What Can PRRS and PEDV Teach Us About COVID-19?

( National Pork Board and the Pork Checkoff )

In 2013, a novel coronavirus called porcine epidemic diarrhea virus (PEDV) reared its ugly head in U.S. swine herds for the first time. The U.S. swine herd had no immunity to this virus strain that was more than 99.5% similar to a Chinese strain. 

“It spread quickly and was incredibly detrimental. There was 80-100% mortality in suckling pigs until immunity was established or the disease was walked out of different herds, resulting in 3.2% loss to the U.S. pig herd - a $900-million to $1.8-billion economic impact,” explains Cassandra Jones, associate professor of in the Department of Animal Sciences and Industry at Kansas State University.

What can we learn from PEDV?
Although both COVID-19 and PEDV are both coronaviruses, Jones says there are key differences between the two. 

PEDV ravages the digestive tract, destroying enterocytes (abosorptive cells in the small intestine). Not only does it limit the ability to absorb nutrients from feed, but it also results in massive diarrhea. PEDV takes the hardest toll on young piglets. It is not a disease that can affect humans. Pork from affected pigs is safe for human consumption.

Meanwhile, COVID-19 impacts human health, resulting in respiratory distress. It primarily includes symptoms of fever, coughing and shortness of breath, Jones adds. 

“I’ve spent most of my academic career at Kansas State University researching ways that PEDV spreads and how to contain it. COVID-19 worries me because, like the U.S. pig population in 2013, there is little-to-no immunity built up to the disease,” Jones says. 

What works to stop or slow down PEDV? Cleaning and disinfection, isolation, thermal treatment and some chemicals, such as medium chain fatty acids/monoglycerides. Jones says implementing human “biosecurity” protocols will help limit spread. 

“Science supports that limiting movements (whether it be people or pigs) reduces disease transmission,” she says.

What can we learn from PRRS?
In a new paper released by the Imperial College of London COVID-19 Response Team, the authors describe two potential approaches to managing disease: Mitigation to slow disease spread (but not necessarily stop it) and suppression to reverse the epidemic threshold and maintain that suppression.

Jones says this is similar to what happens in animal health when a disease becomes endemic. 

“Some production systems choose to live with disease while others are constantly trying to fight its introduction. One great example is porcine reproductive and respiratory syndrome virus (PRRSV). It was first introduced in 1987 but took years to recognize and manage. It still affects the U.S. swine herd,” she says.

Now, 33 years later, swine veterinarians are still arguing which method is best to control disease, she says. Most veterinarians opt for a negative herd, accepting that there may be catastrophic losses from time to time if the virus enters a naive herd, but that the improved mortality and performance during times of high health will lead to greater outcomes on average over time.

“We now face a similar reality, but in human health," Jones says. "Should we try to ‘flatten the curve’ so it spreads inevitably, but more slowly, as to hopefully not overwhelm healthcare systems? Or should we be much more aggressive and try to eliminate this thing altogether?”

Mitigation, or ‘flattening the curve’ will still lead to illness far above surge capacity of hospitals, with a peak epidemic expected in June or December. 

Instead, Jones believes suppression should be the strategy. In the Imperial College of London article, it describes that stopping public gatherings of normal, healthy adults has little impact. Instead, the “most effective combination of interventions is predicted to be a combination of case isolation, home quarantine and social distancing of those most at risk.” 

“Even then, we’re looking at June or July as peak of this thing, and 8X more critical care beds needed than we have available,” Jones says.

At the end of the day, she encourages people to follow good biosecurity and stay calm.

“Panic – economically, socially, politically – only adds to the chaos, and there should be a balance between minimizing disease transfer and how it impacts the rest of our world,” Jones says.

Read more from Farm Journal’s PORK:
5 Ways PRRS Made Us Better

PEDV: Hysteria is Gone, but Disease Isn’t

Lessons Learned From PEDV Could Keep ASF Out of the U.S.

Here's What Makes Coronavirus and African Swine Fever Different