Preventing Subclinical PCVD through Piglet Vaccination

"In the region where I work, the performance on fattening units had not improved over the last five years, with an average mortality of 2.5 per cent," explained Cees Veldman, pig veterinarian from the Netherlands.

However, he cited four case studies demonstrating that the implementation of piglet vaccination with Circovac® can offer farmers significant benefits.

In the first example, he said that the mortality on a 740-sow, 7,600-fattener unit, was more than 3.5 per cent during the second half of the fattening phase with an average daily weight gain of 770 g. There was no mixing of pigs in the first three days of life.

Vaccination of the pigs against pleuropneumonia improved the situation for three months. Piglets were vaccinated with Circovac at eight weeks of age, explained Dr Veldman, which cut mortality by 50 per cent and reduced antibiotic use by a spectacular 35 per cent.

"This met the very strong demand for our Dutch consumers," he stressed.

In another example, he said that on a multiplier 1,400-sow farm that sells piglets to off-site fattening units, respiratory disease and meningitis affected weaners (between four and 10 weeks of age) and mortality reached four to 10 per cent in the fatteners.

In October 2008, sows and piglets were vaccinated with Circovac – the piglets at six weeks of age – which produced a quick improvement in fattening.

"Also, mortality dropped from 13 to nine per cent pre-weaning and from 3.5 to 2.5 per cent after weaning.

"Our target is to switch to sow vaccination alone within four or five months," said Dr Veldman.

Gaining Control of PCVD on Finishing Units

"Late stage – or endemic PCVD, as we call it – occurs in 60- to 80-kg pigs. We see typical wasters, and also many pneumonia," said Jake Waddilove, UK pig practitioner.

He presented four case studies where PCVD was acutely present in fattening, with different clinical expressions, including granulomatous enteritis.

On a 200-sow farrow-to-finish operation, PCVD had been present for seven years. Ileitis had been diagnosed but remained out of control after Lawsonia vaccination, he said.

The implementation of sow vaccination with Circovac was followed by what Mr Waddilove described as a "dramatic reduction" in the incidence of scours. Tylosin medication was withdrawn without any adverse effects.

As on the three other farms, a comparable reduction in antibiotic use was carried out.

In a 4,000-place finisher herd where severe respiratory outbreaks after 45 kg of bodyweight were the rule, average mortality fell from more than two per cent to less than 0.5 per cent as the Circovac-vaccinated progeny came through, and total medication costs dropped from 36 pence per pig to less than three pence.

"We are starting to get a hold of PCVD in finishers. It appears that sow vaccination can have a real impact on the levels of PCVD in finishing herds, while allowing reduced antibiotic use," concluded Mr Waddilove.

Three Circovac Vaccination Strategies Compared

An outbreak of post-weaning multisystemic wasting syndrome (PMWS) occurred in November 2007 on a farm of the biggest and most influential pig producer in Poland, reported Zygmunt Pejsak of the Institute of Pulawy in Poland.

Sows were inseminated weekly, 110 sows per batch. Before the outbreak, the farm produced an average of 19.9 piglets per sow per year – a good level of efficiency, Dr Pejsak said.

However, the fattening units were managed with a continuous flow and with very high density. The infection pressure was challenging, he said, with PCV2 and the main bacterial pathogens present.

When PMWS emerged, it caused up to 35 per cent losses from birth to slaughter but mortality averaged 28.8 per cent.

The owner of the farms wanted to compare different vaccination strategies so a control group was made with the progeny of six batches of sows born before PMWS.

In December 2007, six batches of sows and the same number of batches of piglets (from unvaccinated dams) were vaccinated.

Furthermore, in six batches, both sows and progeny were vaccinated – the piglets at seven weeks of age.

Before PMWS, the average mortality from birth to slaughter was 17.3 per cent, according to Dr Pejsak. During PMWS, the mortality rate reached 28.8 per cent. In the group where the sows were vaccinated, mortality was significantly decreased to 16.9 per cent. In the group where the piglets were vaccinated, mortality was 16.1 per cent and where both the sows and piglets had been vaccinated, it was 15.4 per cent.

"The best average daily weight gain was in the group where both sows and piglets were vaccinated (656 g per day), compared to 611 g per day before PMWS," he said, adding that average daily weight gain was around 636 g per day for the other two groups.

"In all vaccinated groups, PMWS proved successful up to the end of the fattening period," said Dr Pejsak.

Vaccination Boosted Live-Born Piglets

The farm described in the case study presented by pig practitioner, Julien Avon, is located in one of the area of France with the highest concentration of pigs.

The 140-sow farrow-to-finish farm, managed on an 'all in, all out' basis, had a chronic health problem in weaners.

"Eighty per cent of piglets had ear necrosis, and a chronic cough syndrome, which was contained with injectable long-acting antibiotics. The post-weaning mortality rate was up to three per cent – well above the maximum tolerable level of two per cent," explained Mr Avon.

In November 2007, the farmer consulted the veterinarian because of rates of six per cent mortality and 19 per cent morbidity in seven-week-old piglets, five per cent of which also showed wasting.

The case was handled with antibiotic supplementation "which proved to be a complete failure," explained Mr Avon.

The laboratory tests provided evidence only of swine influenza virus infection in the lungs, which did not help.

Mr Avon said: "The vet I was became desperate at this point. I deduced that the clinical pattern was caused by an immune disorder, which could be overcome by vaccination."

The new strategy was implemented in March 2008. Piglets were vaccinated with Circovac at weaning (three weeks of age), while sows were also vaccinated.

Mr Avon explained that piglet vaccination produced a reduction in the clinical signs to a light respiratory syndrome leading to a mortality rate of less than two per cent, and ear necrosis ceased.

From May 2008 onwards, the farm was only practising sow vaccination and the improvements have been maintained.

"But we also observed an unexpected result: the number of live-born piglets per litter levelled out at 13.5 – a gain of 0.8 piglets per litter," said Mr Avon.

"For me, the health status of a vaccinated sow herd is superior to that of an unvaccinated sow herd," he concluded.

Review of Relationship between PCV2 and Reproduction

Thaïs Vila presented an extensive literature review on the effects of PCV2 on reproduction.

"Published data confirm that PCV2 is shed intermittently in semen of naturally infected boars. This seems to be age-related," she said.

The literature also reveals that PCV2 in semen may be infectious. However, the minimum infectious dose is unknown.

"Nor is the effect of [off-label] boar vaccination on this shedding," explained Ms Vila.

In the female reproductive tract, embryos become susceptible as soon as the zona pellucida is ruptured. Such infections can lead to early embryonic death and abortion.

Foetuses are sensitive to PCV2 during the whore duration of gestation. The foetal myocardium is an elective target for PCV2 replication, which makes the heart the organ of choice for the diagnosis of PCV2 disorders, explained Ms Vila.

She concluded her presentation that numerous publications report naturally occurring reproductive failures linked to PCV2, mostly in newly established herds, when introduced gilts are naïve to PCV2 infections.

Further Reading

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Find out more information on Post-Weaning Multisystemic Wasting Syndrome (PMWS) by clicking here.

December 2009