Immunohistochemical investigation on proliferative and necrotizing pneumonia (PNP) in Italy: preliminary results.

Proliferative and necrotizing pneumonia (PNP) is a particular form of interstitial pneumonia in weaning and post-weaning pigs characterized by hypertrophy and hyperplasia of type II pneumocytes and presence of coagulative necrosis and granular debris within alveolar spaces. American and European studies suggest PRRSV and PCV2 as the probable causes of the disease. An immunohistochemical study was carried out on 24 PNP lungs to evaluate the role of PRRSV and PCV2 in PNP lesions in Italy. Results were as follows: co-infection (PCV2 and PRRSV) in 7 PNP lungs, PRRSV only in 9, PCV2 only in 4, and neither of the two antigens was found in the remaining 4. These findings support the major role of PRRSV as cause of PNP in Italy, even if co-infection is characterized by more severe histological aspects.