A historically rare syndrome in pigs — a severe lung lesion pattern called diffuse alveolar damage (DAD) — is showing up in a growing number of submissions to the Iowa State University Veterinary Diagnostic Laboratory.
DAD is most frequently observed as a syndrome in cattle, referred to as atypical interstitial pneumonia, which is associated with ingested toxins. Unlike cattle, DAD is poorly documented in pigs, with only rare reports of compatible lesions associated with porcine respiratory coronavirus infection and a historical association with porcine circovirus Type 2 (PCV2), the Swine Health Information Center (SHIC) reports.
In pigs with respiratory disease complex, “thumping” is caused by decreased oxygenation and lung compliance. This pattern of interstitial pneumonia occurs as a sequela of systemic insult due to endotoxemia and bacterial or viral infections and is most often associated with porcine reproductive and respiratory syndrome (PRRSV) and PCV2 infections in swine.
What’s Causing the Surge of DAD in Swine?
To understand what may be driving this increase in submissions, SHIC funded a study led by Marcelo Almeida and investigated the etiology of this emergent swine respiratory disease syndrome. A total of 42 DAD cases were reviewed by veterinarians and tested by PCR for common respiratory viruses, including PRRSV, Type A influenza viruses (IAV), and PCV2, and next-generation sequencing to detect other viruses.
Lisa Becton, DVM and associate director of the SHIC, says this is the purpose of SHIC: to provide funding for further diagnostics and research to help identify emerging pathogens and diseases of concern in the U.S. pork industry.
“What leads up to different studies like this is seeing an increase in an unusual clinical presentation,” Becton says. “When we see an increase, that may be a signal of an emerging disease or an emerging syndrome. That’s a trigger to do a deeper dive to determine the underlying cause and ultimately figure out what to do about it.”
The study revealed no single virus consistently explained the DAD lesions. Becton notes that the study suggests controlling PRRSV, IAV, PCV2 and mycoplasma through vaccination and sound herd management remains the best strategy available today to help reduce the risk of this severe lung damage in pigs.
Why Should Producers Take Note?
If you see something unusual or outside of the norm, submit diagnostic samples if you can. Becton says this allows a diagnostic veterinary professional to sort through diagnostic results to help determine what is going on. If they can’t answer that question, it could lead to more in-depth diagnostics.
“Think back to PED,” she says. “We all knew symptoms of TGE before we had the PED outbreak. Everyone said, ‘This is TGE. We will manage it and go on.’ There’s a lot of instances where emerging diseases, and even foreign animal diseases, can be masked as diseases we have seen before.”
Any time you see something that’s not normal, it should be a trigger to ask questions and call your veterinarian, Becton says.
“Is this something we just haven’t seen in a while? Or is this new? What do we need to do to manage it or prevent it from spreading?” she asks. “Whether it’s emerging, or even if it’s a PRRS strain that’s changed, it still makes a difference to investigate it. If we can find it early, then we can take action to reduce potential losses down the road.”
