What’s Causing the Increase in Severe Lung Lesion Patterns in Pigs?

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.”