BOVINE PNEUMONIC PASTEURELLOSIS - PART I - PATHOPHYSIOLOGY

Bovine pneumonic pasteurellosis poses a persistent challenge to the ve terinary profession. The causative organisms (Pasteurella haemolytica and P. multocida) can be found among the oropharyngeal flora of health y cattle. The Pasteurella organisms may proliferate and cause clinical disease when the cattle have undergone stress (e,g., as a result of w eaning, dehorning, viral infection, or transport). The disease consist s of lobular consolidation in the cranioventral lung lobes with areas of hepatization. This article, which is Part I of a two-part presentat ion, discusses how the bacteria proliferate and lead to clinical disea se in stressed cattle. Stress responses (e.g.,altered autonomic nerve activity and high levels of circulating catecholamines) may depress pu lmonary and immune function, When stress, physical factors, or viral i nfection disrupt the defenses of the respiratory mucosa, pathogenic ba cteria may proliferate and travel farther down the airways, Part II wi ll discuss the prevention and treatment of bovine pneumonic pasteurell osis and provide further information on the pathophysiology of the dis ease.