Hey Ivan! Long time .....
I know that they exhaustively tested the feed and it was cleared of blame.
The blame really lies at the feet of the importers who brought in the raw infected prawns in the first place, and I gather there have been charges laid against them for avoiding/fraudlent testing of the inbound shipments. They knew exactly what they were doing and didnt care.
IMO those bastards should have been made to wear the full costs of the whole debacle. But international politics and related interests get in the way, of course.
They say we may never definitively, to a criminal standard of proof, be able to prove how the infected prawns got into the waterways. But the most likely source is rec fishers using shop bought, raw, infected imported prawns as bait.