Pigs with a Genetic Advantage: CRISPR and the End of Blue Ear in Livestock

Wednesday - March 13 2024, 10:09 UTC - 8 months ago

The PRRS virus has been a major problem for pig farmers for over three decades, causing high financial losses and health issues in pigs. However, a new generation of CRISPR-edited pigs immune to the virus has been created, offering a potential solution to the problem. These genetically diverse pigs bred for consumption were successfully tested and are seeking FDA approval for widespread distribution.

Many of us appreciate a juicy pork chop or a slab of brown sugar ham. Pork is the third most consumed meat in the US, with a buzzing industry to meet demand.

But for over three decades, pig farmers have been plagued by a pesky virus that causes porcine reproductive and respiratory syndrome (PRRS). Also known as blue ear—for its most notable symptom—the virus spreads through the air like SARS-CoV-2, the bug behind Covid-19.

Infected young pigs spike a high fever with persistent coughing and are unable to gain weight. In pregnant sows, the virus often causes miscarriage or the birth of dead or stunted piglets.

According to one estimate, blue ear costs pork producers in North America more than $600 million annually. While a vaccine is available, it's not always effective at stopping viral spread.

What if pigs couldn't be infected in the first place? .

This month, a team at Genus, a British biotechnology company focused on animal genetics, introduced a new generation of CRISPR-edited pigs completely resistant to the PRRS virus. In early embryos, the team destroyed a protein the virus exploits to attack cells. The edited piglets were completely immune to the virus, even when housed with infected peers.

Here's the kicker. Rather than using lab-bred pigs, the team edited four genetically diverse lines of commercial pigs bred for consumption. This isn't just a lab experiment. "It's actually doing it in the real world," Dr. Rodolphe Barrangou at North Carolina State University, who was not involved in the work, told Science.

With PRRS virus being a massive headache, there's high incentive for farmers to breed virus-resistant pigs at a commercial scale. Dr. Raymond Rowland at the University of Illinois, who helped establish the first PRRS-resistant pigs in the lab, said gene editing is a way "to create a more perfect life" for animals and farmers—and ultimately, to benefit consumers too.

"The pig never gets the virus. You don't need vaccines; you don't need a diagnostic test. It takes everything off the table," he told MIT Technology Review.

Genus is seeking approval for widespread distribution from the US Food and Drug Administration (FDA), which it hopes will come by the end of the year.

An Achilles Heel .

The push towards marketable CRISPR pork builds on pioneering results from almost a decade ago.

The PRRS virus silently emerged in the late 1980s, and its impact was almost immediate. Like Covid-19, the virus was completely new to science and pigs, resulting in massive die-offs and birth defects. Farmers quickly set up protocols to control its spread. These will likely sound familiar: Farmers began disinfecting everything, showering and changing into clean clothes, and quarantining any potentially infected pigs.

But the virus still slipped through these preventative measures and spread like wildfire. The only solution was to cull infected animals, costing their keepers profit and heartache. Scientists eventually developed multiple vaccines and drugs to control the virus, but these are costly and burdensome and none are completely effective.

In 2016, Dr. Randall Prather at the University of Missouri asked: "Can't we just create pigs that don't have the blue ear receptor that, when they're infected, they don't get sick?" Prather .