Leptospirosis outbreak in calves maintained in a rice stubble field

ABSTRACT:

Leptospirosis is an infectious disease caused by bacteria of the genus Leptospira, which affect domestic and wild animals, and also humans. From October to November 2014, in a rural property located in Glorinha, RS, where cattle were kept in the rice stubble, thirteen calves presented hemoglobinuria and apathy, nine of which died within less than 24 hours after the onset of clinical signs. Four calves were necropsied (A, B, C and D). Tissue samples were collected in 10% formalin. Samples of kidney, liver and lung from calves B, C and D were sent for PCR analysis for 16S ribosomal RNA and the protein Lip 32 genes of Leptospira. At macroscopic examination jaundiced mucosae and subcutaneous tissue, orange liver, and lungs with multiple petechiae, predominantly in cranial lobes, were observed. The thoracic cavity of calf A was filled with a reddish fluid. At microscopic examination, severe hemorrhage was observed in the lungs; in the liver there was moderate diffuse centrilobular hepatocellular necrosis and vacuolization, in addition to discrete periportal lymphocytic infiltrate. Discrete multifocal lymphoplasmocytic interstitial nephritis was observed in the kidneys. PCR analyzis resulted positive for calves B and D. The diagnosis of leptospirosis in the calves was based on epidemiological, clinical and pathological findings associated with positive PCR analysis. This study demonstrates the importance of investigation of the disease when young bovids are raised in flooded areas and have clinical signs of an acute septicemic disease.

INDEX TERMS:
Acute leptospirosis; Leptospira sp.; calves; ruminants; septicemic disease