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A UK perspective: Porcine Epidemic Diarrhoea

14 June 2018

According to research, as few as 100 PED virus particles can cause an infection in pig herds, writes Michaela Giles, author and research scientist for the British government

Porcine Epidemic Diarrhoea (PED) is caused by a coronavirus called Porcine Epidemic Disease virus (PEDv), first named in 1978. Two different types are recognised: PEDv Type I only affects growing pigs whereas PED Type II affects all ages including sucking pigs and mature sows. Type I is seen as a low level endemic disease in the UK with pro-active surveillance only detecting very low numbers annually. Type II is a more virulent strain, also known as ‘highly virulent PEDv’, that has been causing outbreaks in Asia since 2010 and appeared spontaneously in the US in 2013-14 where it was responsible for the death of over 1 million pigs, with up to 100% mortality seen in piglets less than 7 days old.

All suspect PED cases are monitored by the Animal and Plant Health Agency (APHA) in England and Wales and by SAC Consulting Services (SAC) in Scotland. The government also provides funding to perform pro-active surveillance, for PEDv Types I and II, on any clinical submission presenting with diarrhoea.

The devastation of PEDv Type II in the US led the UK pig industry to look holistically at the welfare repercussions and the potential trade implications to the UK, should PEDv Type II enter the UK. The risks were assessed on the importation of both live pigs and pork products; the effect on our export market; and the possible impact on the genetic diversity of our rare breed pedigree herds. It was concluded by the Pig Health and Welfare Council (PHWC) that the UK required a workable contingency plan, formalising how the UK pig industry would work together to prevent and/or control the introduction of PEDv Type II. This was the first industry-led discussion, which included APHA, SAC, National Pig Association (NPA), British Pig Association (BPA), the Agriculture, Horticulture Development Board (AHDB) Pork and allied industries leading governments to introduce PED as a notifiable disease.

If you suspect PED in England and Scotland then you must now report it, this applies to all pigs including pet pigs. You must contact your vet or your local APHA/SAC office if your pigs show the following signs:

• Diarrhoea that spreads quickly in a group of pigs over a few days.
• 50% or more have diarrhoea.
• Death of 30% to 100% of young suckling piglets.
• Diarrhoea in older pigs is temporary and they recover.
• Diarrhoea tends to be watery.
• Reduced appetite, vomiting, lethargy.

You may also notice within breeding adults associated production losses such as: increase in returns to service if sows or gilts are affected in early pregnancy or abortion in later pregnancy; Agalactia in farrowed sows; and reduced libido in boars.

There are other diseases that may cause similar clinical signs, including; coccidiosis, transmissible gastroenteritis (TGE), rotavirus diarrhoea, Clostridium perfringens enterotoxaemia, and E. coli scours. The free testing service will determine if the clinical signs are caused by PEDv but will not test for other pathogens.

Unlike other notifiable diseases in pigs, there is no legislative requirement for official testing, culling, movement controls or other restrictions. Controlling the disease will be industry-led and desk based exercises have been performed to challenge the efficacy of the contingency plans. Importantly; under the new legislation, the APHA is legally permitted to inform the industry levy board, AHDB Pork, of all suspect cases. The AHDB Pork will use this information for the purposes of disease control, by providing veterinary and biosecurity advice, supporting the affected pig farm to control the disease on-farm thus limiting off-farm spread, and alerting other farms at risk.

How pig farmers are protecting the UK herds

The AHDB Pork has published a series of Standard Operating Procedures (SOPs) on preventing, containing, controlling and eliminating PEDv from our herds. As the only tools we have are strict biosecurity procedures, much of the advice centres on this, including how to keep PEDv out and what to do to contain a PEDv outbreak should one occur.

There are no licenced vaccines for use in the UK at present. These SOPs are linked with the published PHWC Contingency Plan and both are constantly updated as our virus knowledge increases and the geographical spread changes. The advice includes:

  • Using barriers to prevent disease spread, e.g. restriction of visitors, biosecurity procedures for essential visitors and the use of "No Entry" signs.
  • Effective cleansing and disinfection protocols.
  • Organising movement of people to prevent cross-contamination around the farm ensuring the disease is kept confined in one area.
  • Keeping records of all visitors and vehicles, plus incoming pigs so in the event of an outbreak, sources of infection or potential onward transmission routes are quickly identified.
  • Biosecurity advice to hauliers.

The incubation period is typically two to four days and so the first clinical signs are seen approximately four days after PEDv enters the herd. This is well within the recommended three to six weeks isolation of all new incoming stock and one of the most valuable tools in keeping the disease contained on-farm. If the isolation facility is outside, and cannot be effectively disinfected, then it should be noted before next use that the PEDv can remain infectious in the environment for up to a month, especially in cool, moist conditions.

To further assist keeping the UK pig herds free of PEDv Type II, the AHDB Pork manages a Significant Diseases Charter, to which PED has been included. The Charters’ aim is to share information on disease outbreaks quickly so that producers, smallholders or pet pig owners can be informed of an outbreak in their area and they can increase their biosecurity precautions appropriately. Signing of the Charter is voluntary but highly recommended as an important biosecurity tool. Early detection is key in assisting the prevention of spreading the disease.

To reinforce how important our biosecurity is in protecting UK pig herds – the infective dose of PEDv Type II has been researched and as few as 100 virus particles can cause an infection. To give you some idea of how small the infective dose is, you could fit approximately 20 million virus particles on the head of a pin, so it doesn’t take much contact with the faeces of an infected pig to cause disease.

 

Michaela Giles is consultant editor to The Pig Site, a post-doc research scientist for the government within the livestock health industry, and a member of the APHA Pig Expert Group. She writes for Practical Pigs magazine and for the AHDB Pork on small-scale pig production, and is a British Pig Association representative for the Southern region. Michaela’s first book The Commuter Pig Keeper was published in 2016.

Advice for producers & SOP links: https://pork.ahdb.org.uk/health-welfare/health/emerging-diseases/pedv/standard-operating-procedures
AHDB Pork PEDv pages: www.pedv.co.uk
PEDv Contingency Plan: https://pork.ahdb.org.uk/media/273229/contigency-plan-ped-22-aug-2016.pdf

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