Scientists have used CRISPR to edit a single gene in pigs, making them fully resistant to classical swine fever, a contagious disease that devastates livestock. This breakthrough could enhance animal welfare, boost productivity, and reduce emissions. The same edit may protect cattle and sheep from related viruses.
Classical swine fever, a highly contagious viral disease, causes fevers, diarrhoea, miscarriages, and high mortality in pigs, severely impacting farmers worldwide. The disease has been eliminated in many regions but re-emerges periodically; for instance, six million pigs were culled in the Netherlands in 1997 to contain an outbreak, and Japan has struggled to eradicate it since 2018. In areas where it persists, live vaccines are used, but they are laborious, expensive, and prevent exports to disease-free countries. A recent disruption in vaccination efforts led to an outbreak in the Philippines.
Researchers at the University of Edinburgh, led by Christine Tait-Burkard, identified the virus's vulnerability: it depends on a pig protein called DNAJC14 to process its proteins. By using CRISPR to alter a single amino acid in this protein, they created pigs that block viral replication. In tests at a secure facility run by the UK's Animal and Plant Health Agency, edited pigs exposed to the live virus via nasal spray showed no symptoms, antibodies, or detectable virus, remaining healthy throughout. In contrast, unedited pigs fell ill.
"These animals were completely resistant to replication of the virus and remained happy and healthy throughout the study," says Helen Crooke at the agency. The work, partly funded by breeding company Genus, suggests benefits for sustainable production. "It would help towards sustainable livestock production, and with nice healthy, happy pigs," Crooke adds. Widespread adoption could lower greenhouse gas emissions and food prices.
Genus, which has commercialized gene-edited pigs resistant to porcine reproductive and respiratory syndrome—approved in the US and Brazil—is considering this new edit. Regulatory landscapes vary: many countries treat small, natural-like edits leniently, with Japan approving three gene-edited fish. England plans to approve gene-edited plants soon and is finalizing livestock rules, emphasizing welfare. No adverse effects have been observed in the edited pigs, though further studies are needed, says team member Simon Lillico. "A level playing field would be lovely," he notes, highlighting welfare issues in conventionally bred animals.
The team is now testing if the edit works against related viruses causing bovine viral diarrhoea in cattle and border disease in sheep, which affect welfare and productivity despite being less lethal.