PED Update in US and Canada: What a Difference a Year Makes05 June 2015
While new outbreaks of Porcine Epidemic Diarrhoea (PED) continue to be reported each week in the United States, the pace is slowing – as a result of the change in season and the winter of 2014-15 produced fewer outbreaks than the previous year.
It was in April 2013, that the first cases of PED were reported in the US and for about a year, the virus (PEDv) spread across the country to affect 30 of the 52 states.
In early 2014, an additional related virus, porcine delta coronavirus (PDCoV), appeared in this country. These novel Swine Enteric Coronavirus Diseases (SECD) can cause significant morbidity and mortality, particularly in young piglets.
Because the two SECDs were having such a significant impact on the US pork industry, the US Department of Agriculture issued a Federal Order on 5 June 2014, which included two requirements, which effectively resulted in mandatory reporting, namely that:
- Producers, veterinarians, and diagnostic laboratories are required to report all cases of novel SECD to USDA or State animal health officials.
- Herds/premises confirmed to be affected with these viruses must work with a veterinarian – either their herd veterinarian, or USDA or State animal health officials – to develop and implement a reasonable herd/premises management plan to address the detected virus and prevent its spread.
The source of the virus in the US has not been identified but genetic sequencing shows it has more than 99 per cent similarity to one circulating in China in 2011-2012.
It has not just been the US industry that was affected by PED; the virus was also identified in outbreaks in Canada, Mexico, Colombia, Peru and Japan.
Update on Swine Enteric Coronavirus Disease in the United States
SECD includes PED as well as the similar virus porcine deltacorona virus (PDCoV) and the dual infection with both of these viruses.
Since the Federal Order was introduced in June 2014 and reporting became mandatory, a total of 1,314 swine premises have returned results positive for PED, 65 for PDCoV and 50 for the dual infection, according to the USDA Animal and Plant Health Inspection Service (APHIS).
Presumed positive premises total 430, 29 and 28, for the three diseases, respectively, and the numbers of confirmed positive premised that have achieved negative status, i.e. have changed from positive to negative status are 72, five and one, respectively.
As of mid-May, 1,230 premises are positive for the PED virus. The corresponding figures for PDCoV and the dual infection are 59 and 48.
The number of samples tested in official laboratories is approaching 35,000 in the last year alone.
In terms of the geographical location of the affected premises, PED has been reported in a total of 33 states – most recently in Maryland – covering all but the most northwesterly, northeasterly and southeasterly states.
With 33 and 19 affected states, respectively, PDCoV and the dual infection are less widely spread but they too cover the main areas of pig production in the US.
Because these viruses survive well under cold temperatures (when cleaning and disinfection are anyway more challenging) and are not heat-tolerant, there is a seasonal pattern to SECD outbreaks, as they tend to increase during the autumn/fall, peak in mid-winter and decline as the warmer spring weather arrives.
It appears that, despite the introduction of mandatory reporting, there were fewer outbreaks of these enteric diseases in US pigs in the winter of 2014-2015 than the year before.
The US pig association, the National Pork Producers Council (NPPC), believes the sector is gaining control over the infections.
NPPC President, Ron Prestage, DVM, attributed this success to improved farm biosecurity and cleaning – of buildings and transportation – and the likelihood that after initial exposure to the virus, immunity has built up in the sow herd.
He stresses that the arrival of PED in 2013 acted as a wake-up call to the industry. It showed the urgent need for better preparedness to tackle new diseases, he said, and added that the sector is now be in a better position to address future challenges.
The executive director of the American Association of Swine Veterinarians (AASV), Dr Tom Burkgren, confirmed recently to Farmscape that losses in the US from PED have fallen dramatically from one year ago.
He said that, while there is still some circulation of the virus, not as many US sow farms are going down with PED and in those have been affected, mortality has been lower than a year ago.
He has warned, however, that while producers and veterinarians have demonstrated success in ridding individual swine operations of PED, eradication of the virus on a national scale is still a long way off.
Gaining Better Understanding of the PED Virus
Much research has been and continues to be conducted into the SECD viruses in the US.
Among the key breakthroughs identified by the AASV over the last year is work by Dr Scott Dee, who showed that it is possible for a viable PED virus to be transmitted in feed. Previous work had been inconclusive on this issue.
Another study into how the disease can be transmitted showed that airborne transmission should be considered as a potential route for dissemination. Infectious PED virus in the air from experimentally infected pigs and virus genetic material were detected up to 10 miles downwind from naturally infected farms.
In June 2014, USDA APHIS issued a conditional license to Harrisvaccines, Inc. of Ames, Iowa, for a vaccine that may aid in the control of the PED virus – the first to be licensed for this purpose.
Shortly afterwards, Zoetis Inc. was granted a conditional licence for its PED vaccine.
The antimicrobial feed additive, Sal CURB, was found in another study to be effective at controlling the PED virus in feed under trial conditions.
In December 2014, a third strain of the PED virus was identified in the US – strain S2aa-del – in addition to the already known original virus and the one with changes in the spike gene (INDEL). The new strain appeared to cause even more severe symptoms than the original virus.
More recently, a disinfectant based on hydrogen peroxide has been tested against PED virus at Michigan State University, and confirmed to be effective under simulated commercial conditions.
Successful PED Reduction Programme in Canada
On 22 January 2014, the first cases of PED were found in Canada - in the province of Ontario. In the following months, PED outbreaks were seen on farms in Manitoba and Prince Edward Island and the virus was isolated in a slaughterhouse in Quebec.
The most recent farm to test positive for the PEDv in Ontario was in mid-April 2015. It was the 16th outbreak of the 2014-2015 winter, which compares with 63 outbreaks between January and October 2014.
A veterinary epidemiologist with Alberta Agriculture and Rural Development has reported that western Canada's pork industry has continued to keep PED at bay.
Dr Julia Keenliside said recently that there have been no new cases of PED and there have been no environmental positives reported in western Canada over the past month.
With the onset of spring, it becomes much easier to maintain on-farm biosecurity, she added.
A May 2015 update from Ontario Pork highlights how the country’s provincial pig organisations have been working closely with the provincial and federal government and other industry groups on a C$2-million response programme that included a PED Growing Forward programme.
A total of 79 primary PED cases have been identified since January 2014 and of those, more than 55 per cent have successfully eliminated PED from their site. The remaining positive farms are working closely with their veterinarian, and nearly all of these farms have plans in place to eliminate PED virus from their farms this year.
The Ontario Swine Health Advisory Board’s (OSHAB) has enrolled more than 110 sites into the PED Area Regional Control and Eradication (ARC&E) programme. To date, 85 per cent of the enrolled sites have eliminated PED and the final 15 per cent have plans in place to eliminate the disease. Ontario Pork and OSHAB are working together to ensure the sustainability of this programme.
On transportation, OSHAB and Ontario Pork developed and led the Transport Risk Reduction Strategy (TRRS), which identified truck washing as a vital link in biosecurity to control the spread of the virus.
At the beginning of 2014, a dedicated truck wash for high-risk trailers was established in Lucan, Ontario. Transporters could visit the facility and receive a wash and disinfection at this neutral site to prevent or minimise their risk of transferring PED to new locations.
The project was dissolved in February 2015 as truck traffic to the site diminished throughout the year.
Manure applicators were also thought to pose a biosecurity risk.
Following an industry meeting for manure applicators in April 2014, Ontario Pork and the provincial agriculture ministry, OMAFRA, delivered presentations and facilitated discussions of biosecurity measures that can be taken by manure applicators to reduce their risk of transferring PED virus from site to site.
Biosecurity audits of federal and six provincial processing plants were conducted between April and June 2014, which revealed some biosecurity gaps, which have since been resolved.
A federal processing surveillance programme began in May 2014. To date, more than 3,800 samples have been taken and less than two per cent of the samples have come back positive for PED virus.
Communication on PED was an important part of the programme, with seven ‘town hall’ meetings conducted between September 2013 and December 2014, attended by more than 5,700 participants.
More than 20 PED notifications have been emailed to 1,200 producers, vets, transporters, processors and government representatives and PED resources were mailed on three occasions to 2,500 producers, transporters and processors.
Over 100 interviews conducted with major news outlets (radio, TV, print and online) reached an estimated five million individuals and a PED consumer information sheet was emailed to 300 retailers and distributed to 40 health professionals.
There were also a number of presentations at meetings of producers and those who work with transporters, assembly yards, and nutrient applicators.
And finally, a web site dedicated to PED received almost 40,000 views between January 2014 and March 2015.
PED Outbreaks in Other Countries
In 2014, the PEDv was found to be causing disease outbreaks in Mexico, Colombia, Peru, Dominican Republic and Japan.
While there have been no reports of PED outbreaks in Latin America over recent months, losses from the disease continue to be reported regularly in Japan.
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