Francisella tularensis


  • Causes tularaemia in wildlife, domestic animals and humans
  • Wildlife reservoir of infection, including rabbits, rodents, galliform birds and deer
  • Survives in the soil for up to 4 months
  • Type A strains associated with terrestrial animal reservoirs; type B strains with water-borne infections and aquatic animals
  • Ticks and deerfly act as vectors
  • Fatal infection in humans, with ulers and lymphadenopathy; vaccine available


  • Gram negative rod with coccobacillary appearance
  • Non-moltile, obligate aerobe
  • Oxidase negative, weakly catalase positive
  • Fastidious, requiring cysteine for growth on blood agar
  • No growth on MacConkey
  • Facultative intracellular pathogen

Pathogenesis and pathogenicity

  • High lipid content; virulent isolates produce capsules
  • Highly virulent type A stains, F. tularensis subspecies tularensis in North America; less virulent type B strains, F. tularensis subspecies holarctica in Eurasia and North America
  • Infection through skin abrasions or arthropod bites, inhalation or ingestion
  • Organism survives and replicates in acidic environment of macrophages by inhibiting phagosome/lysosome fusion
  • Acidic environment required for release of iron, required for growth, from tranferin
  • Lymphadenitis and septicaemia
  • Enlarged lymph nodes with pale necrotic foci
  • Miliary lesions in spleen and liver
  • Pulmonary consolidation; primary pulmonary lesions due to aerosol inhalation in dogs

Clinical infections

  • Fulminant disease in immunosuppressed
  • Septicaemia with fever, depression, inappetence, stiffness
  • Chronic granulomatous or subclinical infections
  • Type A strains cause most infections in domestic animals; type B strains cause mild disease
  • Rare outbreaks of tularaemia in sheep, horses and young pigs
  • Adult pigs and cattle resistant
  • Dogs and cats seroconvert without clinical signs


  • Heavy tick infestation in severely infected animals in an endemic area indicate tularaemia
  • Blood serology - high agglutinating antibody titres or rising antibody titre
  • Scraping from ulcers, lymph node aspirates and biopsy material
  • Post mortem
  • Fluorescent antibody technique on tissues, exudates or culture
  • Glucose-cysteine-blood agar used for culture
  • Small, grey, mucoid colonies, surrounded by narrow zone of incomplete haemolysis, after 3-4 days incubation
  • Immunofluorescence confirms presence in smears
  • Slide agglutination test on cultures
  • Biochemical tests to distinguish type A from type B strains
  • PCR for detection in blood
  • Isolation in embryonated eggs or lab animals


  • Antibiotics including amikacin, streptomycin, fluoroquinolones


  • Ectoparasite control
  • Daily removal of ticks from dogs and cats
  • Prevent dogs and cats hunting wildlife