• intracellular organisms
  • obligate intracellular except for Coxiella burnetti
  • fastidious
  • pleomorphic coccobacilli (stain poorly, but classify gram neg.)
• primarily zoonoses
  • humars are incidental hosts
• produce similar clinical syndromes and require high clinical suspicion for dx
• know areas of endemnicity who are likely bitten

• Q fever
• survival
  • forms spores thar resist desiccation and heat (can be transmitted as aerosols)
  • intracellular, replicate in phagolysosomes of macrophages (loves the acidic envir.)

• lack LPS in cell wall
• infect WBC's
  • form intracellular vacuoles or morulae

• spotted fever group
  • R. rickettsia (Rocky mountain spotted fever)
  • R. conorii
  • R. akari
• typhus group
  • R prowazekii- louse borne typhus (epidemic)
  • R typhi- murine typhus (endemic)

1. tick stays attached for 4-48 hrs
2. presymp.
3. bacteremia is point where you become symptomatic
4. you become convalescent

• Dermacentor spp.
  • dog tick
  • adult stage only
  • tick bites often undetected
• usually in summer
• endemic in in US, Canada, Mexico, Central America, brazil, columbia

1. tick infects small wild rodents
2. infected adult tick will lay eggs
3. infected eggs grow into larvae
4. larvae take a blood meal on small, wild rodents
5. leads to infected nymph
6. take a blood meal to infect small wild rodents

Humans incidentally infected by bite of adult tick

1. tick bite intro bacteria to skin
2. spread via lymphatics, small bv's
3. target vascular endothelial cells by attaching to outer membrane protein A (Omp A)
4. ricketsia phagocytosed, escape from phagosome into cytosol
   1. prolif. intracelluarly
   2. release via thin cell projections extracellularly or adjacent to cell walls
5. direct vascular injury, increased vascular permeability: edema, hemorrhage, hypotension
6. express platelet binding substances
   1. activate coagulation system
   2. consumption of platelets, leading to thrombocytopenia

• classic triad: fever, headach, rash
• rash starts peripherally (ankles, wrist) and spreads centrally
• if severe: hemorrhagic, cause necrosis of digits

• high risk: black males with G6PDH deficiency, elderly, chronic alcoholism

• mainly clinical: presentation, epidemiology clues
• tx: antibiotics
• serology to confirm
  • increase IgG
  • Ab appear 10-14 days after infection
• immunohistochemical stains

• cover up
• use repellents
• examine skin for ticks frequently
• know seasons, area of risk

Applies to all tick born diseases

• Africa, Meditteranian, Middle East

• mainly found in Southern Africa
• tick borne
• onset: fever, headache, myalgias
  • tache noire very common at tick bite (black spot)
  • eschar with surrounding swelling
• severe disease ONLY with underlying disease (DM, alcoholics)
• otherwise, it will self resolve

• reservoir- mice
• transmitted to humans by mites
  • bites usually painless
  • homeless population at risk
• eschar at mite bite appearing before systemic symptoms
• followed by abrupt onset of fever, chills, headaches, vesiculopapular rash
• complications and death are rare

• transmitted person to person via body louse (vector)
• assoc. with crowded, unsanitary conditions (refugee camps, prisons), war, famine, natural disasters
• usually cold climates, during fall winter months (clothing less likely to be changed)
• human most common reservoir, also found in flying squirrel

• louse becomes infected by feeding on infected humans
  • louse alimentary tract becomes infected
• when louse takes blood meal it deficates
  • irritation cause host to scrate, inoculating bite would
  • infection also through mucous membrane
• louse eventually die from intestinal obstruction

• onset: 7-10 days
• maculopular rash develops 3-5 days after ever
  • usually does not involve palms, soles, face
• high mortality esp. in elderly

• can relapse after many years with wanning immunity or immunosup.
• Brill Zinsser Disease

• mainly clinical suspicion
• tx- doxycycline

• transmitted by fleas from rats with R. typhi
  • coastal urban areas with poor rodent control
  • bite rarely reported
  • endemic in southern Cali, Texas in summer, early fall
    • also cats, possums
• worldwide zoonosis
• only mild clincal illnes

• incubation- 1-2 wks
• rash usually on extremities
  • mostly maculopapular

• serology
  • Felix Weil agglutination (test for Ab's)
    • also agglutinate some Proteus vulgaris
• tx- doxycycline
• prevent by control vector (fleas) and reservoir (cats)

• only in eastern and SE Asia, Austrailia
• vector is chiggers (larval stage of mites)
• reservoirs are rodents and chiggars (transovarial transmission
• humans acccidental host (travelers, military)

clinical symptoms of scrub typhus

• HALLMARK- regional lymphadenopathy before systemic symptoms
• papule at site ulcerates, eschar develops
• chiggar feeds on host, inoculates at site of bite
• incubation- 10-14 days
• can have CNS complications
  • delirium
  • deafness
  • aggitation
• usually resolve spontaneously in 2 wks

• PCR available
• clinical suspicion
• tx- doxycycline

• more related to Legionella, Francisella
• intracellular organism
  • infects macrophage where multiply in phagolysosome
• undergo sporulation
  • allow survival in external environment
  • survives harsh conditions (cold, heat)
  • disseminated as an aerosol
• highly infectious- takes only one organsim to cause infection

• worldwide
• zoonosis esp. cows, other farm animals
• shed in urine, feces, milk of infected animal
  • infection reactivate during preg., cause abortions in animals
• occupational risk of farmers, livestock animals, veterinarians

• incubation of 2-5 wks
• only humans manifest disease
• severity depends on inhaled dose
• acute: self limited (less than 2 weeks)
  • pneumonia (usually atypical)
• chronic (more than 6 months)
  • endocarditis (negative blood cultures with subacute presentation)
  • osteomyelitis
  • more common in immunocompromised

• dangerous and difficult to culture the organism
• acute infection usually resolves spontaneously
• chronic infection treated for 18 months with a combination of antibiotics
• serology to dx (positive within 1-2 wks of disease onset)

Coxiella burnetti

Rickettsia prowazeki

• emerging tick born infections
• obligate intracellular parasites
  • Ehrlichia and Anaplasma
  • species that cause disease
    • E. chaffensis
    • Anaplasma phagocytophilum
• infect leukocytes
  • type of WBC depend on species
  • bacteria form vacuoles or morulae (clusters of bac.)

• tick born infection
• usually summer peaks
• Ixodes scapularis and Ambylomma americanum (lone star tick) each have diff. species of bact.

• vector- Amblyomma americanum aka tick
• infect humans, white tailed deer
• found in south central, south east, mid atlantic states

• vector- Ixodes scapularis (also cause Lyme, babesiosis)
• found in US, Europe, Asia
  • US- NE, mid atlantic, upper midwest, pacific northwest
• reservoir- rodents, small mammals

1. tick bite innoculate
2. lymphatic dissemination
3. target WBCs in blood, bone marrow, tissues
4. recog. receptors, internalize, survive/multiply within morulae (inh. fusion with lysosomes
5. cause leukopenia and thrombocytopenia
6. direct cytopathic effect and interferes with immunologic response

• incubate: 7-10 days
• maculopapular rash
• complication with immunocompromised
  • within days of onset or rarely later
  • septic shock like syndrome
  • meningits, meningoencephalitis
  • may cause death

• incubation 7-14 days
• differs from HME w/
  • rash uncommon
  • rare CNS involvement
  • peripheral neuropathies common (facial palsy, brachial plexopathy
  • death rare
• similar lab findings: leukopenia, increased liver enzymes, thrombocytopenia

• mainly infects dogs
• can be transmitted to humans through tick bite
• infects neutrophils
• fewer complications and no fatalities

• clinical- tx with doxycycline
• clinical suspicion needed- h/o tick bite leukopenia, elevated liver enzymes
• peripheral blood smear finding morulae
• PCR amplication
• serology (IFA)- 4x increase in convalescent titer