Abstract: The ultra microstructure of lung, spleen, liver,lymph node and other tissues from pigs infected with Shanxi variant strain of PRRSV were observed by transmission electron microscopy (TEm). Results showed that the pulmonary macrophages, the hepatocytes and the lymphocytes in the lymph nodes and the spleen were infected to different degrees, where the membranous structures of organelles was generally damaged, furthermore, the damage of mitochondria and cell nucleus was especially serious. The study shed light on pathogenesis of the disease.

Key words: variant strain of porcine reproductive and respiratory syndrome virus (PRRSV); ultrastructure; swine