Difference between revisions of "Francisella tularensis"

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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
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{{review}}
<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
 
  
 
===Overview===
 
===Overview===
  
*Causes tularaemia in animals and humans
+
*Causes tularaemia in wildlife, domestic animals and humans
 
*Wildlife reservoir of infection, including rabbits, rodents, galliform birds and deer
 
*Wildlife reservoir of infection, including rabbits, rodents, galliform birds and deer
 
*Survives in the soil for up to 4 months
 
*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
 
*Type A strains associated with terrestrial animal reservoirs; type B strains with water-borne infections and aquatic animals
 
*Ticks and deerfly act as vectors
 
*Ticks and deerfly act as vectors
 +
*Fatal infection in humans, with ulers and lymphadenopathy; vaccine available
  
  
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*High lipid content; virulent isolates produce capsules
 
*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
 
*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 - Anatomy & Physiology|spleen]] and liver
 +
*Pulmonary consolidation; primary pulmonary lesions due to aerosol inhalation in dogs
  
  
 
===Clinical infections===
 
===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
 +
 
 +
 
 +
===Diagnosis===
 +
 
 +
*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
 +
 
 +
 
 +
===Treatment===
 +
 
 +
*Antibiotics including amikacin, streptomycin, fluoroquinolones
 +
 
 +
 
 +
===Control===
 +
 
 +
*Ectoparasite control
 +
*Daily removal of ticks from dogs and cats
 +
*Prevent dogs and cats hunting wildlife
 +
[[Category:Bacteria miscellaneous]][[Category:Gram_negative_bacteria]][[Category:Coccobacilli]]
 +
[[Category:Rods]]
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[[Category:To_Do_-_Bacteria]]

Latest revision as of 10:23, 25 June 2010


Overview

  • 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


Characteristics

  • 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


Diagnosis

  • 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


Treatment

  • Antibiotics including amikacin, streptomycin, fluoroquinolones


Control

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