A look at the virus that Threatens pig farming

BY EILIDH CORR, QUALITY MEAT SCOTLAND, AND JILL THOMSON, SRUC VETERINARY SERVICES

Porcine respiratory and reproductive syndrome (PRRS) virus is widely considered to be the most economically-significant disease of pigs in Scotland.

The virus causes a spectrum of problems, from reproductive failure in sows to pneumonia in growing pigs. It also suppresses the immune system, leaving infected pigs vulnerable to other conditions. These features combine to cause widespread impacts on the productivity, efficiency and welfare of the herd.

PRRS infection predisposes the herd to other disease, and so its presence has a disproportionately-large impact on animal health.

Indeed, a multinational study analysing data from farms across Belgium, France, Germany and Sweden reported higher use of antibiotics in farms vaccinating against several pathogens, including PRRS.

Another study reported similar findings in Denmark, with vaccination against PRRS being associated with higher antimicrobial use (AMU). The authors also reported that “vaccination against PRRS and higher AMU were associated with increased lean meat percentage, potentially due to disease outbreaks resulting in reduced growth, and lower carcass weight at slaughter in herds with PRRS”.

In Scotland, most units classed as “positive” are controlling the virus using vaccination – so based on these studies, there is reason to believe that these units may use more antimicrobials than a negative herd would require.

Though the association between vaccination and AMU may appear contradictory, it must be noted that most farms only vaccinate once that disease is already circulating.

The true impact of uncontrolled PRRS virus on AMU is anticipated to be several times greater.

Efforts to combat the development of antimicrobial resistance are focused on reducing avoidable use of antibiotics.

The UK pig industry has reduced its Global Warming Potential by 3537% in the last 18 years. Control of endemic disease over this period has been central to achieving such advances, and potential exists to go significantly further by controlling or even eradicating PRRS virus in Scotland.

As African swine fever marches across Europe, with Italy’s recent cases being found hundreds of miles from the previous confirmed outbreaks in Germany, we are reminded that biosecurity and vigilance are our only defences against this devastating disease.

INSIDIOUS: The porcine virus PRRS is the cause of numerous problems in pig herds, including pneumonia and reproductive issues, and – devastatingly – it leaves affected herds very vulnerable to other diseases. PRRS virus is controlled with vaccination, but Scotland could potentially go further by attempting to eradicate the disease.