PULMONARY-LESIONS INDUCED BY PASTEURELLA-HEMOLYTICA IN CATTLE

Abstract

Twelve 4 mo. old calves were inoculated intratracheally with a large dose of P. haemolytica and the lungs were examined 18 h, 3 days and 7 days later. The gross and microscopic lesions were graded in each calf. The most extensive gross lesions were present at 3 days and were characteristic of a fibrinous pneumonia. Discrete areas of coagulation necrosis were present at 3 days and granulation tissue formed around these by 7 days. Characteristic swirly dark cells accumulated in alveoli and alveolar ducts and were observed from 3 days onwards. The gross and microscopic lesions were similar to those seen in field cases of pneumonic pasteurellosis.