Gene-Edited Pigs Resistant to Swine Fever: A Potential Advancement for Animal Welfare

By making a few genetic modifications, pigs can be rendered entirely resistant to swine fever, a significant issue for farmers globally. This gene editing could also confer resistance to related viruses in cattle and sheep.

The widespread adoption of gene-edited pigs resistant to swine fever is expected to enhance animal welfare, boost productivity, reduce greenhouse gas emissions, and lower retail prices. “This will foster sustainable livestock production and promote the well-being of pigs,” asserts Helen Crook from the UK Animal and Plant Health Agency.

Swine fever is a highly contagious viral illness that can lead to symptoms ranging from fever to diarrhea and miscarriage, often resulting in significant pig mortality.

While the disease has been eliminated in many regions, it can resurface. For instance, in 1997, the Netherlands culled 6 million pigs to contain an outbreak, and Japan has faced ongoing challenges since 2018.

Typically, when outbreaks occur, livestock are protected using vaccines containing live, weakened virus strains, which is a complex and costly process. “Vaccination demands extensive coordination and oversight,” mentions Christine Tate-Burkard from the University of Edinburgh, UK.

Countries utilizing vaccinations face restrictions when exporting to disease-free areas. Interruptions in vaccination programs can also lead to outbreaks, as seen recently in the Philippines, explains Tate-Burkard.

Nevertheless, the classic swine fever virus has a vulnerability. The viral protein bundles formed from long chains of amino acids must be cleaved into functional pieces, relying on specific pig proteins for this process.

By altering a single amino acid in this pig protein, referred to as DNAJC14, it may be possible to obstruct this cleavage. Tait-Burkard and colleagues employed CRISPR gene editing to create pigs with this minor modification.

Subsequently, the team sent some of these pigs to a secure facility, where Crook’s group introduced the live swine virus intranasally. All typical pigs fell ill, while the gene-edited pigs showed no signs of infection. There were no symptoms, antibodies, nor detectable virus.

“These pigs demonstrated complete resistance to viral replication and remained healthy and content throughout the experiment,” states Crook.

This research was partially sponsored by Genus, a major international breeding company currently evaluating the commercialization of these pigs.

Genus has previously developed gene-edited pigs resistant to another significant disease, porcine reproductive and respiratory syndrome, which are already approved in the United States, Brazil, and other nations. The company awaits approvals in Mexico, Canada, and Japan—key export markets for the U.S.—before it can start selling semen to farmers.

When used to implement small changes that can naturally occur, gene editing often faces less stringent regulations compared to traditional genetic engineering. Japan has already sanctioned three types of gene-edited fish.

The UK is anticipated to begin approving gene-edited plants soon, although regulations for livestock are yet to be finalized. It is expected that these regulations will prioritize animal welfare.

The research team observed no adverse effects in the swine fever-resistant pigs, according to Simon Lillico and colleagues from the University of Edinburgh, although further research is necessary to confirm these findings.

He emphasizes that traditional breeding lacks such welfare considerations. “It would be beneficial to ensure a level playing field,” he remarks. “We are aware that some conventionally reared animals experience low welfare standards.”

A virus closely related to classical swine fever is responsible for causing bovine viral diarrhea in cattle and borderline disease in sheep. While these diseases are not lethal, they still impact welfare and productivity. The Edinburgh research team is presently examining whether modifications made to pigs will also benefit cattle and sheep.