Role of maternal immunity to PCV2 and PRRSV co-infection in the pathogenesis of PMWS

摘要

Postweaning Multisystemic Wasting Syndrome (PMWS) is a recently emerged disease of nursery and grower pigs. Typically, 5-15 percent of the pigs in a group are affected, and most affected pigs are either culled or die from secondary bacterial infections. Pigs with PMWS have progressive weight loss, labored breathing, and lymph node enlargement. Microscopic examination of tissues from these pigs reveals depletion of lymphoid tissues (tonsil, lymph nodes, spleen) as well as infiltrates of white blood cells in lymph nodes, lung, liver, and kidney. A newly discovered virus, type 2 porcine circovirus (PCV2), is consistently present in tissues from pigs with PMWS. Diagnosis of PMWS is based on demonstration of the characteristic microscopic changes and the presence of PCV2 in the affected tissues. In approximately 60 percent of the PMWS/PCV2 infection cases examined at the ISU-Veterinary Diagnostic Laboratory (VDL), PRRSV co-infection can be demonstrated.