Origin, Evolution, and Virulence of Porcine Deltacoronaviruses in the United States

Ma, Yuanmei; Zhang, Yu; Liang, Xueya; Lou, Fangfei; Oglesbee, Michael; Krakowka, Steven; Li, Jianrong

By 48 h p.i., villous atrophy of the small intestine was further advanced; all divisions of small intestine contained only short blunted villi variably lined by flattened squamoid-to-cuboidal epithelial cells; goblet cells appeared unaffected by the direct viral cytopathic effect and rather were aggregated onto villus tips or sloughed into the intestinal lumen. Many mucosal epithelial cells were necrotic and lysed; nuclear changes consistent with cell death included pyknosis, karyorrhexis, and karyolysis (Fig. 3G ). Epithelium-origin syncytial giant cells were still evident but were fewer in number. In the stomach (Fig. 3E ), occasional dilated gastric pits were observed, presumably created as individual PdCVinfected cells lysed and were replaced by attenuated, immature squamoid epithelial cells. The underlying lamina propria was edematous and contained activated macrophages, occasional aggregates of lymphocytes, neutrophils, and a scattering of eosinophils. These modest inflammatory cell infiltrates were attributable to PdCV, as inflammatory cell infiltrates are notably absent in uninfected Gn swine. Peyer's patches of the ileum and mesenteric lymph nodes were moderately depleted of lymphocytes, as were mesenteric lymph nodes. As is typical of Gn swine, lymphoid follicles (i.e., sites of B-cell differentiation) were either not present or present only as inactive aggregates of lymphocytes.