|Ramirez-Romero, Rafael - FMZ UANL,MONTERREY, MEX.|
Submitted to: Revista Latino Americana de Microbiologa
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 1995
Publication Date: N/A
Interpretive Summary: Pneumonia is a major economic problem of the cattle industry in North America. Affected cattle often have severe lung damage and their lung tissues can contain large numbers of bacteria. Stress placed on the cattle (i.e. rounding up of cattle at the farms, restraint, vaccination, castration, loading and transporting of cattle hundreds of miles to feedlots, unloading, and mixing cattle in high numbers in confined spaces, exposure to organisms from other sources, etc.) prepares them for infection. The disease starts with a massive overgrowth of bacteria in the nasal mucous. Infected mucous is then inhaled into the lung. Bacteria in this mucus produce toxins that damage tissue. Pneumonia then results and some animals die. Despite a large number of studies conducted to explore this complex interaction, there still remains a lack of detailed understanding. This review discusses the role of these tissue damaging factors in the development of lung damage.
Technical Abstract: Pneumonic pasteurellosis is the major economic problem of the cattle industry in North America. This disease is characterized by an acute, severe, fibrinonecrotic pleuropneumonia. Pasteurella haemolytica A1 is commonly isolated from these pneumonic lesions. It has been demonstrated that stress or viral infection compromises defense mechanisms of the upper respiratory tract and lung, predisposing to an initial multiplication of bacteria in the nasopharynx and, subsequently, lungs are deluged with large numbers of bacteria. Once multiplication in the alveoli has begun, virulence factors exert their influence to induce an excessive host inflammatory response that results in severe tissue damage. Despite a large number of studies conducted to explore the complex interaction between P. haemolytica and the host response, there still remains a lack of detailed understanding. This review discusses evidence of the role of the main virulence factors of P. haemolytica on the pathogenesis of pulmonary damage.