This study focused on intestinal restitution including phenotype switching of absorptive enterocytes and the abundance of different enterocyte subtypes in weaned pigs after porcine epidemic diarrhea virus (PEDV) infection. At 10 days post-PEDV-inoculation, the ratio of villus height to crypt depth in both jejunum and ileum had restored, and the PEDV antigen was not detectable. However, enterocytes at the villus tips revealed epithelial-mesenchymal transition (EMT) in the jejunum in which E-cadherin expression decreased while expression of N-cadherin, vimentin, and Snail increased. Additionally, there was reduced expression of actin in microvilli and Zonula occludens-1 (ZO-1) in tight junctions. Moreover, the protein concentration of transforming growth factor β1 (TGFβ1), which mediates EMT and cytoskeleton alteration, was increased. We also found a decreased number of Peyer's patch M cells in the ileum. These results reveal incomplete restitution of enterocytes in the jejunum and potentially impaired immune surveillance in the ileum after PEDV infection.

Bovine coronavirus (BCoV) is a known cause of enteric disease in cattle; however, its role in bovine respiratory disease (BRD) is poorly understood, with a dearth of evidence of the detection of the virus in respiratory tract lesions. We coupled histologic evaluation of tracheal and lower airway tissues from 104 calves with BRD in which BCoV was detected in the lungs via PCR followed by direct detection of BCoV by immunohistochemistry and an RNA in situ hybridization assay (ISH; RNAscope technology). RNAscope ISH detected BCoV in respiratory epithelium in more cases than did IHC. Using both methods of direct detection, tracheal epithelial attenuation and identification of the virus within lesions were observed commonly. Our results confirm a role of BCoV in respiratory tract infection and pathology, and show that the virus likely plays a role in the development of BRD.

Nodaviruses are small bisegmented RNA viruses belonging to the family Nodaviridae. Nodaviruses have been identified in different hosts, including insects, fishes, shrimps, prawns, dogs, and bats. A novel porcine nodavirus was first identified in the United States by applying next-generation sequencing on brain tissues of pigs with neurological signs, including uncontrollable shaking. RNA1 of the porcine nodavirus had the highest nucleotide identity (51.1%) to the Flock House virus, whereas its RNA2 shared the highest nucleotide identity (48%) with the RNA2 segment of caninovirus (Canine nodavirus). Genetic characterization classified porcine nodavirus as a new species under the genus Alphanodavirus. Further studies are needed to understand the pathogenicity and clinical impacts of this virus.

Astroviruses infect mammals and birds resulting in either gastroenteritis, neurologic disease, or asymptomatic infection. Porcine astrovirus 4 (PoAstV4) has previously been detected in the upper respiratory tract of pigs with clinical respiratory disease; however, proof of respiratory tract infection and association of the virus with respiratory pathology have not been shown. In this retrospective study of young pigs with clinical respiratory disease of unknown etiology, PoAstV4 was detected with RNA in situ hybridization in lesions consistent with epitheliotropic viral infection in 85 of 117 pigs. This is the first report associating an astrovirus with respiratory pathology.