Experimental hepatic necrobacillosis infection in cattle

Area of Science:

• Veterinary Pathology
• Bacteriology
• Animal Science

Background:

• Fusobacterium necrophorum is a key pathogen causing bovine hepatic necrobacillosis.
• Understanding the early pathogenesis of liver abscesses is crucial for effective treatment and prevention strategies in cattle.

Purpose of the Study:

• To characterize the sequential development of hepatic lesions caused by Fusobacterium necrophorum in cattle.
• To elucidate the host-bacterial interactions during the early stages of experimental hepatic necrobacillosis.

Main Methods:

• Inoculation of viable Fusobacterium necrophorum into the hepatic portal veins of 7 cattle.
• Macroscopic and microscopic examination of liver lesions at time points ranging from 30 minutes to 36 hours post-inoculation.

Main Results:

• Two distinct lesion development patterns were observed: microabscesses initiated by diffuse bacteria (30 min-2 hrs) and emboli-initiated infections.
• Early lesions (3-8 hrs) featured neutrophil infiltration around abscess cores, transitioning to macrophage-dominated infiltrates by 12-36 hrs.
• Hepatocytes adjacent to bacteria showed coagulation necrosis with limited leukocyte presence in some lesion types.

Conclusions:

• Fusobacterium necrophorum rapidly induces hepatic lesions in cattle through distinct host-bacterial interactions.
• The inflammatory response evolves from neutrophilic to macrophagic, indicating a dynamic host defense mechanism.
• The study provides a detailed timeline of experimental hepatic necrobacillosis pathogenesis.