Blackleg in a herd of Steer- Clostridium chauvoei


History: A steer was found dead with no prior clinical signs. The farm had 12 animals die (of 550) over the past 10 days.

Gross Findings:

Subcutaneous and muscular emphysema throughout the animal. There was moderate to severe retroperitoneal and mediastinal edema. The hind-limb skeletal muscles had multiple dark red areas and were emphysematous. They had a prominent odor of rancid butter.

Muscle necrosis

Muscle necrosis and hemorrhage

Necrosis and Hemorrhage

Necrosis and Hemorrhage

emphysema, necrosis and hemorrhage

emphysema, necrosis and hemorrhage

Myocardial necrosis and hemorrhage

Myocardial necrosis and hemorrhage

The trachea and main-stem bronchi were filled with a blood-tinged foam. The tracheal mucosa was dark red. The pericardium was filled with approximately 0.5 L of red fluid, and the
epicardial surface was covered with a large amount of fibrin. The ventricular myocardium and the interventricular septa had multiple dark red areas (approximately 4cm x 3cm x 2 cm).
The lungs were diffusely wet and heavy and were adhered by fibrin to the thoracic wall.
The serosal surface of the rumen was multifocally covered with fibrin.

Histopathology:

1. Necrotizing emphysematous myositis and myocarditis, multifocal, severe, with intralesional bacteria.
2. Fibrinous epicarditis

Skeletal muscle: The majority of myocytes are diffusely devoid of nuclei but retain their cross-striations. There are multifocal hemorrhages within the muscle, and scattered foci of edema. Some sections have large clear spaces between myofibers (emphysema), and other sections have small numbers of degenerate neutrophils. There are rare nuclei present.

Necrosis, and emphysema

Necrosis, and emphysema

Necrosis, loss of nuclei and presence of bacteria

Necrosis, loss of nuclei and presence of bacteria

Gram Positive bacilli in skeletal muscle

Gram Positive bacilli in skeletal muscle

Heart: The myocardium is mostly devoid of nuclei, except for several cardiac myocytes. There are multifocal hemorrhages in the myocardium and scattered neutrophils present. There are few rod shaped bacteria
seen. On the epicardial surface is a large aggregation of neutrophils and fibrin.

Diagnosis: A fluorescent antibody test performed on a smear of skeletal muscle was
positive for Clostridium chauvoei. The gross and histological lesions confirm this diagnosis.

Comment: These cattle were not vaccinated for Clostridium chauvoei. The spores are still viable in the soil and cattle can still become infected if not vaccinated.

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About Brian

Anatomic Pathologist, VetPath Services, Stone Ridge, NY- musculoskeletal, oral/dental, and sinonasal diseases
This entry was posted in Necropsy Cases and tagged , , , . Bookmark the permalink.

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