This study was carried out to study the most common bacterial causes of pneumonia in lambs in certain farms in Zagazig city, Sharkia Province, to evaluate the acute Phase Proteins as inflammatory markers and the most obvious pathological changes in lungs and bronchi. In this study,50 lambs were used, (aged3-6 months),divided into two groups.Gp1(25 healthy lambs) and Gp2 (25Pneumonic lambs).Nasopharyngeal swabs and two blood samples from each lamb were taken for bacteriological examination and biochemical analysis to determine serum total proteins, albumin, C Reactive Proteins (CRP), Haptoglobin (Hp), and Plasma Fibrinogen (PF). Specimens were taken from lungs and bronchi of  lambs in Gp2for histopathological study. The obtained results revealed that E.coli, Staphylococcus aureus and Pasteurella hemolytica are the main common causes of pneumonia in lambs. A significant increase in CRP, Hp and PF levels in pneumonic lambs, also,  an increase in serum total proteins supplemented with a decrease in serum albumin in pneumonic lambs. Lungs of pneumonic lambs showed severe congestion and thrombosis of pulmonary blood vessels. Thickening of interlobular septa, emphysema associated with consolidated areas in addition to suppurative and fibrinous pneumonia were seen.
From this study, it can be concluded that , E.coli, S.aureus and P. hemolytica are the common causes of bacterial pneumonia in certain farms in Zagazig city. The inflammatory markers are indicative of inflammation; lungs were suffering from Fibrinous and Suppurative pneumonia leading to high mortality in lambs in this study.