Post-weaning multi-systemic wasting syndrome (PMWS) does not affect humans but attacks young pigs, causing emaciation, diarrhoea and breathing problems, and can kill up to 40 per cent of a piggery's weaners in its early stages.

Found worldwide, apart from Australia, the disease inflicts a high death rate on pigs aged six to 12 weeks, and continuing illness for survivors, including infertility, according to Yahoo! Xtra News.

"PMWS is still infecting new farms ... and even some with very stringent biosecurity practices," New Zealand Pork chief executive Sam McIvor told NZPA.

"It emphasises just how hard to manage some of these modern diseases and viruses are," he said.

"We should not take risks," Mr McIvor said after telling parliamentarians that at a conservative estimate, the disease has now cost the nation's economy at least $44 million.

When the disease was first found on Ted and Irene Graham's Orini piggery, 24km east of Huntly in 2003, the industry argued that the outbreak occurred only after an unidentified infectious agent was fed to pigs in uncooked pork.

It said this probably happened when the Ministry of Agriculture and Forestry (MAF) stopped spending money on enforcing pig swill regulations - which required people making pig swill to boil the food - and before new controls were introduced on cooking imported meat.

The disease later "exploded" across farms which kept pigs outdoors: "Spread, we believe, by gulls, sparrows, flies, an errant truck driver and weaner pig movements before it was recognised," Mr McIvor told the primary production select committee probing the Biosecurity Law Reform Bill.

"In the South Island, we now have about 80 percent of the herds with it and the initial mortality was 18 percent of pigs on those farms."

It had cost farmers $15m in lost income - as well as the money spent on breeding piglets which later fell sick - and the wider economy had lost another $29m, equivalent to $1.92 for every dollar spent at the farm gate.

The $44m total was "conservative", he said.

"I haven't put a figure on the depression, marriage break-ups, business failures, two deaths and a severe heart attack that were believed to be related to the issue," he told MPs.

There was now an effective vaccine sold for $3 a pig.

But Mr McIvor told the committee that research had shown that a virus that cause a worse disease, incurable porcine reproductive and respiratory syndrome, could arrive in the meat of imported animals.

Though the virus did not have human health implications, it could be transmitted to the New Zealand pig herd with devastating effects on animal health, and pig farmers had been at odds with MAF since 2006, when the ministry proposed a health import standard for pigmeats. NZ Pork also had some "fundamental concerns" around sections of the biosecurity bill, including a shift of focus away from trying to manage risks offshore and at the border.

You can visit our PMWS page by clicking here.