Environmental stress such as high temperatures and crowding can cause Porcine CircoVirus Associated Disease (PCVAD) symptoms in pigs without secondary infections, according to scientists.

The study could have a big impact on the pig industry

Researchers investigating the causes of PCV-associated diseases (PCVAD) which can lead to diarrhoea, wasting, respiratory distress and death, and costs UK farmers millions of pounds a year, found the common underlying factor was infection with porcine circovirus (PCV) 2.

It had been assumed that the development of PCVAD needed PCV2 and a secondary infection for symptoms to occur.

However, research showed, for the first time, that environmental stress caused by higher temperatures, crowding, or both, could induce symptoms attributed to PCVAD without any secondary infection. PCV2 infected pigs kept in pens above the comfort temperature or in pens smaller than current minimum guidelines, were more likely to show reduced weight gain and have higher viral loads than those kept in cooler temperatures or larger pens. The risk factors can occur in herds in the UK.

Project leader Professor Dirk Werlin said: “Within the initial part of this project, we identified specific risk factors on farms that had an impact on disease severity. We were able to confirm that these risk factors really contribute to severity of clinical signs under experimental conditions.

“These findings clearly show that sub-optimal management will have further impact on economic losses. We are confident that our findings will have a really big impact for the pig industry, given the fact that PCV2 is so common.

“The 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 (BBSRC) ‘Combating Endemic Diseases of Farmed Animals for Sustainability (CEDFAS) initiative, with contributions from BPEX, Biobest Laboratories and Zoetis Animal Health.

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