28 Spirochetes Rickettsia

8/4/2019 28 Spirochetes Rickettsia

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Lecture organization

Some Rickettsiae and

spirochetes are zoonoses Which lecture covers

them? Rickettsieae and

spirochetes orZoonoses?


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Which topics, which lectures

Rickettsiae &

spirochetes

Rocky MountainSpotted Fever

Rickettsial

biology Rickettsioses

Lyme

Zoonoses

Tick biology

Other tickborne

diseases


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Why Rocky Mountain

Spotted Fever? Prototype rickettsiosis

Main reason for deaths?


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Etiology: Invertebrates

1. Rickettsia rickettsiae

2. Ticks (tolerate infection) Dermacentor andersonii,

D. variabilis (hard)

Transstadial, transovarialtransmission


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Etiology: Vertebrates

3. Reservoir

Small rodents (squirrels)

Tolerate infection4. Humans

Intruders into wildlifecycle

Dead-end hosts


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Etiology

Microbe R. rickettsii

Vector Tick

Reservoir Rodents

Host Intruder


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Rocky Mountain Spotted Fever,

4 dots/case, US, 1999


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Monthly Cases, US, 1999

0

25

50

75

100

125

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec


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cases/100,000, by age, US, 1999

0

0.1

0.2

64


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Person

Outdoor activity

Peak age 5-9

Mortality highest

in elderly


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cases/100,000 per year, US

0

0.2

0.4

0.6

1955 1965 1975 1985 1995


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Development of illness

Inoculation

Rickettsemia Endothelial localization

Vasculitis


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Clinical recognition

Rash

Fever

Headache

Other


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Fever and headache

Fever

102 to 105 degrees

2 to 3 weeks without

treatment Headache: severe


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Rash

Fever Headache

Other


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Rash

Fever Headache

Other


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Laboratory diagnosis

Skin biopsy:immunofluorescent stain

SerologyWeil-Felix archaicImmunofluorescent

antibody No growth on routine culture


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Prevention

Vector control impractical

Vaccine unavailable So . . . caution outdoors

Long clothing

Skin inspection


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Rocky Mountain Spotted Fever

Physician suspicion crucial

R. rickettsii, ticks

Not just Rockies Vasculitis

Rash, fever, headache Doxycycline, look for ticks


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Rickettsiae & spirochetes

Rocky Mountain Spotted

Fever

Rickettsial biology

Other rickettsioses

Spirochetes


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Rickettsial biology:

Bacteria . . . or viruses? Antibacterials

Cell membrane

DNA and RNA

Metabolism

Fission

Most need

host cells


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V C M R B

Lives free 0 0 + +/- +Antibiotic 0 + + + +

Rigid wall +/- +/- 0 + +DNA and RNA 0 + + + +

Makes ATP 0 0 + + +Ribosomes 0 + + + +


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OrderRickettsiales

Family Rickettsiaceae

Tribe Rickettsiae

Genus Rickettsia

Genus Coxiella

Genus Rochalimaea

Family Bartonellaceae


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RickettsiaEhrlichia

Bartonella

Coxiella


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Rickettsial groups

Spotted fever groupRocky Mountain Spotted Fever

Other spotted fevers

Rickettsialpox

Typhus group

Epidemic typhus, Brill-Zinsser

Murine, scrub typhus


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Rickettsial properties

Coccobacillary, < 1 micron

Gram stain poorly, needGimenez

Have metabolic apparatus

Use host ATP, NAD, CoA Extracellular survival poor,

need vectors


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Rickettsial biology

Bacteria, not viruses

Clinical grouping Small, poor on Gram

Have metabolic paths

Perish outside cells


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Fever

Rickettsial biology

Other rickettsioses

Spirochetes


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Other rickettsioses

Characteristics of a

typical rickettsial disease Diseases other than


Fever


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Rickettsial epidemiology

Tick vectors (exceptions: typhus,

rickettsialpox)

Humans dead-end hostss

(exception: epidemic typhus)

Mid-spring/mid-summer peak

Vector digestive tract


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Typical rickettsial illness Inoculation eschar

(exception: Rocky MountainSpotted Fever)

Rickettsemia Endothelial growth

Vasculitis 1-2 week incubation Rash, fever, headache


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Rickettsial diagnosis

Must suspect clinically Immunoflorescent stained skin

biopsy Weil-Felix pass Serology usually (but delay in

getting results) Isolation hazardous Rule out others


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Rickettsial control

Public health

Reporting

Vector/reservoir

No vaccines


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Rickettsial diseases other than

Rocky Mountain Spotted Fever

Other spotted fevers (inother parts of world) Rickettsialpox (urban, from

mice and mites) Typhus group (epidemic

typhus from lice)


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Other rickettsioses

Vector (often tick)

Eschar, rickettsemia Vasculitis, serologic test

Includes spotted fevers,rickettsialpox, typhusgroup


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Fever

Rickettsial biology

Other rickettsioses

Spirochetes


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Vincents infection/Trench mouth

Necrotizing ulcerative gingivitis

Synergistic gum infection

Occurs in poor oral

hygiene, malnutrition,

immunocompromise

Penicillin, oral hygiene


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Relapsing Fever

Epidemic Endemic

B. recurrentis Lice

Human-lice

E. Africa,

Andes

Borrelia spp Ornithodoros tick

Human intruder

Worldwide: High,

warm, humid


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Relapsing fever

pathogenesis Spirochetemia

Sequestration Antigenic modification

Widespread (liver, spleen,CNS, heart, GI, kidney)


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Relapsing fever presentation

Abrupt fever, malaise,

headache

Arthralgia, cough, photophobia

Conjunctival suffusion

Petechiae

Abdominal tenderness


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Relapsing fever

Recovery in 3-6 days

Relapse in 7-10 days

Untreated, 40% die

Blood smear positive 70%

Tetracycline,chloramphenicol


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Lyme disease, United States

L di b t US 1999


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Lyme disease by county, US, 1999

0

00 1-14 > 15 cases


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North Central Northeast

Lyme disease, by county, 1996

5-9 10-29 >30


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Lyme disease cases

by month, US, 1999

0

1000

2000

3000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec


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Erythema chronicum

migrans


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Early Late

Da-wk Da-mo Mo-yr

ECM Nerve JointJoint Fatigue

Heart


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Lyme diagnosis and

treatment Clinical, with special serology

Treatment depends on stage

Doxycycline, amoxicillin,cefuroxime

IV penicillin or ceftriaxone(later)


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Tick repellent

DEET

Skin, clothingCNS toxicity (directions)

Permethrin: Clothing


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Doxycycline vs. placebo after tick bite,

N Engl J Med2001EM OK

Doxy 1 234

Placebo 8 239

Event OK

47 109

17 136

No one developed extra-cutaneous Lyme disease.

Advice: Treat in high-risk areas.


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Key points: Lyme disease

Tickborne B. burgdorferi

Local: Erythema migrans Dissem: Heart, nerve, joint

Persist: Fatigue, joint Doxycycline, ceftriaxone


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Frontiers of prevention

Vaccine: Withdrawn

Tick avoidance


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Many spirochetes tickborne

Not tickborne

Syphilis: Sex

Leptospirosis: Animal urine;early conjunctival suffusion,later liver & kidneys

Tickborne: Borrelia relapsingfever, change antigens & relapse


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Spirochetal disease parallels

Lyme (& Syphilis)

Initial rash: Erythema chron. mig.

2 stage: Nerves, heart, joints

Late stage: Arthritis, fatigue

Treatment: Penicillin, tetracycline


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Rickettsia and spirochetes

Rocky Mountain SpottedFever

Headache, rash, fever

Tickborne

No growth on routineculture

Doxycycline


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Rickettsia and spirochetes

Other rickettsia

Poor extracellularsurvival

Suspect clinicallyTyphus: humans, lice


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Spirochetes

Sequestration, antigenic

change in relapsing fever Erythema chronicum

migrans, tick in Lyme

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28 Spirochetes Rickettsia

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