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ARTHROPODBORNE ZOONOSES

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... living organisms on host; pediculosis (louse), scabies (mite), internal (myiasis) bites and stings (venomous insect bites) - spider, scorpion ... – PowerPoint PPT presentation

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Title: ARTHROPODBORNE ZOONOSES


1
ARTHROPOD-BORNE ZOONOSES
  • Rocky Mountain Spotted Fever
  • Typhus
  • Lyme disease
  • Ehrlichiosis

2
TICK-BORNE ZOONOSES
  • Arthropods and Public Health
  • Interaction of host and parasite
  • Diseases associated with direct effect
  • entomophobia - fear of insects revulsion to
    spiders, roaches, earwigs can cause enough
    anxiety to seek medical attention
  • infestation - presence of living organisms on
    host pediculosis (louse), scabies (mite),
    internal (myiasis)
  • bites and stings (venomous insect bites) -
    spider, scorpion
  • contact poison - blister beetle, certain
    caterpillars

3
TICK-BORNE ZOONOSES
  • Arthropods and Public Health
  • Interaction of host and parasite
  • Diseases associated with effects of host,
    parasite, vector
  • man as primary host
  • dengue, typhus, malaria
  • man as incidental host
  • zoonoses plague, leishmania, tularemia,
    hemorrhagic fever
  • once establihsed, may be transmitted from man to
    man by same or different vectors

4
TICK-BORNE ZOONOSES
  • Arthropods and Public Health
  • Interaction of host and parasite
  • Diseases associated with effects of host,
    parasite, vector
  • mechanical transmission - insect picks up agent
    on body surfaces, transmits to humans (flies -
    bacillary dysentery)
  • biological transmission - insect vector not only
    transmits, but is essential in life cycle of
    disease agent

5
TICK-BORNE ZOONOSES
  • Arthropods and Public Health
  • Biological transmission
  • propagative - disease agent grows or multiplies
    in vector without going through cycle
  • cyclo-developmental - disease agent goes through
    essential part of cycle inside arthropod with no
    increase in numbers (ex filiariasis)
  • cyclo-propagative - cycle change and increase in
    numbers (amplification) (ex malaria)

6
TICK-BORNE ZOONOSES
  • Arthropods - Ticks

7
TICK-BORNE ZOONOSES
  • Arthropods - Ticks

8
TICK-BORNE ZOONOSES
  • Arthropods - Ticks

9
TICK-BORNE ZOONOSES
10
ROCKY MOUNTAIN SPOTTED FEVER
  • Other names tickborne typhus, pinta fever
    (Mexico)
  • Agent Rickettsia rickettsii, a rickettsial
    infection
  • a tick-borne zoonosis affecting animals and man

11
RMSF
  • First recognized in 1896 in the Bitter Root
    Valley (Montana), hence the name
  • Major endemic regions
  • South Atlantic states (DE MD to FL) - 50
  • West Central states (AR, OK, LA, TX) - 20
  • Rocky Mountain region accounts for only 2

12
RMSF
  • Microbiological features
  • Rickettsia are small gram negative bacilli
  • Obligate intracellular parasites
  • Two primary groups defined by surface
    antigenicity
  • Spotted-fever group (RMSF, rickettsialpox, etc.)
  • Typhus group (Epidemic, murine, scrub)
  • Scrub typhus now classified under genus Orientia
  • Transmitted by bite of infected ticks or mites

13
RMSF
  • Microbiological features
  • Biochemistry
  • predominately grow within cells
  • many require increased CO2 levels
  • soluble and cell-bound antigens used for
    serological differentiation
  • Virulence factors
  • no enterotoxins formed
  • a lethal toxin has been described for mouse
  • not hemolytic

14
RMSF
  • Microbiological features
  • Rickettsia rickettsii
  • prototype of spotted fever group
  • replicates in nucleus and cytoplasm of infected
    tick and mammalian cells
  • labile, does not survive long under normal
    environmental conditions
  • readily inactivated by heat and chemical
    disinfectants

15
RMSF
16
RMSF
  • Clinical features
  • humans
  • sudden onset of moderate-high fever
  • severe malaise, myalgia and headache
  • conjunctival injection
  • characteristic rash in 50 or cases
  • maculopapular rash on extremities (especially
    soles, palms) on about the 3rd day, spreading
    centripitally within a few days

17
RMSF
  • Clinical features maculopapular rash

18
RMSF
  • Clinical features petechial rash

19
RMSF
  • Clinical features
  • ddx (early RMSF)
  • ehrlichiosis
  • meningococcemia (meningitis)
  • enteroviral infection
  • case fatality rate up to 25 if untreated
  • rarely fatal with treatment, although recently,
    up to 5 of case fatality with proper treatment
  • risk factors delayed Ab therapy and 40 yrs of
    age

20
RMSF
  • Clinical features
  • animals
  • normally subclinical, but can be manifested in
    dogs
  • fever, lethargy, neurological signs,
    lymphadenopathy, splenomegaly
  • petechia observed in 20 of cases

21
RMSF
  • Diagnosis
  • based on clinical signs supported by serology
  • IFA of skin biopsy to detect organism
  • ELISA
  • CF (later)

22
RMSF
  • Epidemiology
  • occurrence
  • normally seen in late spring through the summer
    (April to September)
  • occurs throughout the US, endemic foci southern
    Atlantic and south central
  • more common in males in the West, and children in
    the southeast
  • also documented in Canada, Mexico, Central and
    South America

23
RMSF
24
RMSF
  • Epidemiology
  • Reservoir
  • certain species of Ixodid ticks through
    transovarial and transstadial passage, therefore
    considered principal reservoir
  • broad host range - raccoons, voles, dogs can be
    infected
  • voles play most prominent role as reservoirs for
    horizontal amplification of agent

25
RMSF
  • Epidemiology

26
RMSF
  • Epidemiology
  • mode of transmission
  • bite of tick
  • at least 4-6 hours attachment for rickettsiae to
    become reactivated and infectious
  • contamination of broken skin by crushed tissues
    also possible

27
RMSF
  • Epidemiology

28
RMSF
  • Epidemiology
  • vector
  • Dermacentor variablis (American dog tick) -
    eastern and southern US

29
RMSF
  • Epidemiology
  • vector
  • D. andersonii (Rocky Mountain wood tick) -
    northwest US

30
RMSF
  • Epidemiology
  • vector
  • Amblyomma americanum (Lone Star tick) -
    occassionally in southwest US

31
RMSF
  • Epidemiology
  • vector
  • Rhipicephalus sanguineus (Brown dog tick), A.
    cajennensus - Mexico, Latin America

32
RMSF
  • Exposure
  • peridomestic-dogs bring infected ticks into
    environment
  • recreational
  • occupational

33
RMSF
  • Prevention
  • avoid tick-infested habitats
  • personal protection
  • periodic total body search for presence of ticks
  • early removal of tick (

34
RMSF
  • Prevention
  • Vaccination
  • killed or attenuated live vaccines available, but
    limited efficacy
  • have been recommended for high risk individuals
  • recombinant DNA methodology now being investigated

35
RMSF
  • Control
  • interruption of peridomestic cycle
  • tick control
  • active surveillance of ticks and wildlife
  • to monitor changes in the distribution
  • to provide early detection
  • to determine risk indices
  • to provide prevalence data to evaluate
    effectiveness of prevention programs
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