SCIENTISTS have shown for the first time that stress makes pigs more likely to suffer from a disease which costs UK farmers millions of pounds a year.

The findings from the Royal Veterinary College (RVC) could influence the conditions that pig herds are kept in to reduce the likelihood of disease outbreaks.

The researchers were investigating the causes of a complex group of pig diseases known as PCV-associated diseases (PCVAD), which can lead to diarrhoea, wasting, respiratory distress and death.

All of these have infection with porcine circovirus (PCV) 2 as a common underlying factor and this costs UK farmers tens of millions of pounds a year.

It has always been assumed that the development of PCVAD needs PCV2 and a secondary infection for symptoms to occur.

However, for the first time, the researchers showed that environmental stress from higher temperatures, crowding, or both, can induce symptoms attributed to PCVAD without any secondary infection.

PCV2 infected pigs kept in above comfort temperatures, or kept in pens smaller than current minimum guidelines, were more likely to show reduced weight gain and had higher viral loads than those kept in cooler temperatures or larger pens. These risk factors can occur in herds in the UK.

Prof Dirk Werling, from RVC, who led the project, said: "We are confident that our findings have a really big impact for the pig industry, given the fact that PCV2 is so common.

"These findings clearly indicate that in addition to vaccination against PCV2, changes in the current farming systems can only be achieved in the long term through a more sustainable agricultural approach, which would involve a less stressful rearing of animals for food consumption. As customers increasingly prioritise good conditions for livestock, pressure on farmers to produce as cheap and fast as possible might reduce."

The study, published in Veterinary Microbiology was funded by the Biotechnology and Biological Sciences Research Council, with contributions from Bpex, Biobest Laboratories and Zoetis Animal Health.