- 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
- Contagious Footrot
- Necrobacillosis
- Laryngeal Chondritis