A Japanese Black calf became dehydrated on the first day of life and died on the third day. Gross examination revealed a large amount of yellowish-brown serous fluid in the abdominal cavity and whitish-yellow fibrin in the serosa of the abdominal organs. Patchy red spots were observed throughout the peritoneum, and the outer membrane of the umbilical arteries was dark red. Bacteriologically, Mannheimia haemolytica serotype 2 was isolated from the umbilical arteries and vein, liver, and kidney. Histopathology revealed inflammation with M. haemolytica serotype 2 in the outer membrane of the umbilical arteries and in the serosa of the bladder and intestinal tract. This is the first case of bovine peritonitis with histopathologic and immunohistochemical identification of M. haemolytica.

A 7-month-old Duroc boar exhibited anorexia and dark-bloody diarrhea. Despite antimicrobial therapy including enrofloxacin (fluoroquinolones) and tylosin (macrolides), the boar died. Gross examination showed hepatic abscesses. Histological examination showed chronic multifocal necrotizing and suppurative hepatitis with colonies of Gram-positive cocci. Necrosis was observed in the center of affected areas. The lesions were composed of numerous neutrophils, macrophages, a few lymphocytes, and fibroblasts. Dense fibrous connective tissue surrounded these necrotizing and suppurative lesions. Several cocci were also detected in the multifocal necrotic foci in the liver. The bacteria isolated from the hepatic abscesses were confirmed to be Streptococcus suis serotype 4 based on the results of 16S rRNA gene sequencing and agglutination tests with antisera. Immunohistochemically, the cocci observed in the hematoxylin and eosin and Gram-stained sections of the liver abscess were strongly positive for S. suis serotype 4. Antimicrobial susceptibility testing showed that the isolate was resistant to third generation cephalosporins. Thus, a diagnosis of unique streptococcosis caused by S. suis serotype 4 was made. The typical clinical manifestation of S. suis infection involves meninges, endocardium, joints, and the lungs. The present boar is the first natural case of porcine liver abscess caused by S. suis serotype 4.

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