Fusobacterium necrophorum

• Characteristics:
  • Normal inhabitant of mammalian gut; cannot invade normal tissue
  • Pleimorphic - long and filamentous or short cocci
  • Fermentative
  • Haemolytic on blood agar
  • Grey, round, shiny colonies
  • Three biotypes: biotype A has greatest haemolytic activity and virulence
• Pathogenesis and pathogenicity:
  • Primary pathogen in various diseases of farm animals
  • Mixed bacterial infections
  • Can be secondary to IBR
  • Extracellular haemolysin contributes to infection
  • Heat-stable leucocidin - correlated with biotype and virulence
  • Cytoplasmic toxin - haemolytic
  • LPS endotoxin causes host damage
  • Antibodiy levels rise with age, suggesting that these are not protective
• Calf diphtheria/necrotic laryngitis in cattle:
  • Necrobacillosis of mouth and pharynx of young calves
  • Pharyngitis and laryngitis
  • Associated with bucket feeding where buckets are contaminated with faeces
  • Bacteria enter through abrasions in the mucosa of the pharynx and larynx
  • Fever, depression, anorexia, salivation, respiratory distress and halitosis
  • Aspiration of necrotic material into lungs may cause fatal bronchopneumonia
  • Treatment: potentiated sulphonamides or tetracyclines
• Bovine liver abscesses:
  • Sudden change in diet to a high grain diet causes ruminal acidosis and rumenitis
  • Ulceration of rumenal mucosa and colonisation by F. necrophorum and Arcanobacter pyogenes
  • Emboli carry organisms to the liver via the portal vein
  • Focal necrosis and abscess formation in liver
  • Putrid smell
  • Rarely show clinical signs
  • Management important
• Necrotic rhinitis of pigs:
  • Sporadic condition in young pigs
  • Suppuration and necrosis of snout
  • F. necrophorum and other organisms enter through abrasions in snout mucosa
  • Facial swelling, sneezing, putri nasal discharge
  • Chronic infection - faical deformity
  • Treat with potentiated sulphonamides
  • Occasional pharyngitis/laryngitis in pigs
• Thrush of the hoof:
  • Necrosis of horse hoof associated with poor hygiene, wet conditions
  • F. necrophorum secondary to hoof damage causes localised inflammatory response
  • Thrush especially of hind feet, with putrid discharge in sulci
  • Provide dry, clean bedding
• Black spot of bovine teats
  • Localised necrosis and scab formation of teat orifice and sphincter of dairy cows due to F. necrophorum
  • May predispose to mastitis
• Necrotic wound infections often in association with facultative anaerobes
• Interdigital dermatitis (pododermatitis) in sheep in association with D. nodosus and Arcanobacter pyogenes, predisposing to footrot
• Causes laryngeal chondritis in sheep
• Mixed infections in heel abscesses in sheep
• Mixed infections in pyothorax
• Mixed infections in aspiration pneumonia and in bovine traumatic reticuloperitonitis and pericarditis
• Involved in subcutaneous abscesses due to cat bites
• May be involved in chronic fibronecrotic rhinitis
• Osteitis