Haemophilus species

BACK TO INFECTIOUS AGENTS AND PARASITES BACK TO BACTERIA

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

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

• H. pleuropneumonia in Contagious porcine pleuropneumonia

Haemophilus paragalinarum

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

Haemophilus influenzae

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