Pathological features and proposed diagnostic criteria of porcine periweaning failure-to-thrive syndrome.

Porcine periweaning failure-to-thrive syndrome (PFTS) is a clinical syndrome characterized by anorexia and progressive debilitation of newly weaned pigs. The objectives of the current case-control study were to describe the histopathologic features of PFTS in North America and test for selected pathogens in case and control pigs on 8 farms allegedly fulfilling the clinical definition of PFTS. Based on observations during farm visits, 5 farms fully met the case definition (PFTS farms), whereas 3 farms only partially fulfilled the definition (NON-PFTS farms). Necropsy and histopathologic examination were performed on case (n = 8 or 9) and control (n = 4) pigs from each farm. Superficial gastritis, which was mainly localized in the fundus and characterized by attenuation of superficial foveolar cells, was significantly more frequent in case pigs from PFTS farms compared with all the other pigs (odds ratio [OR], 16.7). The same was found for thymic atrophy (OR, 30.1) and small intestinal (SI) villous atrophy in the duodenum (OR, 28.7), jejunum (OR, 67.4), and ileum (OR, 56.3). All pigs with PFTS had at least 2 of these 3 lesions: gastritis, thymic atrophy, and SI villous atrophy. PFTS was not associated with any relevant porcine pathogen tested. We propose the diagnosis of PFTS be based on the fulfillment of the clinical case definition, the presence of the above lesions, and exclusion of other common swine diseases and pathogens. However, PFTS can be ruled out if debilitated pigs do not have at least 2 of the above 3 lesions.