Necrotizing hepatitis caused by Clostridium novyi type B in a dog with no predisposing liver lesions: a case report

Abstract

Background: Infectious necrotic hepatitis (INH) is typically a disease of ruminants caused by Clostridium novyi type B. Growth of the causative agent is supported by development of an anaerobic environment within the liver. In dogs, C. novyi is rare and has only been previously reported as a post-mortem diagnosis. In one case, infection was secondary to metastatic pancreatic adenocarcinoma and the other was presumptively diagnosed on histopathology of a hepatic lesion in a dog initially presented for acute collapse.

Case presentation: An 8-year-old spayed, female mixed breed dog was presented for acute onset of hyporexia and vomiting. Serum biochemistry revealed elevated hepatocellular injury and cholestatic liver enzymes. Ultrasound revealed peritoneal fluid accumulation and multiple hepatic masses. Cytologic examination of liver aspirates and peritoneal fluid revealed frequent 4 × 1 μm bacilli with a terminal endospore. Anaerobic bacterial growth isolated from the fluid sample could not be identified using typical laboratory identification techniques. Long-read, whole genome sequencing was performed, and the organism was identified as Clostridium novyi type B. Antimicrobial and hepatic support treatment were initiated. The patient re-presented 27 days later, and the follow up liver aspirate with cytology revealed no appreciable bacteria and anaerobic culture was negative. The patient was presented four months later and a large hepatic mass and peritoneal fluid were again identified on abdominal ultrasound. Cytologic examination of the peritoneal fluid revealed bacilli similar to those identified on initial presentation. The patient was euthanized. The most significant finding on necropsy was necrotizing hepatitis with intralesional endospore-forming bacilli compatible with recurrence of Clostridium novyi type B. There was no identifiable cause of an anaerobic insult to the liver.

Conclusions: This case demonstrates the diagnostic utility of using cytology as part of the initial diagnostic work up for infectious hepatitis. The cytologic findings coupled with whole genome sequencing and anaerobic culture were crucial for the identification and classification of the organism identified on fine needle aspirate. Clostridium novyi type B should be considered when bacilli organisms containing a terminal endospore are identified on liver aspirates collected from canine patients.

Keywords: Canine infectious hepatitis; Case report; Clostridium novyi; Infectious necrotic hepatitis.

Fig. 1

Liver cytology at the time of initial diagnosis (Day 0). There are many vacuolated hepatocytes and moderately increased numbers of degenerate neutrophils admixed with frequent 4 μm × 1 μm bacilli that frequently contain a terminal endospore imparting a “safety pin” morphology (thin arrows). Bacteria are commonly identified within degenerate neutrophils (star) and associated with hepatocytes (thick arrows). Giemsa, 50X magnification

Fig. 2

Timeline of clinical data, diagnostic tests, and antimicrobial therapies for this case

Fig. 3

Post-mortem liver histopathology. The tissue architecture is disrupted by regionally extensive foci of coagulative necrosis with inflammation, abundant fibrin (circled), and Gram-positive bacilli measuring up to 20 μm long × 2 μm wide with a terminal endospore (thin arrows). Regions of necrosis are surrounded by bands of degenerate neutrophils and few foamy macrophages. Hematoxylin and eosin, 20X magnification