Pathological and clinical investigations of an outbreak of Blackleg disease due to C. chauvoei in cattle in Punjab, Pakistan

Introduction: Clostridium chauvoei (C. chauvoei) is an anaerobic, histotoxic Gram-positive, bacterium causing fatal myonecrosis in livestock with high mortalities. The disease is common in dairy animals, but little is known about the pathophysiology of the disease in exotic (non-native) animals kept under local conditions in Pakistan. Methodology: Diagnosis of blackleg was made based on hematological and serum biochemical analysis, PCR, necropsy and histopathology. Results: Clinically sick animals exhibited fever, lameness, subcutaneous gaseous swelling and edema particularly in hindquarter and front legs. Hematological analysis showed increases in erythrocyte sedimentation rate and reduces in number of red blood cells, packed cell volume, leukocytes and differential leukocyte count. Serum aspartate aminotransferase, lactate dehydrogenase, alkaline phosphates, alanine aminotransferase, urea, creatinine, creatine kinase, and creatinine phosphokinase were significantly (P < 0.05) higher in the infected animals. At necropsy, swelling areas contained straw-colored fluid with gas bubbles. The muscles were swollen, dark to black and exhibited crepitation sounds at the time of incisions with a rancid odor. Severe pulmonary edema, myocarditis along with petechial hemorrhages, as well as enlargement and congestion of liver and spleen have been observed. Microscopic examination revealed severe inflammatory reaction, edema, and disruption of the myofibrils. Examination of heart, spleen, liver, kidneys, intestine, and lungs showed congestion, severe inflammatory changes with neutrophilic infiltration and necrosis accompanied by dissociation of the normal tissue structure. PCR confirmed C. chauvoei in exudates and different samples of muscles. Conclusion: The pathophysiology should be considered in diagnosis of blackleg. The disease is exist in the non-native cattle farms and biosecurity measures have to be elevated.