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

Abstract

<p>Pneumonia is a leading cause of loss to the sheep and cattle industry throughout the world. <em>Mannheimia (Pasteurella) haemolytica</em> is one of the most important respiratory pathogens of domestic ruminants and causes serious outbreaks of acute pneumonia in neonatal, weaned and growing lambs, calves, and goats.<em>M. haemolytica</em> is also an important cause of pneumonia in adult animals. Transportation, viral infections with agents such as infectious bovine rhinotracheitis virus, parainfluenza-3 virus or bovine respiratory syncytial virus, overcrowding, housing of neonates and weaned animals together and other stressful conditions predispose animals to <em>M. haemolytica</em> infection. This review assimilates some of the findings key to cellular and molecular responses of the lung from a pathologist′s perspective. It includes some of what is known and underscores areas that are not fully understood.</p>