Detection of Porcine Teschovirus in Tissues of Experimentally Infected Pigs
Date Issued
2009
Date
2009
Author(s)
Lin, Yi-Chien
Abstract
The porcine teschovirus (PTV) belongs to genus Teschovirus of the Picornaviridae family. It was classified as Enterovirus genus before genotyping and reclassified it into 11 serotypes. The virulent PTV-1 strain is associated with Teschen disease, which is a polioencephalomyelitis with high mortality first occurred in Czechoslovakia in year 1929. After year 1957, the lower virulent strain and milder forms of polioencephalomyelitis had occurred in the Talfan district of England, and thus named Talfan disease. The lower virulent strains have since spread all over the world. In Taiwan, the 1st report was at Nantou district in September of year 2000, and had since been reported from Miaoli, Chiayi, and Taichung districts. The purpose of this study was to detect the presence of PTV-1 antigen in tissues, by immunohistochemistry (IHC), of pigs inoculated intranasally with a PTV-1 Taiwan isolate to correlate clinical signs and lesions and to further the understanding of pathogenesis. The observed clinical signs were mainly diarrhea at days postinfection (DPI) 2-5, and cough appeared at DPI 4, and 2 out of 14 pigs presented variably degrees of hind leg paralysis at DPI 4 and 5 respectively. Histologically, all experimental pigs presented mild to moderate interstitial pneumonia, and 6 out of 11 pigs presented perivascular mononuclear cuffing with myelin edema in white matter of cord, and neuronal degeneration in dorsal root ganglion. By IHC, PTV-1 signals were present in tonsil, lamina propia of jejunum, ileum, colon, mesenteric lymph node, lung and spleen, and those have nervous signs were in lumbar, cervical, sacral, and thoracic cords. Based on cellular morphology and a similar PTV-1 signal distribution with leukocyte marker distribution, infected cells were most likely T lymphocyte and macrophages in most organs. Infected cells in the spinal cord were mainly endothelial cells and astrocytes, and minorly T lymphocytes. Based on these findings a hematogenous route of invasion to CNS was most possible, however, a possibility of retrograde axonal transport from the intestines also likely existed. A model of pathogenesis was proposed, wherein lamina propia of intestines and marginal zone and red pulp of spleen play critical roles in sustaining viremia and fecal shedding to facilitate recirculation of the virus within the herd. The neurotropism to certain parts of the CNS remained unclear.
Subjects
porcine teschovirus
immunohistochemistry
experimental animal
spinal cord
tonsil
spleen
SDGs
Type
thesis
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