Experimental Hemorrhagic Septicemia of Calves with Pasteurella multocida Serotype E:2: Clinical, Pathologic and Microbiologic Studies

Abstract

Hemorrhagic septicemia (HS) was experimentally induced in seven-month-old calves (n = 2) by intratracheal inoculation of 10¹⁰ colony-forming units of sixhour log-phase Pasteurella multocida serotype E:2 to study its clinicopathologic features and microbiology. The incubation period was within four hours postinfection. The general continuum of clinical signs in order of manifestation was pyrexia, anorexia, dyspnea, swelling of the throat-forelimb region, tympany, nasal discharge, profuse salivation, lethargy, recumbency and death. The prominent lesions observed at necropsy were congestion of the lungs with consolidation and pleural adhesions of the apical lobes, pleurisy, edematous swelling of the throat and dewlap which exuded yellowish serum-like fluid, petechial and ecchymotic hemorrhages. Histologically, the lung lesions were typical of fibrinous bronchopneumonia with thickened alveolar septa, hyperemia, edema and cellular responses of the lungs. P. multocida E:2 was re-isolated bacteriologically from the lungs, lymph nodes, liver, kidneys, spleen, edema fluid, and heart blood at necropsy. The organism was not detected in the venous blood until a few hours before death. The clinical and pathological features seen in the animals showed that there were striking similarities with P. multocida type B:2 HS. The data should help veterinarians recognize suspected cases of HS in the field.