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Porcine Endemic Diarrhoea – An Emerging Threat

01 August 2016, at 12:00am

All OVs should be aware of the potential threat of a virulent strain of Porcine Epidemic Diarrhoea, and the clinical signs they should be vigilant for. Since the OV conference in October 2015, PED has been made notifiable in England and Scotland, although with differences from other notifiable diseases as described below.

Virulent porcine epidemic diarrhoea virus (PEDv) emerged in North America from May 2013, causing epidemic outbreaks of diarrhoea with high mortality in young piglets.  In the US, there was an estimated 7-8 per cent shortfall in pigs for slaughter and more than seven million piglet deaths in the US by early 2015.  Infection is believed to have entered the US pig herd from Asia where virulent strains have also spread in recent years, although the exact route of introduction to the US remains uncertain.

Virulent PEDv represents an emerging threat to pig health and welfare, and to food security, by affecting pork production.  It does not affect humans or have any food safety implications, and other livestock species are not affected. Learning from successful control in Canada, preventing introduction of PEDv onto UK pig farms, and ensuring prompt detection should it enter, requires collaboration and ongoing communication between all the stakeholders involved and OVs, of course, have a key role to play.

Following public consultation and dialogue between Defra and industry, PEDv was made a notifiable disease in England in December  2015, albeit with significant differences from traditional notifiable diseases of pigs. Under this legislation, there are two main requirements:

  1. Pig-keepers or their veterinary practitioners are obliged to inform the APHA of suspect and confirmed cases of PEDv in their pigs.
  2. APHA is legally permitted to inform the appropriate industry organisation (AHDB Pork) in confidence, of the details of suspected and confirmed cases of PEDv, so that they can provide targeted advice to enable pig keepers, their vets and allied industries, to take disease control measures.

In March 2016, Scotland followed suit, by reporting there to Quality Meat Scotland (QMS) via the Scottish Pig Disease Control Centre. OV briefing notes were issued giving details on both occasions (http://ahvla.defra.gov.uk/documents/ov/Briefing-Note-1615.pdf" class="redactor-linkify-object">http://ahvla.defra.gov.uk/docu... and http://ahvla.defra. gov.uk/documents/ov/Briefing-Note-0416.pdf).  

The main reason for making PEDv notifiable is to enable industry to assist affected premises and those at risk as soon as possible after the disease is identified to control the disease, limit the spread of infection, and so increase the likelihood of eliminating the spread.  

Unlike other notifiable diseases, there would be no legislative requirement for official testing, culling, movement controls or other restrictions, and the control of disease would be industry-led with no action from government, beyond taking notifications and sharing information with AHDB.  

There is much good work going on to address the threat of PEDv to the UK pig industry. Ensuring prompt detection of PEDv should it infect pigs here relies very much on those on the front line; that is, pig keepers and veterinary surgeons with clients who keep pigs, which includes many OVs. 

You are the eyes and ears of surveillance for PEDv and can play your part particularly by:

  • Encouraging your clients who keep pigs to take measures now to minimise the risk of diseases being introduced to their premises and pigs. PEDv is an exotic disease risk, but there are endemic pathogens which they should also take measures to keep out, and so safeguard the health of their pigs. Notably, these include swine dysentery and porcine reproductive and respiratory virus. There is advice on biosecurity on this link: http://pork.ahdb.org.uk/pig-pr... biosecurity/ and some targeted at smallholder herds on this link: http://pork.ahdb.org.uk/pig-pr... smallholders/
  • Making sure that you and your pig-keeping clients are familiar with the clinical signs of PEDv,  the key features of which are:
  • Diarrhoea which spreads rapidly in a group of pigs over a few days.
  • High proportion of pigs in a group developing diarrhoea (50 per cent and more).
  • High mortality (30-100 per cent) occuring in young sucking piglets, if due to a virulent strain of PEDv.
  • The disease can affect any age of pig.
  • The diarrhoea tends to be watery.
  • Diarrhoea in older pigs is transient and they recover.  
  • Sometimes pigs also show reduced appetite and lethargy and may vomit.
  • If you suspect an outbreak of PEDv, the attending vet or pig keeper is now legally obliged to report this to APHA for pig premises in England, or QMS for those in Scotland. There is guidance on reporting PEDv on Government and AHDB Pork websites: https:// www.gov.uk/guidance/porcine-ep... and http://pork. ahdb.org.uk/media/74694/ped-2-reporting-ped-outbreaks-v3.pdf.
  • After reporting the disease, it is important to progress testing of faecal samples from affected pigs for PEDv promptly, so that the disease can be confirmed or ruled out. Guidance on sampling suspect PED outbreaks and accessing testing at APHA is provided on the AHDB website: http://pork.ahdb.org.uk/media/...
  • It’s also important to immediately take appropriate actions to prevent the spread of infection from the premises, while waiting for test results – there is information about what to do in the contingency plan on the AHDB Pork website, and suspected and confirmed PED cases will be offered advice.

Faeces from young piglets infected with virulent PEDv strains contain very high concentrations of virus. This means that infection spreads readily through contact with infected pigs or anything contaminated with their faeces through faeco-oral transmission, with pig transport vehicles significantly implicated in the spread of PEDv after its introduction to North America.  

Experience there has shown that implementing stringent biosecurity measures, detecting clinical outbreaks promptly, and maintaining good communication and cooperation between the various industry, veterinary, government and laboratory partners, are key to controlling the spread of infection.  

The pig industry and other stakeholders have taken this on board, and Defra and APHA have been working in close partnership with the pig industry, pig veterinary community, allied industries, SAC CVS, and the Welsh and Scottish Governments to reduce the risk of PEDV entering the UK, ensure rapid detection of disease should it enter and infect pigs, and develop an industry-led contingency plan for PEDv control here in the UK.

This plan can be found here: http://pork.ahdb.org.uk/media/...

APHA provides diagnostic PCR testing for PEDv and suspect PEDv cases are tested rapidly. PEDv has not been diagnosed in the UK since 2002, but strains of PEDv have been causing outbreaks in several European Union member states since 2014. Though to date, the virulent strain has only been identified in the Ukraine in Europe.  

As additional surveillance, non-suspect cases of diarrhoea in pigs in England and Wales, from which samples are submitted to APHA for diagnostic testing for other causes of diarrhoea, are tested for PEDv on a weekly basis.  Over 400 submissions tested negative for PEDv between June 2013 and May 2016.

This gives added assurance that PED outbreaks are not being missed, especially as diarrhoea is a common sign in pigs, although PEDv outbreaks have some distinctive features as outlined above. At present, testing is performed without charge to the submitting vet or pig keeper. o