Studies On The Distribution Of Virus Antigen And The Clinical And Pathological Changes In Piglets Infected With PRRSV

The distribution of antigen and clinical and pathological changes were studies in 10-15-day-old piglets of PRRSV free inoculated intranasally with porcine reproductive and respiratory syndrome virus (PRRSV) SJ strain. The interaction of distribution of virus antigen and the light microscopic lesions were evaluated in this paper. The results are as follows.1. PRRSV antigen was found in lung, lymph node, tonsil, nasal mucosa. spleen, kidney in the test group by indirect immunohistochemical staining method at twenty-four hours postinoculation (HPI) up to twenty-eight days postinoculation (DPI) The most intense and widespread PRRSV positive cells in bronchpulmonary lymph nodes and tonsil were at twenty-four hours postinoculation (HPI) up to seven days postinoculation (DPI). The same result in spleen was at fourteen days postinoculation (HPI) up to twenty-eight days postinoculation (DPI). The nucleic acid for PRRSV was seen in spleen and tonsil by RT-PCR The results indicate PRRSV can be persisted for long time in these organs from twenty-four HPI up to twenty-eight DPI and the piglets that infected naturally with PRRSV are most important and infectious resource.The theoretical basis for PRRS prevention is also provided from the results2 The clinical signs changes of piglets infected with PRRSV included mild fever(pyrexia), periocular edema, nasal discharge, dyspnea, lethargy. Gross lesions changes were seen in lungs and lymph nodes. The histological lesions of PRRSV-infected piglets were characterized by infiltration of macrophages and lymphocytes in alveolar septum, peribronchial lymphoid hyperplasia in the peri bronchial area and interstitial pneumonia. The lesions were severe at prolong postinfection period. There was no correlation between the histological lesions of the tissues and reactive degree and amount of PRRSV positive cells in tissues. Ultrastructurally, abnormal morphological nucleus and disappeared nucleopore were found in the hyperplastic monocytes in the alveolar septum. The type II alveolar cells were severe degeneration and the membrane of rough endoplasmic reticulum was broken.