Congenital Tuberculosis in a Stillborn Calf

Bovine tuberculosis is a zoonotic infectious disease of cattle caused by the bacterium <i>Mycobacterium bovis</i>. In adult cattle, transmission is mainly via the respiratory route, whereas, in young calves, oral infection is also common. Congenital tuberculosis is rare. The purpose of this study was to describe in utero infection of a bovine stillbirth. The fetus was necropsied and tissue samples were processed for histopathology, bacteriology and PCR; a sample of the isolated strain was genotyped using spoligotyping. The whole herd was tuberculin skin tested and the dam's serum was also assessed for the presence of antibodies against bovine tuberculosis with indirect ELISA. The macroscopic findings in different organs were consistent with tuberculosis. The histopathology demonstrated typical granulomatous lesions in the liver, spleen, hepatic and mediastinal lymph nodes. Acid-fast bacilli were observed in the smears stained using the Ziehl-Neelsen method. The colonies isolated were PCR-positive for IS6110 and the spoligotype corresponded to SB0140. The dam of the stillborn was positive for indirect ELISA and reacted to a single caudal skin test with bovine tuberculin. The fetal infection in utero with <i>Mycobacterium bovis</i> was confirmed through necropsy, histopathology and bacteriology, reinforcing the importance of testing young animals.