Pathogenesis and clinical aspects of a respiratory porcine reproductive and respiratory syndrome virus infection

Some pathogenetic and clinical aspects of the respiratory tract infection with porcine reproductive and respiratory syndrome virus (PRRSV) are discussed. The acute and persistent stages of PRRSV infection are treated separately. Special attention is given to the author's work on experimental dual infections with PRRSV and other enzootic porcine respiratory viruses. It was concluded that: (1) Studies on the interactions of PRRSV and its target cell, the pulmonary alveolar macrophage, are very scarce. So far, the hypothesis of impaired macrophage function has not been proven. (2) The possibility that PRRSV causes disease in growing pigs in combination with other viral or bacterial infections has been demonstrated experimentally. Variation in disease resulting from such combined PRRSV infections will probably hamper future research into disease mechanisms. (3) There remains a need for more data on the clinicopathological significance of the persistent stage of PRRSV infections.