Pneumonic Pasteurellosis in Cattle
Description MANNHEIMIA HAEMOLYTICA and PASTEURELLA MULTOCIDA are the most common bacteria found in bovine pneumonia; probably can be primary pathogens with other agents such as viruses increasing risk for disease. Pneumonia often follows stress such as shipment (shipping fever) and is common in young calves.
Clinical signs of bacterial pneumonia are often preceded by signs of viral infection of the respiratory tract. With the onset of bacterial pneumonia, clinical signs increase in severity and are characterized by depression and toxemia. Fever (104-106°F [40-41°C]); serous to mucopurulent nasal discharge; moist cough; and a rapid, shallow respiratory rate may be noted. Auscultation of the cranioventral lung field reveals increased bronchial sounds, crackles, and wheezes. In severe cases, pleurisy may develop, characterized by an irregular breathing pattern and grunting on expiration. The animal will become unthrifty in appearance if the pneumonia becomes chronic, which is usually associated with the formation of pulmonary abscesses.
Generally, neither serologic testing nor direct bacterial detection are performed, and diagnosis relies on bacterial culture. Because the bacteria involved are normal inhabitants of the upper respiratory tract, the specificity of culture can be increased by collecting antemortem specimens from the lower respiratory tract by tracheal swab, transtracheal wash, or bronchoalveolar lavage. Lung specimens can be collected for culture at postmortem. If possible, specimens for culture should be collected from animals that have not been treated with antibiotics to permit determination of antimicrobial sensitivity patterns.