Comparative pathology of piglets naturally infected with high-pathogenic PRRSV and artificially infected with American strains PRRSV (VR-2332).

In order to find the different pathogenic traits of high-pathogenic PRRSV prevailing in China and American strain PRRSV(VR-2332),the pathological characters and pathogenesis of piglets naturally infected with high-pathogenic PRRSV and artificially infected by American strain(VR-2332) were studied.The results indicated that the typical pathological changes of piglets naturally infected with high-pathogenic PRRSV included quick cyanosis of tips of feet and ears,flecked bleeding in skin,acute consolidation of lung,bleeding necrotic lymphadenitis,acute splenitis,hemorrhagic infarct in the border of spleen,flecked bleeding in kidney as well as gastrointestinal mucous membrane hemorrhage and ulcerations.Dead pigs showed typical changes of acute hemorrhagic septicemia.Acute necrosis of lymphoid tissues,acute viral encephalitis,degeneration and necrosis of parenchymal organs were common tissue pathological change in natural cases.which are main reasons for the death of pigs and secondary infection.The distribution and the appearance of the two kinds of virus particle under electron microscope were the same in lung and spleen as well as positive cells detected by immunohistochemistry in lung,and tonsil.