The highly virulent strain of PEDv that decimated piglet numbers in the US, and is rife in Asia, will almost certainly appear in Europe, and even the UK, according to US vet Dr Greg Kline. Talking to Pig World at the Irish Pig Health Society’s annual symposium at Mullingar, County Meath, yesterday, he said it was inevitable that the virus, which has already affected herds in Ukraine, would start circulating more widely.
However, addressing farmers, vets and members of the allied industries at the society’s 42nd Symposium and Trade Fair, Dr Kline, who’s an enetric disease specialist with Boehringer Ingleheim, suggested that control strategies – starting with excellent biosecurity – could help limit the spread.
“In the US, the PEDv virus was first announced on May 13, 2013, and in just 11 months it had affected 50% of US herds,” he said. “We thought we were experts at biosecurity, but our experience with this virus tells a different story.
“If you look at the situation in Canada, where there first outbreak appeared six months after the first US case, they had been able to put a plan in place to tackle PEDv and limit its spread. It’s been very succesful at limiting the effect of the virus in the Canadian herd.”
Dr Kline said that while the PEDv virus was reasonable easy to kill with heat and disinfectants, the problem was that it multiplied very quickly and could exists in such large numbers that it was difficult to deal with every cell. Even if you used a disinfectant that could kill 99.999% of the viral load, that would still leave one million PEDv cells, and the infective dose was just 100.
The virus was also very easy to spread on pigs, people and vehicles, and would even spread on dust particles in the wind. He said researchers had proved that spread via the wind was just about inevitable (risk increased by a factor of four) on farms up to two miles apart – and this had been proved by the fact that in pig-dense areas of the US, every unit would break down with the disease in just one week.
The risk of getting infected was doubled if you were situated between three and four miles afrom an infected unit, and only if yu were more than four miles away could spread of the virus on the wind be ignored.
It has quickly been established that all piglets affected before eight-days old would die, and many units would now euthanise all piglets as soon as the disease hit. This was taking a toll on the farm staff, Dr kline said, as stockmen that had spent their lives raising pigs had to deal with 100% mortality in the herds where they worked. This had resulted in many leaving the industry and vowing never to return to pig production.
On US farms, Dr Kline said the effects of the virus would subside significantly after four weeks and be almost negligible after 13 weeks. And in most cases it was possible to eliminate the virus in about six months by making sure the disease was endemic in the herd to remove virus shedding, and using cleaning and disinfection to remove any live virus. The immunity didn’t last long, however, and about 5% of herds would suffer a “re-break”, that could usually be blamed on a another biosecurity beakdown.
There were some signs for optimism, however, as Dr Kline told Pig World that the batch systems used in the UK and Europe would limit the damage significantly. Depending on the timing of the initial outbreak, most farms on a batch system would have time to infect (feedback) the next batch of sows with PEDv so that their piglets would have immunity to the virus. It was likely that only one batch of piglets would be lost, rather then the three or four that US herds on weekly farrowing had experienced.
Dr Kline also said that he wouldn’t necessarily recommend culling infected herds because it was relatively straightforward to control the virus and eventually eradicate it from a herd.
“Unless you have other problems in the herd, iike PRRS for example, where you’re likely to benefit from repopulation, my own opinion would be that there’s little benefit to culling out the herd,” he said.