White spot syndrome virus (WSSV) was detected in diseased farmed prawns by Biosecurity Queensland’s Biological Sciences Laboratory and confirmed by the CSIRO Australian Centre for Diagnostic Preparedness (ACDP) Fish Diseases Laboratory in November/December 2016. This exotic aquatic disease incursion resulted in the infection of all prawn farms, under production, along the Logan River, Queensland. Subsequent WSSV detections in prawns and crabs in northern Moreton Bay resulted in the issuing of a Movement Control Order and subsequent WSSV biosecurity control order under the Biosecurity Act 2014, which prohibited the movement of potential carriers (e.g. polychaete worms and decapod crustaceans) from Moreton Bay. These restrictions included wild caught prawns from Moreton Bay which were distributed nationally as bait for recreational fishing. Industry established protocols to treat these prawns, for distribution as bait, using gamma irradiation to a dose of 50 kilogray (kGy). However, this treatment understandably resulted in increased costs of the final product, raising concerns that this would make imported commodity prawns a more likely source of bait for recreational fishing and consequently a biosecurity risk for introduction of exotic diseases.
The primary objective of this project was to determine whether gamma irradiation treatment of WSSV infected prawns at a dose lower than 50 kGy would inactivate the virus as the bait wholesale industry indicated that a reduction in treatment dose to 25 kGy or lower would be required to provide meaningful cost benefits. Given the absence of information on irradiation doses for inactivation of WSSV, this collaborative project involving Department of Agriculture and Fisheries, Queensland, CSIRO ACDP, Steritech and industry, conducted research to evaluate the effect of reduced doses of gamma irradiation (10 kGy, 15 kGy, 20 kGy and 25 kGy) on inactivation of WSSV in infected prawns.
