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LEC 07 - Vector-Borne Bacterial Infections
Terms in this set (31)
1. Obligate intracellular pathogens
3. Slow replication rates (>8 hr)
4. Arthropod vector
--> louse (prowazekii)
--> dermacentor tick (rickettsii)
Rickettsial - Characteristics
1. Spotted Fever Group (SFG)
--> Rocky Mountain Spotted Fever = rickettsii
--> Also, parkeri = tick-borne and causes a less severe spotted fever.
2. Typhus Group (TG)
--> Prowazekii = epidemic typhus.
--> typhi = flea-borne, and causes murine endemic typhus.
Two Groups of Rickettsia
• Causative agent of RMSF
• Transovarially transmitted.
• 95% of rickettsial disease in U.S.
• High mortality rate if not treated, BUT antibiotics are effective.
Spotted Fever Rickettsiosis (SFR)
1. Disease develops 2 - 14 days after bite.
2. High fever, headache, chills.
3. Rash develops after ~3 days
--> 90% of patients
--> Starts on extremities and spreads to trunk
--> Macular rash to a petechial rash.
4. Can result in circulatory collapse and
multisystem organ failure.
RMSF - Clinical Disease
1. Clinical diagnosis is critical for early intervention.
--> Symptoms and patient history
2. Serology testing unreliable during very early infection.
3. Immunofluorescence and PCR.
RMSF - Diagnosis
--> Treat early to improve outcome (10 - 25% mortality)
2. AVOID TICKS!
RMSF - Treatment & Prevention
1. Cause of EPIDEMIC typhus.
--> Infection kills louse.
3. High mortality rate if not treated, BUT antibiotics are effective.
4. Major cause of wartime disease
Rickettsia prowazekii - General
1. Incubation period ~ 8 days
2. Fever, headache, and rash develop 1 - 3 days later.
3. Rash starts on trunk and spreads to extremities (opposite of RMSF).
--> 20 - 30% if untreated
--> As high as 60% in compromised populations.
5. Brill-Zinsser disease = recrudescent typhus relapse.
Epidemic Typhus - Clinical Disease
• RMSF rash starts on extremities, spreads to trunk.
• Typhus rash starts on trunk, spreads to extremities.
"RMSF on the wRists, Typhus on the Trunk"
RMSF Rash vs. Typhus Rash
1. Clinical diagnosis is very important.
2. Immunofluorescence and PCR.
Epidemic Typhus - Diagnosis
2. Lice control and proper sanitary conditions.
Epidemic Typhus - Treatment & Prevention
1. Emerging tick-borne pathogens
2. Infect and replicate in leukocytes (within vacuole).
3. Ehrlichia chaffeensis
--> Identified at Fort Chaffee, AR
--> Replicates within monocytes and macrophages.
4. Anaplasma phagocytophilum
--> Replicates within granulocytes
5. Antibiotics are effective
--> Fatality is typically associated with underlying patient complications.
Ehrlichia and Anaplasma - Overview
1. Ehrlichiosis (HME)
--> Amblyomma americanum (Lone Star) ticks.
2. Anaplasmosis (HGE)
--> Ixodes sp. (Blacklegged ticks).
Ehrlichia and Anaplasma - Distribution
1. Symptoms develop 1-2 weeks post-tick bite
2. Fever, myalgias, headache
3. Rash can occur during late stages
4. Leukopenia, thrombocytopenia, and elevated serum transaminases are common.
--> Delayed treatment or immunocompromised patient
HME - Clinical Disease
1. Clinical diagnosis is critical
--> Morulae are not always evident
2. Serology and PCR
--> Serology can be complicated by cross-reactivity with other tick-borne pathogens
HME - Diagnosis
2. Tick control and removal
HME - Treatment & Prevention
3. Slow replication (~12 hr)
4. Arthropod vector.
Borrelia - Characteristics
1. B. recurrentis
--> Relapsing fever epidemic (louse-borne)
2. B. hermsii & B. turicatae
--> Relapsing fever endemic (soft tick-borne)
3. B. burgdorferi
--> LYME DISEASE (hard-tick)
Borrelia - Diseases & Vectors
1. Intermittent fever, headache, chills
2. Symptoms begin about 7 days post-exposure.
3. Febrile for ~1 week, afebrile for ~1 week, febrile ~1 week...
4. Endemic (tick-borne) relapsing fever: 3-4 relapses.
5. Epidemic (louse-borne) relapsing fever: 1-2 relapses
Relapsing Fever - Clinical Presentation
1. Patient history
-Travel (western US, Africa, or Central America)
-Occupational or recreational exposure
2. Serology is NOT helpful.
3. Culture is possible, but difficult.
4. Routinely diagnosed by visualization of spirochetes in blood smears stained
with Giemsa or Wright's stain.
--> Must be stained between onset and peak of febrile episode.
Relapsing Fever - Diagnosis
-Tetracyclines or penicillins
-Jarisch-Herxheimer reaction (same as with syphillis)
Relapsing Fever - Treatment
-Rodent and insect control
-Improve personal hygiene and living conditions
Relapsing Fever - Prevention
1. Localized infection at site of tick bite
2. Incubation period ~1 week (range 3-30 days)
3. Develop erythema migrans (e.g. EM) (70-80% of patients).
4. Lesions are red, often with central clearing.
5. Accompanied by general flu-like symptoms.
Lyme Disease - Stage 1
1. Follows Stage 1 within days to a few weeks.
2. Multiple EM lesions may develop
3. Fatigue, malaise, headache, fever, myalgia.
4. 60% of patients
--> Migratory musculoskeletal pain in joints, tendons and muscles is common.
5. 10-20% of patients
--> Neurologic abnormalities; meningitis and cranial neuritis with facial nerve palsy.
--> BILATERAL BELL's PALSY.
6. 5% of patients
--> Cardiac complications
--> Typically atrioventricular HEART BLOCK.
Lyme Disease - Stage 2
1. Chronic infection - "post-Lyme disease syndrome"
2. 6 months to 30 years after infection
3. May follow long periods of latency
4. Chief manifestations include
--> Chronic arthritis (most common in U.S.)
--> Chronic encephalopathy
--> Chronic cardiomyopathy
Lyme Disease - Stage 3
1. Isolation of B. burgdorferi is definitive, but difficult.
- Occasionally demonstrated in blood and tissues.
- Biopsy of EM lesion early during infection.
2. Clinical picture and positive serological response.
3. Serology is less sensitive during early infection...
4. Western blot interpretation is subjective (signal for at least 5 antigens)
Lyme Disease - Diagnosis
1. Depends on the stage
2. Early manifestations and/or Lyme arthritis...
--> Oral doxycycline (also amoxicillin or cefuroxime).
3. Recurrent Lyme arthritis and peripheral/central nervous system involvement.
--> Parenteral treatment - IV ceftriaxone, cefotaxime, or penicillin G.
Lyme Disease - Treatment
-Avoid tick infested areas
-Tick checks (<24 hrs post-bite)
Lyme Disease - Prevention
1. Lone Star tick (Amblyomma americanun)
2. Also, known as Masters Disease
- EM-like lesion at site of tick bite (disseminated EM is rare)
- General fatigue, headache, fever, and muscle pains
- No arthritis, neurologic disease, or chronic symptoms
- Association with Borrelia lonestari has never been confirmed.
STARI: Southern Tick-Associated Rash Illness
1. Clinical and based primarily on the existence of the typical rash.
2. Ideally after a known Lone Star tick bite...
•Lone star ticks are aggressive
•Lone Star ticks are vectors for other bacterial pathogens
-Consider co-infection or other vector-borne pathogens
STARI - Diagnosis
1. Not known whether antibiotic treatment is necessary.
2. Physicians in areas where Lyme
disease is endemic often treat
patients with oral DOXYCYCLINE.
STARI - Treatment
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