Scientists investigating PEDv (Porcine Epidemic Diarrhoea Virus), which between its discovery in May 2013 and July 2014 had infected an estimated 50 percent of the US swine breeding herd, believe they have made a promising discovery in the battle against the disease.

Though older pigs generally survive infection with PEDv, the virus attacks the gut of piglets, preventing them from absorbing fluids and causing them to die of dehydration. Since its discovery in the US 'Hog Belt', the virus has also spread to Canada and Mexico, leading the EU to take protective measures in May last year.

A team from the University of Minnesota discovered that the piglets of sows exposed to a mild form of the disease had a much better survival rate compared to those born to sows who had no prior exposure to PEDv. 100 percent of the piglets whose mothers had been 'immunised' survived, compared to 67 percent of those whose mothers had no exposure.

This, they said, shows two things: that immunity to a milder form of the disease can protect against more virulent PEDv, and that immunity in sows can be passed on to their offspring.

Over the winter, outbreaks of PEDv have been limited, leading some of the US farm press to suggest that the pig sector is 'gaining on' the virus. However, this pattern of relative dormancy was also seen over winter a year ago, before the number cases skyrocketed in spring 2014, and there are still no harmonised measures in place to deal with the disease.