A devastating disease is threatening pig production in the United States.

Since May last year, the Porcine Epidemic Diarrhoea virus (PEDv) has decimated pig herds across the United States' 'hog belt'. First discovered in Ohio, the disease has passed into new areas of the north and east, with almost 6,000 cases now having been reported.

Though older pigs generally survive infection, the virus attacks the gut of piglets, preventing them from absorbing fluids and causing them to die of dehydration. The National Pig Association (NPA) in the UK has expressed alarm over the devastating progress the disease could make before the national herd starts to develop antibodies.

So far, seven million animals have succumbed to the disease in 30 US states, and cases have been detected over the border in Canada and Mexico. There is no known cure and US authorities do not know how the disease came about; although researchers have established that PEDv is similar to a virus that affected pigs in Anhui province, China in 2011, and viruses of the same family have affected pigs in Japan, Europe and South America, albeit in much milder forms.

USDA makes PEDv notifiable

Meanwhile in the US, PEDv was only classified as a notifiable disease in late April and, as yet, there have been no international restrictions placed on exports from the country. USDA has come under fire from pig industry groups for failing to make PEDv notifiable in 2013, when it became clear that the virus was spreading, and EU Commission sources have this week revealed that there are no harmonised measures in place to deal with PEDv.

Although PEDv is said by experts to be a 'cold weather virus', spreading most easily during the winter, the disease's rapid sweep through North America means that even if its progress is slowed by the onset of warmer weather, the pig industry will still be reeling from its recent effects; yesterday the US National Pork Producers Council forecast that pig prices could increase dramatically as a result of PEDv. The council forecast rises of up to 25 percent, with increases of between 10 and 12 percent being passed on to consumers.

Though the disease is likely to have huge impacts on production, NPPC President Howard Hill told members of a Congressional Committee on Wednesday that consumer demand for pig meat has so far remained unchanged in the US – even in the face of higher prices. He said this could mean producers who have not been affected will reap higher profits and even those who have lost animals may be surprised at their returns. However, the sobering truth is that US producers have much to fear from the new disease, as much about PEDv remains unknown and in the space of a single year the virus has killed an estimated 10 percent of the country's pig herd.   

Europe unprepared.

"We are just watching with horror how it is rampaging across America, and no-one in Europe seems to be the least bit interested," Zoe Davies, general manager of Britain's National Pig Association, told Reuters. It could reach Europe in the coming months, and little has been done to try to prevent its arrival, industry sources said.

Specialist pig vets in the UK have warned that if PEDv arrived in Britain it would spread quickly through the nation's pig population, causing "incalculable damage." In March, BPEX vet Derek Armstrong said, "It is impossible to overstate the damage PEDv would cause if it arrived in Britain. The evidence from the States is that it is so outstandingly infectious that just one infected pig is all it would take to start an epidemic in this country which could kill as much as ten percent of the national herd."

NPA chairman Richard Longthorp said, "We are clear that we don't want to be looking back in a few months, and wish we had been more cautious. We are all agreed in the pig sector that we should close off every avenue of risk and potential risk for the time being."

Further details on PEDv

On 29 April 2013, the Iowa State University Veterinary Diagnostic Laboratory received the first four of what quickly became many submissions from swine farms experiencing explosive epidemics of diarrhoea and vomiting, resulting in 90-95 percent mortality in suckling pigs. Within nine weeks of the first outbreak, cases of the virus had been identified in 16 states. According to experts at the National Veterinary Services Laboratories, the almost simultaneous outbreaks of disease, and high degree of similarity between the strains sent for testing, suggest that the virus emanates from a single common source.

Epidemiologists suggest that the disease is transmitted by faecal matter – worryingly, the virus appears to be so infectious that experts have stated one tablespoon of infected faeces could infect the entire US swine herd. Recent studies have also suggested that sow milk could represent another possible (and potentially major) route for the vertical transmission of PEDV from sow to suckling piglet.

Veterinarians have expressed concern about the potential role highly centralised facilities and equipment where pigs are transported, slaughtered and processed in the US could be playing in the spread of the disease. Experts at the Department of Veterinary Clinical Medicine, University of Illinois warned that evidence suggests "The transport process is a source of transmission if adequate hygiene measures are not implemented."

They suggested that, as is often the case, "control measures may be implemented too late to limit the spread of the disease through [vectors such as] contaminated vehicles returning from swine collection points." Experts have nevertheless urged industry and regulators to adopt a coordinated range of "simple biosecurity measures" that could reduce the risk of spread.  

Many big farms and hauliers in the US are belatedly adopting strict biosecurity measures and putting up signs in badly affected regions to warn others where and when the disease has struck.

The American Association of Swine Veterinarians (AASV) has been publishing weekly updates on the virus' progress. AASV testing revealed that feed and feed ingredients have had no part to play in the introduction or transmission of PEDv.

PEDv does not appear to be harmful to humans.

Sources

http://wwwnc.cdc.gov/eid/article/20/5/13-1628_article.htm May 2014
http://www.ncbi.nlm.nih.gov/pubmed?cmd=Retrieve&list_uids=23963154&dopt=Abstract 2013 Aug 20.