQ) surveillance April 2020 which detected 112 mangrove crabs positive to white spot syndrome virus (WSSV), and their confirmation just a few weeks later that two farms on the Logan River had samples testing positive for WSSV, APFA Management Committee identified a need for a qualified epidemiologist to undertake comprehensive modelling to:
1) Identify what vectors/sentinels are involved in the spread of WSSV and design surveillance for these
2) Investigate at what rate WSSV is spreading by defining the current zone
3) Understand how seasonal factors could impact the spread
4) Advise whether the boundary of the current zone is likely to be changed.
There is significant surveillance data available from several studies and several years of surveillance. This data has not undergone extensive, systematic and comprehensive analysis to determine risk factors, spread etc. There is information suggesting that sentinel vectors carrying WSSV can change year to year and it is important to predict what vectors will be involved in spreading WSSV in the future to ensure appropriate biosecurity measures and monitoring can take place. Clear independent epidemiological advice around the potential sources and likely spread is needed. Working out which animals form proper sentinels is important and will not only describe how WSSV moves around in the environment, what the zones look like, but also how to target mitigation measures.
This information will assist the prawn farming industry initiate appropriate management practices on an enterprise and regional level and to improve their biosecurity plans and potentially inform industry and policy makers on the benefits of a regional or zone-based management plan. Understanding whether WSSV remained within the environment at low prevalence for 2017-2020, or whether there was a separate incursion in 2020 is beneficial because the management protocol will be different in each scenario. In addition, understanding of risk factors will assist predictions about where and if this virus is most likely to spread?
