Abstract

An outbreak of Porcine Epidemic Diarrhoea (PED) occurred in pigs in the summer and autumn of 2014 in the middle of the Ukraine.

The clinical outbreak resulted in a loss of six pigs per sow per year and took 20 weeks to resolve.

The virus identified 99.8 per cent similar to US strains. It is most similar to the PEDv KJ6456537.1 USA/Kansa29/2013, which have been isolated from the severe PED outbreaks in North America and Asia.

This is the first recognised detection of this virulent PEDv strain in Europe.

Introduction

An outbreak of PED occurred in the summer and autumn in the middle of the Ukraine. The source of the initial infection appeared to be an adjacent farm 1.5km from the index case.

Figure 1. The genetic tree of the PED KP403954 Ukraine/Poltava01/14 Virus

Farm Background

The farm practised weekly batches of 240 farrowing places – a 5,000-sow unit. A pig flow model of 300 a week to breed and weaning 3,000 piglets per batch. The model targets had been consistently achieved for over 18 months prior to the outbreak. The farm practised three-site production with nursery pigs leaving the farm at 27 days of age. The farm practises extremely good biosecurity precautions. Blood plasma was no included in the pig feed.

The farm was specific pathogen free to Porcine Reproductive and Respiratory Syndrome virus (PRRSv), Mycoplasma hyopneumoniae, Aujeszky’s disease, Brachyspira hyodysenteriae, Sarcopties scabiei var suis, toxigenic Pasteurella multocida, Gastroenteritis Virus and other OIE pathogens. There was no change in this specific pathogen status during or after the outbreak.

Clinical Signs and Diagnosis

The outbreak started in the afternoon of day 1 in a single farrowing sow 10 days post-farrowing. The sow presented with vomiting and profuse diarrhoea. Within hours, her piglets started to vomit and had profuse watery yellow diarrhoea. The vomiting and diarrhoea then spread throughout the farrowing room and adjacent houses.

Figure 2. Index sow with feed refusal, profuse diarrhoea and vomiting. Her 10 day-old piglets were vomiting and dying.

Figure 3. Piglets at all ages started to vomit and have profuse diarrhoea. The piglets less than 10 days of age became visibly dehydrated within hours

Figure 4. The piglets huddle and many choose to lie on their recumbent mother

Figure 5. Mortality rates are 100 per cent in piglets less than 10 days of age

A presumptive diagnosis of PED was made the following morning following clinical examination of the farm and postmortem examination of the piglets. Postmortem examination demonstrated a thin walled small intestine with very little gross congestion. Intestinal histopathology showed lesions consistent with a viral aetiology. The presence of PEDv was confirmed by rt-PCR examination of faeces and intestinal contents.

Figure 6. Few gross postmortem findings outside the intestinal tract

Figure 7. Small intestines are thin-walled and fluid filled with minimal signs of congestion

Figure 8. Histopathology of the jejunum of a seven-day-old piglet, revealing severe villus atrophy.

Figure 9. PED-positive response in an on-farm lateral flow device. Note: TGE-negative.

Virus Identification

Samples were sent to the Animal and Plant Health Agency, Weybridge, UK, where the virus was also confirmed as PED virus by PCR. A portion of the S gene of the virus was sequenced. The sequence showed the virus to be related to the Chinese/USA PED virus strains, which have caused severe losses in both Asia and the USA. The virus is similar to the KJ6456537.1 USA/Kansa29/2013 and the KF177258.1 China/YJ7C/2012.

This is the first recognised detection of this virulent PEDv strain in Europe.

The virus is being further sequenced to complete the investigation.

Progression of the Clinical Problem

Piglets less than 10 days of age

To minimise the suffering of neonatal piglets, piglets less than 10 days of age were euthanased.

Piglets older than 10 days of age

Piglets older than 10 days of age were very sick but generally survived. Pre-weaning mortality rates of 25 per cent were not uncommon.

Various oral anti-diarrhoeal treatments were attempted including charcoal, loperamide and kaolin. Given the scale of the outbreak, the most successful palliative treatment appeared to be the charcoal, which the piglets and weaners ate voraciously. Electrolytes and other supportive therapies were provided.

Nursery pigs

Pigs at 27 days of age had to be weaned and were then moved to the off-site nursery. Within a week, older pigs in adjacent rooms developed clinical signs of vomiting and diarrhoea.

Seven days post-infection, the majority of the nursery pigs recovered their appetites and diarrhoea stopped. The weaker nursery pigs were slower to recover. Despite having no clinical signs, virus was still found by rt-PCR 30 days post-recovery in the weaker pigs. Mortality in early-weaned pigs which demonstrated PED exceeded 20 per cent at times. In general, post-weaning mortality doubled.

Adult pigs

Exposure of sows to faeces from infected piglets was initiated on day 1 and this obviously contributed to the spread of the clinical signs in adults.

Within three days, the adults recovered their appetites and diarrhoea stopped. An abortion in sows, 20 to 30 days of pregnancy occurred following the outbreak and feedback programme. This was not associated with the pyrexia (raise in body temperature). The loss of piglets in the early part of lactation resulted in enormous disruption to the weekly batching breeding programme.

Mortality in sows was low, however, a spike in sow mortality of 0.3 per cent increase, was associated with the first two weeks of the outbreak. The loss of feed and general lethargy of the gilts resulted in disruption of their oestrus cycles.

Figure 10. Vomiting and diarrhoea occurred in all the age groups within 10 days of the initial outbreak

Figure 11. Abortion in sows 20 to 30 days of pregnancy was recorded in 30 per cent of the pregnant sows.

Summary of the Clinical Problem

The clinical problem can be illustrated by the impact of the PED outbreak on the pig flow. This method of graphically monitoring pig production, provides a visual prediction to the farms performance and links in real-time breeding; farrowing; weaning and ultimately finishing.

Figure 12. Pig flow impact of PEDv on a farm practising weekly batching

The above graph illustrates the production on the farm, based on the farm’s batching pig flow model. The farm’s pig flow model is a weekly batch system with 300 sows to breed, 240 sows to wean and 3,000 piglets to wean per weekly batch.

The batch number corresponds to the week’s number. The infection started in batch 27, thus killing piglets conceived in batch 10 (115 days previously).

Control Measures

Various procedures were implemented.

Day 1:

• Euthanasia of all piglets less than 10 days of age.
• At the initial outbreak weaning of all piglets more than 10 days of age.
• Removal of intestines from dead sick piglets and nursery pigs. This material was used to make an autogenous vaccine by feedback to the gilts and sows.
• When making the autogenous vaccine ensure that the meat grinder does not get too hot which can kill the virus. Do not add chlorinated water to the 'soup' as this may destroy the virus.

Over the next few weeks:

• The euthanasia of all piglets for the next three to four weeks, at birth.
• Provide feedback material to all adult sows: 10ml of intestine contents per sow for three occasions, three days apart.
• Check the feedback material contains the PED virus using a lateral flow device.
• Repeat feedback programme in three weeks.
• The feedback programme then continued for sows six and three weeks pre-farrowing.
• Place sufficient intestine contents in a freezer to allow for a minimum of 18 weeks of feedback materials.
• Use of charcoal to nursery pigs to provide an anti-diarrhoeal treatment.
• Sows reproduction and cycling needs to be controlled using altrenogest and a rational breeding programming.
• Staff and equipment movements around the farm need to be curtailed. All contact between different departments need to stop, especially once the farm starts producing piglets again.
• Staff to wear clearly different clothing, boots and gloves between departments.
• Disinfect and lime wash all passageways and any equipment.
• Practise strict all-in/all-out and batch production.
• Once piglet production starts again, stop all processing until 10 days of age, including iron injection.
• Do not enter the farrowing pen, unless absolutely necessary and then disinfect boots.
• Stop all cross-fostering.

Rationale

• Produce consistent anti-PED colostrum from immunised sows. But note this may only last 10 weeks. Subpopulations and poor persistence of immunity in sows is a serious problem.
• Reduce viral load on the farm by euthanasing affected newborn piglets.
• The virus alone will die out on the farm within a couple of weeks
• Virus excretion by weak pigs may occur up to 35 days post-infection.

Staff

Counselling and discussion was important for all staff involved in this outbreak. The impact on human emotion cannot be over-emphasised.

Long term

Once the farm has stabilised and is producing normal weaners, destroy the remaining feedback material in the freezer, removing any remaining virus on the farm.

Figure 13. Thorough farm internal biosecurity with lime-washing of passageways and complete separation of farm teams, was required to contain the outbreak.

Figure 14. The farrowing area illustrating the hygiene extremes required to control the spread of the virus from one batch to the next.

Impact of the Outbreak

Performance took 20 weeks to return to a semblance of normality.

A total of 30,000 piglets were lost in this outbreak. This equated to a loss of six weaned pigs per sow per year.

The impact on the welfare and well-being of the stockpeople was a major concern for the company with the loss of so many piglets, the need to euthanase and post-mortem such large number of pigs. It is essential to be concerned for the mental health of all stockpeople working on the farm.

Acknowledgement: The team is extremely grateful for the assistance of the Animal and Plant Health Agency, Weybridge, UK, in sequencing the virus strain and the Center of Veterinary Diagnostics, Ltd, Ukraine, for carrying out the PCR, serology and histopathology.

Further Reading

Go to our previous news item on this story by clicking here.

February 2015