Tularemia

Tularemia is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Tularemia is an acute febrile illness caused by the small aerobic gram-negative pleiomorphic intracellular coccobacillus Francisella tularensis:
    • Organism is highly infectious
    • Person-to-person transmission has not been reported
  • Humans become infected through different environmental exposures:
    • Bites from infected tick, deer fly, mosquito, or other infected insect
    • Direct contact with infectious animal tissue or fluid
    • Contact with or ingestion of contaminated food, water, or soil
    • Inhalation of infected aerosols (e.g., cutting grass with power mowers, which may aerosolize the organism)
    • Prevention should focus on insect repellents, avoiding untreated surface water, using gloves when handling animals such as rabbits, prairie dogs, rodents, and cooking meat thoroughly
  • The 4 major strains of the bacterium have different virulence and geographic location:
    • Two subspecies cause human infection in North America: F. tularensis subspecies tularensis (type A, more virulent) and F. tularensis subspecies holartica (type B, less virulent). In Europe, type B predominates
  • Natural hosts:
    • Lagomorphs and other rodents
    • Found in species of wild animals (rabbits, hares, ticks, muskrats, beavers, mice), domestic animals (sheep, cattle, cats), ticks, and water and soil contaminated by infected animals
  • Natural vectors:
    • Ticks
    • Biting flies
    • Mosquitoes
    • Wild rabbits
    • Rodents
  • Weaponization of tularemia was accomplished during the Cold War:
    • Because of its virulence and ability to be aerosolized, it remains a potential biological agent for mass destruction
  • Laboratory technicians handling culture specimens are at high risk:
    • F. tularensis cultures should be manipulated only in a biosafety level 3 facility

Etiology

  • Individuals who spend time outdoors in endemic areas are at higher risk:
    • Farmers
    • Hunters
    • Forest workers
    • Lawnmowers/landscapers
    • Those who handle animal carcasses are at highest risk (taxidermists and butchers)
    • Those in contact with polluted waters
    • Two-thirds of cases occur in males
  • Although tularemia can occur worldwide, it is endemic in the Northern Hemisphere:
    • Reported nationwide except in Hawaii
    • States with the highest incidence include Missouri, Arkansas, Kansas, South Dakota, and Oklahoma
    • Increased incidence in Colorado, Nebraska, South Dakota, and Wyoming
    • Few hundred cases annually in the U.S., although probably underreported
    • Peak season is June–October
  • Mortality is 5–15%. Appropriately treated patients have mortality as low as 1%.

Pediatric Considerations
  • 25% of cases occur in children 1–14 yr of age
  • Children who spend time outdoors in endemic rural areas are at risk

-- To view the remaining sections of this topic, please or --

Basics

Description

  • Tularemia is an acute febrile illness caused by the small aerobic gram-negative pleiomorphic intracellular coccobacillus Francisella tularensis:
    • Organism is highly infectious
    • Person-to-person transmission has not been reported
  • Humans become infected through different environmental exposures:
    • Bites from infected tick, deer fly, mosquito, or other infected insect
    • Direct contact with infectious animal tissue or fluid
    • Contact with or ingestion of contaminated food, water, or soil
    • Inhalation of infected aerosols (e.g., cutting grass with power mowers, which may aerosolize the organism)
    • Prevention should focus on insect repellents, avoiding untreated surface water, using gloves when handling animals such as rabbits, prairie dogs, rodents, and cooking meat thoroughly
  • The 4 major strains of the bacterium have different virulence and geographic location:
    • Two subspecies cause human infection in North America: F. tularensis subspecies tularensis (type A, more virulent) and F. tularensis subspecies holartica (type B, less virulent). In Europe, type B predominates
  • Natural hosts:
    • Lagomorphs and other rodents
    • Found in species of wild animals (rabbits, hares, ticks, muskrats, beavers, mice), domestic animals (sheep, cattle, cats), ticks, and water and soil contaminated by infected animals
  • Natural vectors:
    • Ticks
    • Biting flies
    • Mosquitoes
    • Wild rabbits
    • Rodents
  • Weaponization of tularemia was accomplished during the Cold War:
    • Because of its virulence and ability to be aerosolized, it remains a potential biological agent for mass destruction
  • Laboratory technicians handling culture specimens are at high risk:
    • F. tularensis cultures should be manipulated only in a biosafety level 3 facility

Etiology

  • Individuals who spend time outdoors in endemic areas are at higher risk:
    • Farmers
    • Hunters
    • Forest workers
    • Lawnmowers/landscapers
    • Those who handle animal carcasses are at highest risk (taxidermists and butchers)
    • Those in contact with polluted waters
    • Two-thirds of cases occur in males
  • Although tularemia can occur worldwide, it is endemic in the Northern Hemisphere:
    • Reported nationwide except in Hawaii
    • States with the highest incidence include Missouri, Arkansas, Kansas, South Dakota, and Oklahoma
    • Increased incidence in Colorado, Nebraska, South Dakota, and Wyoming
    • Few hundred cases annually in the U.S., although probably underreported
    • Peak season is June–October
  • Mortality is 5–15%. Appropriately treated patients have mortality as low as 1%.

Pediatric Considerations
  • 25% of cases occur in children 1–14 yr of age
  • Children who spend time outdoors in endemic rural areas are at risk

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