PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME - CLINICAL-DISEASE, PATHOLOGY AND IMMUNOSUPPRESSION

Porcine reproductive and respiratory syndrome (PRRS) was first known a s blue-eared pig disease in the United Kingdom and the causative agent as 'Lelystad virus', The disease is characterised by very variable cl inical signs, including reproductive failure and respiratory disease. The respiratory syndrome is often associated with severe infection wit h secondary bacterial agents including Pasteurella multocida, Haemophi lus parasuis and Streptococcus suis. However, some seropositive herds show no clinical signs of disease, The secondary infections may be fac ilitated by the destruction of circulating lymphocytes, by the destruc tion of the mucociliary clearance system and, most importantly, by a l arge reduction in the numbers of alveolar macrophages. The clinical sy ndrome observed in a herd may therefore depend in part upon the other diseases present.