Farming is poised for a gene editing revolution that could overcome some of the world’s most serious livestock diseases, the UK’s top animal scientist has said. Prof Eleanor Riley, director of the Roslin Institute in Edinburgh, said new techniques will soon allow breeders to genetically engineer disease resilience and, in some cases, immunity into pedigree animals, saving farmers millions of pounds a year. “Genes can be modified to massively increase resistance and resilience to infection,” she said. “The health and welfare benefits of this could be enormous.” Roslin, one of a handful of sites in the world with the capacity for both gene editing and running animal trials, recently announced it had made pigs that appear to be completely immune to Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), also known as blue ear disease, which costs the swine industry £120m a year in pig deaths and expensive biosecurity. In a separate trial, Roslin is testing pigs designed to be resistant to African swine fever, a highly infectious disease that has recently swept across the Baltic countries and into Poland, causing alarm among farmers. Riley, who took over as director in September, said the PRRSV-resistant pigs could be approved for use on farms within three to five years, if a trial that has just finished involving a dozen pigs confirms the animals are immune. The disease causes breathing problems and leads to stillbirths and stunted offspring when sows are infected. “Globally this is the most significant pig disease,” Riley said. The advance came after scientists identified the pig gene that encodes the receptor on the surface of cells that the virus binds to to gain entry. By removing a tiny section of this gene, this doorway for the virus to enter cells is removed, and initial trials suggest the pigs made at Roslin are entirely resistant to PRRSV. The work has been done in partnership with a livestock breeding firm called Genus PIC (Pig Improvement Company), whose pedigree herd seeds about 30% of the world’s pigs. Prof Mark Stevens, director of research at Roslin, said Genus is now preparing – should the final results support the move – to introduce the edit into their elite herd. “That’s the great advantage of partnering with some of these big breeders,” he said. “If you get it right, they can implement the gain on a vast scale.” The latest trial results are expected to be published shortly, but it would take several years and several generations of breeding to comprehensively introduce the edit into pedigree stock. “Being able to edit these pigs and make them resistant to infection holds a huge amount of promise,” said Prof Stevens. “But it’s not going to be any time soon that you eat one.” Scientists at Roslin have also identified a target gene that could confer resistance to avian flu, which is normally fatal for chickens, but which crows and ducks are fairly resilient against. “In outbreaks it’s not uncommon for a farmer to close the door to an apparently healthy flock and open the door the next morning to find 99% of the birds dead,” said Stevens. “But that high mortality actually provides an opportunity to look at what’s genetically different about the one bird that’s still standing.” Roslin is also investigating the genetic basis of resilience against E coli and campylobacter, which is estimated to cause about 500,000 cases of human food poisoning in the UK each year. In fish farming its scientists are tackling the oyster herpes virus, and amoebic gill disease in atlantic salmon, which is currently dealt with by eradicating sea lice using powerful chemicals, sometimes in open water. Riley said there are signs that public opinion has warmed towards the acceptability of genetically engineered animals since the possibility of GM food first emerged in the 1990s. “The feeling is, cautiously, it seems as though public opinion is slowly coming around to the idea,” she said. In part, the technology is different. Modern gene editing is far more precise, making unanticipated side effects much less likely. In some cases one letter in the genetic code is switched, in others a tiny bit of DNA is removed. “There’s nothing foreign introduced,” she said. There is also a powerful incentive to use the technology to improve animal welfare and lessen the environmental impact of livestock farming, which makes a major contribution to the world’s carbon emissions and deforestation. Riley dismissed the idea that the current trend towards veganism and eating less meat in the west would make a major contribution to solving these issues in the near future. “It’s the very much the definition of a first world problem,” she said. “If you went to a supermarket in a working class district of Manchester or Liverpool or the East End of London and said people are eating less meat, they’d say ‘What on earth are you talking about?’” In developing countries, she added, there is no immediate prospect of being able to replace the nutritional benefits of meat with high quality plant-based proteins. “An egg a day can transform the life of an African child from being a child that’s stunted, starving, malnourished and doesn’t have a future to a child that grows and thrives and goes to school,” she said. “As a race we may one day decide [to be vegan], but in the interim we’ve got a big problem with sustainable livestock production.”
Scientists have developed gene-editing techniques that will soon enable breeders to produce animals that are resistant or immune to serious livestock diseases. The Roslin Institute in Liverpool has successfully produced pigs that were resistant to The Roslin Institute and Porcine Reproductive (PRRSV), and if current trials go to plan, PRRSV-resistant pigs could be approved for farms in three to five years . Scientists at The Roslin Institute are also trialling avian swine-fever resistance, as well as investigating avian flu and the genetic basis of resilience against E coli and campylobacter.