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Francisella tularensis

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Title: Francisella tularensis


1
Francisella tularensis
  • Tularemia

2
Francisella tularensis
  • Gram stain
  • Poorly staining,
  • tiny Gram-negative
  • coccobacilli

3
Francisella tularensis
  • - One of the most infectious pathogenic bacteria
    known
  • - Inoculation or inhalation of as few as ten
    organisms can cause disease
  • - Extreme infectivity
  • - Substantial capacity to cause illness and
    death
  • Humans cannot transmit infection to others

4
Can Survive For Weeks
  • Water
  • Soil
  • Moist hay
  • Straw
  • Decaying animal carcasses
  • Because it is.
  • Hardy, non-spore forming organism

5
Reservoirs
  • Small and medium sized mammals are the
    principal natural reservoirs for F. tularensis
  • Rabbits
  • Aquatic Rodents (Beavers, Muskrats)
  • Rats
  • Squirrels
  • Lemmings
  • Mice

6
Vectors
  • Ticks
  • Mosquitoes
  • Biting Flies

7
Also Known As
  • Deer-fly fever (Utah)
  • Glandular tick fever (Idaho and Montana)
  • Market mens disease (Washington D.C.)
  • Rabbit fever (Central States)
  • OHaras disease (Japan)

8
History
  • First isolated in 1911 from a plague-like disease
    among ground squirrels in California
  • Its epidemic potential became apparent in the
    1930s and 1940s when large waterborne outbreaks
    occurred in Europe and the Soviet Union and
    epizootic-associated cases occurred in the U.S.

9
Incidence across the Globe
Country Years of Cases
Japan 1924-1987 1,355
Slovakia 1985-1994 126
Turkey 1988-1998 205
10
Modern Worldwide Death Rate
  • Before antibiotics
  • pneumonic tularemia50
  • localized tularemia5
  • After antibiotics
  • 2.3

11
Reported Cases of Tularemia - 1990-1998
12
Four States
  • Four states accounted for 56 of all reported
    tularemia cases
  • Arkansas (23)
  • Missouri (19)
  • South Dakota (7)
  • Oklahoma (7)

13
U.S. Outbreaks
  • Vermont, 1968
  • 47 cases in people who handled muskrats four
    weeks before the onset of the illness
  • No fatalities, but 14 patients had severe
    prostrating illness that lasted an average of ten
    days
  • Utah, 1971
  • 39 cases, most contracted from the bite of an
    infected deerfly
  • All patients recovered

14
U.S. Outbreaks, cont.
  • South Dakota, 1984
  • 20 cases of glandular tularemia in children
  • Illness was mild
  • presumed to be caused by type B
  • Marthas Vineyard, 2000
  • 15 cases of tularemia
  • 11 patients had primary pneumonic disease
  • 1 fatality
  • Caused by type A

15
OUTBREAK!August, 2002Prairie Dogs
  • Health officials were notified that some prairie
    dogs at a Texas pet distribution facility had
    died unexpectedly
  • After officials determined that they had died of
    Tularemia, further investigation found that
    several hundreds of potentially infected dogs
    were shipped to Ohio, West Virginia, Florida,
    Washington, Mississippi, Nevada, Illinois, and
    Virginia

16
It gets even worse, as
  • Shipments also went out to Japan, the Czech
    Republic, the Netherlands, Belgium, Spain, Italy,
    and Thailand

17
Case Incidence
  • The highest incidence of cases was in 1939, when
    2,291 cases were reported
  • The number remained high throughout the 1940s
  • Declined in 1950s to the relatively constant
    number of cases it is nowless than 200 per year
  • Most cases occur in rural environments rarely do
    they occur in urban settings

18
Why the decrease in cases?
  • The development of effective antibiotics
  • Decrease in hunting in the U.S. and other
    developed nations reduced human exposure

19
Fransicella tularensisHistorical Background
  • First described by McCoy in 1912 as agent
    responsible for a tularemia outbreak in Tulare
    County in California and isolated the organism
    from infected squirrels.
  • Francis one of the premier researchers in the
    field elucidated the route of infection in man
    as
  • Rodents?Blood Sucking Insects?Man

20
Fransicella tularensisArthropod Vectors
  • Primary vectors are ticks (United States, former
    Soviet Union, and Japan), mosquitoes (former
    Soviet Union, Scandinavia, and the Baltic
    region), and biting flies (United States
    particularly Utah, Nevada, and California and
    former Soviet Union). Examples of specific
    species include
  • Ticks Amblyomma americanum (Lone Star tick),
    Dermacentor andersoni (Rocky Mountain wood tick),
    Dermacentor variabilis (American dog tick),
    Ixodes scapularis, Ixodes pacificus, and Ixodes
    dentatus
  • Mosquitoes Aedes cinereus and Aedes excrucians
  • Biting flies Chrysops discalis (deerfly),
    Chrysops aestuans, Chrysops relictus, and
    Chrysozona pluvialis

21
Francisella tularensisMorphology and Physiology I
  • Small, weakly staining gram-negative
    coccobacillus 0.2 to 0.2 0.7 um in size.
  • Nonmotile, displays bipolar staining with Giemsa
    stain, obligate anaerobe, and is weakly catalase
    positive.
  • Young cultures are relatively uniform in
    appearance while older cultures display extreme
    pleomorphism.
  • Carbohydrates are dissimilated slowly with the
    production of acid but no gas.
  • Displays a thick capsule whose loss is
    accompanied by loss of virulence.

22
Francisella tularensisMorphology and Physiology
II
  • The lipid concentration in the capsule and cell
    wall (50 70, respectively) is unusually high
    for a gram negative organism.
  • The lipid composition is unique with relatively
    large amounts of long-chain saturated and
    monoenoic C20 to C26 fatty acids as well as alpha
    and beta hydroxyl fatty acids.
  • Biochemical characterization is of little value
    in identification (other tests are utilized).

23
Francisella tularensisCulture Characteristics
  • Optimal growth at 370 C, growth range 240 to 390
    C. Survival rate is best at lower temperatures.
  • Slow growing with a requirement for iron and
    cysteine or cystine.
  • No growth on routine culture media but small
    colony growth after 2 - 4 days on
    glucose-cysteine-blood agar or peptone-cysteine
    agar.
  • No true hemolysis on blood containing media only
    a greenish discoloration.

24
Francisella tularensisMicrobial
Genomics-Introduction
  • Little is known about the cellular and molecular
    modes of infection, proliferation and immune
    response to tularemia.
  • Microbial genomics has begun to hopefully shed
    some light on the above mechanisms.
  • The lack of adequate genetic tools has hampered
    efforts to elucidate many questions about F.
    tularensis most importantly how it enters cells
    and the factors required for intracellular
    growth.
  • At present most of the genome of F. tularensis
    ShuS4 (high virulence) has been sequenced,
    compiled into contigs and is available at the
    web site http//artedi.ebc.uu.se/Projects/Francise
    lla/

25
Francisella tularensis Microbial
Genomics-Intracellular Growth Genes I
  • Five genetic loci with the use of transposon
    mutagenesis have been identified in F. novicida
    that are associated with intracellular growth.
  • Gene 1 Alanine racemase catalyzes the
    reversible conversion of the L form of alanine to
    the D form. Potential effect Alter bacterial
    cell wall making it more susceptible to
    microbiocidal agents produced by macrophages.
  • Gene 2 Glutamine phosphoribosylpyrophosphate
    amidotransferases (50 identity at a.a. level)
    which catalyzes the first step in de novo purine
    biosynthesis. Potential effect Inhibition of de
    novo purine biosynthesis.

26
Francisella tularensis Microbial
Genomics-Intracellular Growth Genes II
  • Gene 3 ClpB (60 identity to E.coli protein) an
    ATP-dependent protease stress response protein
    which hydrolyzes casein and is part of a system
    which hydrolyzes denatured proteins.
    Potential effect Inhibit the
    removal of denatured proteins overwhelming cell.
  • Gene 4 23Kd protein (99 identity) unique to
    Francisella as the dominantly induced protein
    after infection.
    Potential effect
    Unknown.
  • Gene 5 AF374673 no significant similarity to any
    protein with a known function.
    Potential effect Unknown.

27
Francisella tularensis Microbial
Genomics-Intracellular Growth Genes III
  • The five genes found to be involved in
    intracellular growth all map using the available
    genomic sequence map to the intracellular growth
    locus iglABCD.
  • The iglABCD is a putative operon involved in
    intracellular growth and it is possible that all
    of the proteins encoded by the iglABCD operon are
    needed for intracellular growth and some are
    thought to be transcription factors.
  • The predicted molecular masses of the protein
    products from these genes corresponds to the
    masses of the observed proteins expressed during
    intracellular growth.
  • These observations suggest that these proteins
    play a critical role in the intracellular growth
    of F. tullarensis.

28
Francisella tularensisMicrobial Genomics-Tools
  • Yet another odd characteristic of F. tularensis
    is the absence of its own plasmids in any of the
    biovars. It is not clear whether this property is
    associated with the environment of the bacterium
    or with the specificity of its genetic apparatus.
  • It has been shown that heterologous plasmids can
    replicate in F. tularensis but must be maintained
    by antibiotic resistance selection.
  • One isolate, F. novidica-like strain F6168, is
    the only member of the genus that carries a
    native plasmid and this plasmid has no known
    function or gene products.
  • The 3990-bp cryptic plasmid from F6168 has been
    used to construct two recombinant plasmids,
    pFNL10 and pOM1. These plasmids were engineered
    to contain antibiotic selection genes, a
    polylinker for cloning, and the ori (origin of
    replication) from F6168. A third plasmid pKK214
    has been designed to assay promoter activity.
  • These plasmid tools will hopefully help to
    elucidate some of the mechanisms of intracellular
    growth and virulence.

29
Francisella tularensis Microbial
Genomics-Identification
  • Extensive allelic variation in the short sequence
    tandem repeat, SSTR, (5-AACAAAGAC-3) has been
    found among F. tularensis.
  • With the use of appropriately designed primers
    and conditions it is possible through the use of
    PCR to identify individual strains.
  • The analysis of the SSTRs is a powerful tool for
    the discrimination of individual strains and
    epidemiological analysis.

30
Francisella tularensis Detection Methods
  • PCR is a rapid accurate detection method that can
    distinguish between strains.
  • ELISA has been used and various antibody labeling
    methods can be used for detection.
  • Time resolved flourometry (TRF) assay system is
    more accurate and sensitive than the ELISA method
    and requires at least two hours to perform.
  • Mass spectroscopy (MS) of whole bacteria and
    isolated coat proteins has also been developed.
    In a clinical lab it is feasible but new portable
    MS systems are still unreliable in the field.

31
Francisella tularensis New Detection Methods I
  • New detection methods should be easy to use,
    practical, accurate, highly mobile and developed
    in a minimum amount of time.
  • Unfortunately development of instrumentation
    takes 2-5 years and costs millions of dollars.
  • The use of already tested, off the shelf
    components would greatly reduce development time
    and cost, time being most important in light of
    recent events.

32
Francisella tularensis New Detection Methods II
  • A cheap easy to use detection system could be
    assembled from the following existing products to
    perform quick accurate PCR analysis to identify
    individual Francisella strains.
  • Bacteria would be lysed in water at 940 C for 2
    minutes? PCR using a capillary light cycler( 25
    cycles in less than 10 minutes) ?resolve products
    on either low percent pre-cast gel (visual
    identification) or fluorescent capillary
    electrophoresis (detection via labeled primer)
    (5-10 min)
  • Entire process less than 20 minutes and cost from
    15-50 thousand dollars.
  • Requires power 120V, 10amps so can be transported
    and operated in a light truck or helicopter.

33
Francisella tularensisImmunology-I
Internalization
  • The mode of infection, proliferation, and the
    immune response to tularemia are still not well
    defined. The cells targeted are the macrophages
    and parenchymal cells.
  • The mode of entry into cells is still unknown but
    it is thought to be similar to the Listeria
    monocytogenes, another intracellular bacteria.
  • The mode of entry utilized by L. monocytogenes,
    the zipper-type mechanism in which bacterial
    surface proteins bind to host cell surface
    receptors and the bacteria are internalized.
  • In L. monocytogenes the E-cadherin has been
    identified as the host cell receptor involved,
    but to date no receptor has been identified for
    Francisella internalization.

34
Francisella tularensisImmunology-II Infection
Overview
  • F. tularensis enters the cell.
  • Proliferation inside acidified compartments
    containing iron.
  • High levels of viable bacteria induce
    cytopathagenesis and apoptosis.
  • Inflammatory response due to pathogen entry
    attracts large numbers of macrophages. These
    macrophages are not activated and are easier to
    infect.
  • Due to bacterial capsule, immunity to the effect
    of neutrophils and complement.
  • Renewed infection in arriving macrophages.

35
Francisella tularensisImmunology-III Host Death
  • The accumulation of macrophages without removal
    of bacteria initiate granuloma formation and the
    continued activation of the immune system.
  • Host death due to complications due to pnuemonia
    and/or due to septic shock due to the large
    quantity of cytokines released.
  • Tularemia does not release or contain any known
    toxin that causes disease, but it does usurp the
    immune system and uses it against the host.

36
Francisella tularensis T-cell Activation
Immunology-IV
  • In response to antigen CD4 and CD8 are activated
    and produce interferon gamma (IFN-gamma)
    activating macrophages.
  • The activated macrophages release tumor necrosis
    factor alpha (TNF-alpha).
  • IFN-gamma and TNF-alpha together act to up
    regulate phagocytosis by macrophages, cause them
    to sequester iron within activated macrophages,
    and to up regulate nitrous oxide release, levels
    of which are good indicators of the extent of
    action of this mechanism.

37
Francisella tularensis T-cell Activation
Immunology-V
  • No individual antigen has yet to be identified.
    Hosts recognize a multide of antigens but no
    immuno-dominant antigen.
  • The presence of phosphoantigens have been
    identified in extracts of F. tularensis.
  • Phosphoantigens (alkyl-pyrophoshoesters) are
    potent inducers of the gamma/delta subset of T
    cells causing clonal expansion.
  • The role of the expansion of this subset of T
    cells and the relevance of phosphoantigens as
    vaccine candidates is still unclear.

38
Francisella tularensisImmunology-VI B-cell
Involvement
  • B-cells play a role in the suppression of
    neutrophil mobilization.
  • B-cells are necessary to develop an immune
    response to future encounters with the antigen in
    F. tularensis infection.
  • It is not thought that the production of specific
    antibodies play a large part in the response.
  • IgM and low levels of IgG are detected early
    (3-10 days after infection) and are thought to
    confer early protective as well as long term
    immunity.
  • Immune responses appear primarily to be in
    response to the lipopolysaccharide (LPS) of the
    outer membrane of the bacterium which appears to
    be the major protective antigen.

39
Francisella tularensisImmunology-VII B-cell
Involvement
  • This year the composition of the core LPS
    proteins have been uncovered. The composition of
    the core, lipid A and the O-side chain of F.
    tularensis have been found to have a unique
    compositions that does not confer host protection
    upon exposure.
  • Only the intact LPS has been found to induce a
    protective immune response.

40
Francisella tularensisConclusions
  • The ongoing sequencing of the SCHU S4 and LVS
    Francisella have resulted in a large increase in
    information included targets that can be used for
    the generation of attenuated strains.
  • Large scale proteomic work has begun.
  • Together the genomic and proteomic investigations
    will lead to the development of new strategies
    for genetic manipulation and hopefully lead to an
    understanding of the virulence mechanisms of this
    potent pathogen.

41
Francisella tularensis
  • Organisms are strict aerobes that grow best on
    blood-glucose-cysteine agar at 37C
  • Facultative, intracellular bacterium that
    multiplies within macrophages
  • Major target organs are the lymph nodes, lungs,
    pleura, spleen, liver, and kidney

42
Tularemia
  • Contagious --- no
  • Infective dose --- 10-50 organisms
  • Incubation period --- 1-21 days (average3-5
    days)
  • Duration of illness --- 2 weeks
  • Mortality --- treated low untreated
    moderate
  • Persistence of organism ---months in moist soil
  • Vaccine efficacy --- good, 80

43
Two subspecies
  • Type A tularensis
  • Most common biovar isolated in North America
  • May be highly virulent in humans and animals
  • Infectious dose of less then 10 CFU
  • Mortality of 5-6 in untreated cutaneous disease
  • Type Bpalaeartica (holartica)
  • Thought to cause all of human tularemia in Europe
    and Asia
  • Relatively avirulent
  • Mortality of less then .5 in untreated cutaneous
    disease

44
7 Forms of Tularemia
  1. Ulceroglandular
  2. Glandular
  3. Oropharyngeal (throat)
  4. Oculoglandular (eye)
  5. Typhoidal
  6. Septic
  7. Pneumonic

45
Mortality Rates
  • Overall mortality rate for Severe Type A strains
    is 5-15
  • In pulmonic or septicemic cases without
    antibiotic treatment, the mortality rate has been
    as high as 30-60
  • With treatment, the most recent mortality rates
    in the U.S. have been 2

46
Infection
  • Routes of Infection
  • No human to human transmission
  • Inhalation (fewer than 30 organisms)
  • Ingestion
  • Incisions/Abrasions (fewer than 10 organisms)
  • Entry through unbroken skin
  • Example Ulceroglandular Tularemia
  • Transmitted through a bite from an anthropod
    vector which has fed on an infected animal

47
Transmission
  • Organisms are harbored in the blood and tissues
    of wild and domestic animals, including rodents
  • In US chief reservoir hosts are wild rabbits and
    ground squirrels

48
Transmission
Route of Transmission Mode of Transmission
Skin or conjunctiva Handling of infected animals
Skin Bite of infected blood-sucking deer flies and wood ticks
GI tract Ingestion of improperly cooked meat or contaminated water
Respiratory tract Aerosol inhalation
49
Infection
  • Incubation Period
  • 1-14 days, dependent on route and dose
  • Usually 3-5 days
  • Ulceroglandular and glandular tularemia are
    rarely fatal (mortality rate lt 3)
  • Typhoidal tularemia is more acute form of disease
    (mortality rate 30-60 )

50
Symptoms
  • Immediate Symptoms
  • Fever, headache, chills, rigors, sore throat
  • Subsequent Symptoms
  • Loss of energy, appetite, and weight
  • Rare Symptoms
  • Coughing, chest tightness, nausea, vomiting,
    diarrhea

51
Symptoms and Reaction
  • Symptoms are severe enough to immobilize people
    within first two days of infection.
  • Symptoms depend on route of infection.
  • Have localized reaction when there is a specific
    infection site (cut, tick bite).
  • Localized infection can develop into systemic
    infection through haematogenous spread.

52
Symptoms by Route of Infection
  • Aerosol or Ingestion
  • Systemic infections, no localized ulcers or lymph
    gland swelling
  • Aerosol
  • Pneumonia
  • Ingestion
  • Gastrointestinal irritation
  • Localized
  • Enlargement of local lymph glands, ulcer at
    infection site

53
Outbreaks
Chest X-ray of patient demonstrating complete
whiteout of the left lung
54
Tularemia Lesion
55
Skin Ulcer of Tularemia
56
Diagnosis
  • Confirmed by
  • Successful culture of bacteria
  • Significant rise in specific antibodies
  • Problems with above methods
  • Culture is difficult and dangerous
  • Response from antibody does not occur until
    several days after onset of disease

57
Future Diagnostic Techniques
  • New PCR based technique produces higher success
    level for identification than culturing currently
    does.
  • Future tests may allow for identification of the
    specific strain infecting a patient.
  • Could be useful for a bioterrorist attack.

58
Prevention
  • Best Immunity (Permanent)
  • Previous infection with a virulent strain
  • Dr. Francis
  • Live Vaccine Strain (LVS)
  • Best prophylactic
  • Foshays Vaccine (killed bacteria)
  • Provides lesser immunity towards systemic and
    fatal aspects of disease than LVS

59
Prevention and Treatment
  • Vaccines take too long to have an effect, so
    cant be used for treatment after exposure
  • Antibiotics are effective for treatment after
    exposure
  • Antibiotic treatment must begin several days
    post-exposure to prevent relapse

60
Live Vaccine
  • Live Virus Strain (LVS)
  • Pros
  • Only effective vaccine against tularemia
  • Cons
  • Doesnt provide 100 immunity
  • Possibility of varying immunogenicity between
    different batches
  • Possibility of a spontaneous return to virulence

61
The incidence of acute inhalational Tularemia
Use of a killed vaccine 5.70 cases per 1000 people at risk
Use of a live vaccine 0.27 cases per 1000 people at risk
62
Antibiotics to Treat Tularemia
  • Streptomycin and aminoglycoside gentamicin
  • Pros
  • Effective against tularemia
  • Cons
  • Require intramuscular or intravenous
    administration
  • High toxicity profile
  • Can be relapses of tularemia on aminoglycosides
  • There exist streptomycin-resistant strains of F.
    tularensis

63
Antibiotics to Treat Tularemia
  • Tetracyclines and chloraphenicol
  • Pros
  • Effective against tularemia
  • Can be administered orally
  • Low toxicity
  • Cons
  • Higher relapse rate than aminoglycosides

64
Antibiotics to Treat Tularemia
  • Quinolines (including ciprofloxacin)
  • Pros
  • Generally works well
  • Low relapse rate
  • Can be administered orally
  • Cons
  • Has not been used extensively for treatment

65
Outbreaks
  • No large recorded outbreaks of inhalational
    tularemia in United States
  • Single cases or small clusters including
  • Laboratory exposures
  • Exposure to contaminated animal carcasses
  • Infective environmental aerosols

66
Outbreaks
  • Laboratory Workers
  • Began with a fatal case of pulmonary tularemia in
    a 43 year old man
  • Total of 13 people in the microbiology laboratory
    and autopsy services used were exposed despite
    adhering to established laboratory protocol
  • Services should have been notified of possibility
    of tularemia
  • Tularemia ranks second in the US and third
    worldwide as a cause of laboratory associated
    infections

67
Outbreaks
  • Sweden 1966-1967
  • More than 600 patients infected with strains of
    milder European biovar of F. tularensis
  • Farm work created aerosols which caused
    inhalational tularemia
  • Cases peaked during the winter when
    rodent-infested hay was being sorted and moved
    from field storage sites to barns
  • No deaths were reported

68
Category A Agents
  • Based on probability of use, distribution,
    availability, and risk assessment, the CDC
    specified 6 agents that have the highest
    likelihood of successful use
  • Anthrax
  • Plague
  • Tularemia
  • Botulinum toxin
  • Smallpox
  • Viral Hemorrhagic Fevers

69
Bioterrorism Agents Laboratory Risks
  • Agent BSL Laboratory Risk
  • B. anthracis 2 Low
  • Y. pestis 2 Medium
  • F. tularensis 2/3 High
  • Botulinum toxin 2 Medium
  • Smallpox 4 High
  • VHF 4 High

70
Why Use Tularemia?
  • Col. Gerald Parker, director of USAMRIID
  • Ideal agent has availability, easy production,
    high rate of lethality or incapacitation,
    stability, infectivity, and aerosol
    deliverability
  • Tularemia and anthrax most potent by far, with
    the least amount necessary for a 50 kill in a 10
    km area

71
However
  • Col. Parker went on to prioritize smallpox and
    anthrax first for probable use, followed by
    plague and tularemia, followed by botulinum toxin
    and hemorrhagic fever viruses

72
Anthrax v. Tularemia
  • U.S. test involving dropping light bulbs on the
    subway tracks
  • Observed amount of bacteria seen throughout the
    system
  • Numbers of passengers per train
  • Average time per person spent on the subway
  • 12,000 cases of anthrax
  • 200,000 cases of Tularemia

73
  • I know of no other infection of animals
    communicable to man that can be acquired from
    sources so numerous and so diverse. In short, one
    can but feel that the status of Tularemia, both
    as a disease in nature and of man, is one of
    potentiality.
  • R. R. Parker

74
History of use as a Biological Weapon
  • During WWII, its potential use was studied both
    by Japan and by the U.S. and its allies
  • In the 1950s and 1960s, the U.S. developed
    weapons that could deliver aerosolized organisms
    of F. tularensis
  • It was stockpiled by U.S. military in the late
    1960s, and the entire stock was destroyed by 1973
  • The Soviet Union continued weapons production of
    antibiotic and vaccine resistant strains of F.
    tularensis into the early 1990s.

75
High Exposure to Infection Rate
  • 2500 spores to cause inhalational anthrax
  • Fewer than 10 organisms for intracutaneous
    tularemia infection
  • Fewer then 30 F. tularensis organisms through an
    aerosol

76
Indications of intentional release of biologic
agent
  • An unusual clustering of illness (temporal or
    geographical)
  • An unusual age distribution for common diseases
  • Patients presenting with clinical signs or
    symptoms that suggest an infectious disease
    outbreak

77
  • Outbreaks of pneumonic tularemia,
    particularly in low incidence areas, should
    prompt consideration of bioterrorism

78
Can assume bioterrorism if
  • There is an abrupt onset and a single peak of
    cases
  • Among exposed people
  • Attack rates would be similar across age and sex
    groups
  • Risk would be related to degree of exposure to
    the point source
  • Rapid progression of a high proportion of cases
    from upper respiratory symptoms to life
    threatening pleuropneumonitis
  • An outbreak of inhalational tularemia in an urban
    setting

79
World Health Organization Study
  • In the event that a tularemia mass casualty
    biological weapon was used against a modern city
    of 5 million people
  • an estimated 250,000 people would get
    sick, and 19,000 people would die

80
Economic impact
  • Referring to this model, the CDC examined the
    expected economic impact of bioterrorist attacks
    and estimated the total base costs due to an F.
    tularensis aerosol attack to be 5.4 billion for
    every 100,000 people exposed

81
Would expect
  • Short half-life due to
  • Desiccation
  • Solar radiation
  • Oxidation
  • Other environmental factors
  • Limited risk from secondary dispersal

82
Vaccine
  • A vaccine for Tularemia is under review by the
    FDA and is not currently available in the U.S.
  • Because of the 3-5 day incubation period, and
    post-vaccination immunity takes two weeks to
    develop, post exposure vaccination is not
    considered a viable public health strategy to
    prevent disease in the event of mass exposure

83
  • Careful proactive initiation of post exposure
    prophylaxis should not be underestimated for its
    medical, public health, psychological and
    political merits in coping with a terrorist
    attack.
  • Center for Infectious Disease

84
Postexposure Prophylaxis
  • One study involving volunteer subjects
    demonstrated that use of tetracycline within 24
    hours after exposure can prevent disease
    occurrence

85
for inhalational tularemia
  • If release of the agent becomes known during the
    incubation period, people in the exposed
    population should be placed on oral doxycycline
    or ciprofloxacin for 14 days
  • If release does not become apparent until the
    appearance of clinical cases, potentially exposed
    people should be placed on a fever watch

86
what would happen?
  • Any person in whom fever or flu like illness
    develops should be evaluated and placed on
    appropriate antibiotic therapy for treatment of
    tularemia
  • Parenteral therapy in a contained casualty
    setting
  • Oral therapy in the mass casualty setting
  • Treatment should continue for fourteen days

87
Where are these helpful items coming from?
  • Antibiotics for treating patients infected with
    tularemia in a bioterrorism scenario are included
    in a national pharmaceutical stockpile maintained
    by the CDC, as are ventilators and other
    emergency equipment

88
Where antibiotics fail
  • There is a possibility that genetically induced
    antibiotic resistant strains could be used as
    weapons
  • Should be considered if patients deteriorate
    despite early initiation of antibiotic therapy
  • This increases the need to create a test which
    could rapidly identify the antibiotic
    susceptibility of tularemia strains

89
Genetic Manipulation
  • Scientists generated a plasmid to insert
    resistance genes for tetracycline and
    chloraphenicol
  • Plasmid was capable of replicating within F.
    tularensis and E. coli

90
Genes to be worried about
  • Antibiotic resistance
  • Radiation resistance
  • Desiccation resistance
  • Genes that code for toxins from other bacteria
  • Genes that would decrease the incubation time of
    tularemia

91
Possible Vaccines
  • The construction of a defined attenuated mutant
    of F. tularensis could provide a safe, effective,
    and licensable tularemia vaccine that could
    induce protective immunity
  • The construction of a vaccine that does not use a
    live pathogen

92
Its critical to develop
  • Simple, reliable, and rapid diagnostic test to
    identify F. tularensis in people
  • Fast and accurate procedures to quickly detect F.
    tularensis in environmental samples
  • A system to monitor for the appearance of
    antibiotic resistant strains
  • New, effective antibiotic

93
To Prevent Infection
  • Isolation would not be helpful given lack of
    human-to-human transmission
  • So.
  • Avoid infected animals
  • Wash your hands
  • Wear gloves, masks, face-shields, eye-protection,
    gowns
  • Handle patient equipment with care

94
Dialogue!!!
  • Local practitioners, national health
    organizations, and the international community
    must all communicate to control any outbreak

95
Limitations of Commercial Identification Systems
  • Potential of generating aerosols
  • High probability of misidentification

96
Whos working for our safety?
  • 1970- The US terminated its biological weapons
    development program by executive order
  • 1973- The US had destroyed its entire biological
    arsenal
  • Since then, USAMRIID has been responsible for
    defensive medical research on potential
    biological warfare agents
  • The CDC operates a national program for
    bioterrorism preparedness and response
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