Government and trade officials are down-playing any likelihood of trade impacts after confirmation that a prion illness, atypical scrapie, occurs in New Zealand sheep.
It is the first confirmed case of a prion disease in New Zealand farm animals since 119 sheep flocks were culled 50 years ago to eradicatean incursion of classical scrapie.
Though New Zealand is free of the brain-wasting disease in sheep and goats, the different condition of atypical scrapie has been found in the brain of a New Zealand sheep tested in Belgium.
The find was made last July in a Romney sheep brain sent in a 2008 shipment for use in European laboratories, despite material from that brain having previously tested negative for atypical scrapie.
The subsequent positive test was confirmed last week.
Ministry of Agriculture and Forestry principal international adviser on animal health Stuart MacDiarmid said it appeared that the infection was not evenly distributed through the brain.
"A number of the tests were just on bits of the brain where there was not an accumulation of abnormal [protein] PrP," Dr MacDiarmid said.
He sought to differentiate the "condition" of atypical scrapie from the classical scrapie disease, which tends to occur in younger sheep and has animal health implications.
Neither illness is known to affect humans, but both are transmissible spongiform encephalopathy (TSE) illnesses, a family of diseases that includes scrapie in sheep and goats, bovine spongiform encephalopathy (BSE), or mad cow disease, in cattle, chronic wasting disease in deer, and Creutzfeldt-Jakob disease (CJD) in people.
Dr MacDiarmid said the condition apparently arose spontaneously, particularly in older sheep.
The deputy director of export standards for the Food Safety Authority, Bill Jolly, said the discovery was a "scientific curiosity" of no real trade relevance.
