Haemophilus species

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Overview

  • Inhabit mucosal epithelium of upper respiratory and lower genital tract
  • Suppurative infections due to release of pro-inflammatory cytokines released from macrophages
  • Serofibrinous to fibrinopurative infections of lungs, body cavities and joints
  • Colonisation of meningeal vessels causes a thrombotic vasculitis leading to encephalitis and meningitis


Haemophilus characteristics

  • Morphologically variable Gram-negative bacilli, ranging from short rods to long filaments
  • Facultative anaerobes
  • Typically oxidase positive
  • Depend on beta-nicotinamide adenine dinucleotide (NAD) (V factor) and/or Haemin (X fector) for growth
  • Heated blood agar (Chocolate Agar) required for growth of NAD-dependent strains
  • Haemin-dependent strains grow on Blood Agar
  • Do not grow on MacConkey agar


Haemophilus parasuis

  • Inhabits nasopharynx of normal swine
  • Serotype B causes Glasser's disease in pigs
  • Glasser's disease
    • Due to transport, environmental stresses, dietary and managemental factors
    • Acute septicaemia
    • Causes a polyserositis - pericarditis, peritonitis, pleurisy and meningitis - in pigs 3-10 weeks old
    • Also causes suppurative bronchopneumonia, pleuritis, polyarthritis (also H. suis)
    • Expressed lesions vary between animals - meningitis is most consistent, arthritis in 20% of cases
    • Sporadic outbreaks in the UK
    • Can be fatal in 2-5 days
    • Mortality up to 50% insome outbreaks
    • Chronic arthritis, meningitis and intestinal obstruction due to adhesions in surviving pigs
  • Fibrinous pneumonia secondary to enzootic pneumonia or virus infection e.g. swine influenza


Haemophilus somnus

  • Haemophilus sommus in Enzootic pneumonia of calves
  • Causes infectious thromboencephalitis in cattle 1-3 years old
  • Found in the USA and Europe, including UK
  • Causes a meningoencephalitis with fibrinous arterial thrombosis and necrosis
  • Causes fever, staggering and dyspnoea, progressing to somnolence, paralysis and death
  • Mortality can be high


Haemophilus pleuopneumonia


Haemophilus paragalinarum

  • Infectious coryza of poultry
  • Resistant to complement-mediated lysis and phagocytosis


Haemophilus influenzae

  • Human meningitis, septicaemia, bronchopneumonia, conjunctivitis, epiglottitis, and otitis