Response of the ruminant respiratory tract to Mannheimia (Pasteurella) haemolytica

Pneumonia is a leading cause of loss to the sheep and cattle industry throu ghout the world, Mannnheimia (Pertelrrella) haemolytica is one of the most important respiratory pathogens of domestic ruminants and causes serious ou tbreaks of acute pneumonia in neonatal, weaned and growing lambs, calves, a nd goats. M. haemolytica is also an important cause of pneumonia in adult a nimals. Transportation, viral infections with agents such as infectious bov ine rhinotracheitis virus, parainfluenza-3 virus or bovine respiratory sync ytial virus, overcrowding, housing of neonates and weaned animals together and other stressful conditions predispose animals to M. haemolytica infecti on [1, 2]. This review assimilates some of the findings key to cellular and molecular responses of the lung from a pathologist's perspective. It inclu des some of what is known and underscores areas that are not fully understo od. (C) 2000 Editions scientifiques et medicales Elsevier SAS.