Pathogenesis of Rickettsial Pathogenesis of Rickettsial DiseasesDiseases

DAVID H. WALKER, M.D.DAVID H. WALKER, M.D.The The CarmageCarmage and Martha Walls Distinguished Chair in Tropical Diseasesand Martha Walls Distinguished Chair in Tropical Diseases

Professor and Chairman, Department of PathologyProfessor and Chairman, Department of PathologyExecutive Director,Executive Director,

Center for Center for BiodefenseBiodefense and Emerging Infectious Diseaseand Emerging Infectious DiseaseUniversity of Texas Medical BranchUniversity of Texas Medical Branch

Rickettsial Spotted Fevers, Etiologic Agents, and Geographic Distribution

USA, Russia, USA, Russia, Croatia, TurkeyCroatia, Turkey

R. R. akariakariRickettsialpoxRickettsialpox

Europe, Africa, AsiaEurope, Africa, AsiaR. conoriiR. conoriiBoutonneuse feverBoutonneuse fever

North and South North and South AmericaAmerica

R. parkeriR. parkeriAmerican tick bite American tick bite feverfever

Africa, West IndiesAfrica, West IndiesR. africaeR. africaeAfrican tick bite African tick bite feverfever

The AmericasThe AmericasRickettsia Rickettsia rickettsiirickettsii

Rocky Mountain Rocky Mountain spotted feverspotted fever

Geographic Geographic DistributionDistribution

Etiologic Etiologic AgentAgent

DiseaseDisease

Rickettsial Spotted Fevers, Etiologic Agents, and Geographic Distribution

Japan, KoreaJapan, KoreaR. japonicaR. japonicaJapanese spotted feverJapanese spotted feverAustralia, Southeast Australia, Southeast AsiaAsia

R. R. honeihoneiFlinders Island spotted Flinders Island spotted feverfever

Presumably Presumably worldwideworldwide

R. felisR. felisFlea borne spotted Flea borne spotted feverfever

EuropeEuropeR. R. slovacaslovacaTick borne Tick borne lymphadenopathylymphadenopathy

Northern AsiaNorthern AsiaRickettsia Rickettsia sibiricasibirica

North Asian tick North Asian tick typhustyphus

Eastern AustraliaEastern AustraliaR. R. australisaustralisQueensland tick Queensland tick typhustyphus

Geographic Geographic DistributionDistribution

Etiologic AgentEtiologic AgentDiseaseDisease

Rocky Mountain spotted fever United States, 1920 - 2004

Comparison of Rickettsia rickettsii Infections in Brazil and US

4.4% of cases in 4.4% of cases in household with another household with another casecaseCase fatality rate Case fatality rate ∼∼4% 4% (23% pre(23% pre--antibiotic era)antibiotic era)Median fatal course: 11 Median fatal course: 11 days (preantibiotic era) days (preantibiotic era) Pathology seldom shows Pathology seldom shows significant hemorrhage significant hemorrhage (scattered petechiae)(scattered petechiae)

Frequently large clusters Frequently large clusters of casesof cases∼∼ 50%50%∼∼6 days (currently) 6 days (currently) Fatal cases are Fatal cases are frequently a severe frequently a severe hemorrhagic fever.hemorrhagic fever.

USUS BrazilBrazil

1001008888Fever (%)Fever (%)72729595Eschar (%)Eschar (%)005454Multiple eschars (%)Multiple eschars (%)

NANA5151Regional Regional lymphadenopathy (%)lymphadenopathy (%)

R. R. conoriiconorii

R. R. africaeafricae

Agent

Signs and Symptoms of African Tick Bite Signs and Symptoms of African Tick Bite Fever and Boutonneuse FeverFever and Boutonneuse Fever

97974646Rash (%)Rash (%)90905151maculopapular (%)maculopapular (%)101044purpuricpurpuric (%)(%)004545vesicular (%)vesicular (%)2200Deaths (%)Deaths (%)

R. R. conoriiconorii

R. R. africaeafricae

Agent

Signs and Symptoms of African Tick Bite Signs and Symptoms of African Tick Bite Fever and Boutonneuse FeverFever and Boutonneuse Fever

Buea

Muyuka

Tiko

Limbe Douala

Gulf of Guinea

Estuary ofCameroon

DoualaYAOUNDÉ

9º 30`

4°

Study sites of Study sites of African tick bite African tick bite fever in Cameroonfever in Cameroon

African Tick Bite Fever among Africans

Among 234 patients in whom malaria or Among 234 patients in whom malaria or typhoid fever was suspected and ruled typhoid fever was suspected and ruled out, 32% had out, 32% had IgMIgM antibodies to antibodies to Rickettsia africaeRickettsia africae (IFA titers 32 to 2,048).(IFA titers 32 to 2,048).

African Tick Bite Fever among AfricansComparison of Comparison of R. conoriiR. conorii titers and titers and R. R. africaeafricae OmpAOmpA and and OmpBOmpB immunoblotting immunoblotting showed that at least 26 of 75 patients had showed that at least 26 of 75 patients had African tick bite fever. None were African tick bite fever. None were documented to have documented to have R. conoriiR. conorii infections.infections.In a subsequent study, 7 patients were In a subsequent study, 7 patients were diagnosed by real time PCR to have diagnosed by real time PCR to have R. R. africaeafricae infection (fever, 7; headache, 5; infection (fever, 7; headache, 5; myalgia and/or arthralgia 6; rash, 1; myalgia and/or arthralgia 6; rash, 1; pulmonary signs, 2). pulmonary signs, 2).

Documented Human Case of Rickettsia parkeri Infection in USPapules Papules →→ pustules pustules →→ ulcers ulcers →→escharsescharsFever, headache, malaise, Fever, headache, malaise, myalgias/arthalgiasmyalgias/arthalgiasMaculopapular rashMaculopapular rashLymphadenopathyLymphadenopathy

Documented Human Case of Rickettsia parkeri Infection in USEschar biopsy: Eschar biopsy: lymphohistocyticlymphohistocyticvaculitisvaculitis, immunohistochemical detection , immunohistochemical detection of SFG rickettsiaeof SFG rickettsiaeIsolation and PCR identification of Isolation and PCR identification of R. R. parkeriparkeriSerum antibody titer of 2048 to Serum antibody titer of 2048 to R. parkeriR. parkeriby IFAby IFA

Ecology of Tick-Bite Feverin the Western Hemisphere

Arthropod HostArthropod Host--Amblyomma maculatum, A. americanum, A. triste, A. cooperi, A. variegatum ticks

Established Geographic DistributionEstablished Geographic Distribution--U.S., Brazil, Uruguay, French West IndiesU.S., Brazil, Uruguay, French West Indies

AgentAgent-- R. parkeri/R. parkeri/R.africaeR.africae

Uruguayan Tick-bite FeverFever 100%Tender lymphadenopathy 100%Eschar 100%Maculopapular rash 20-50%

Some cases confirmed by IFA for antibodies to SFG rickettsiaeAssociated with R. parkeri-infected Amblyommatriste tick bite

Rev Med Uruguay 17:2; 119-124, 2001

Percentage of Mexican Patients with Different SignsPercentage of Mexican Patients with Different Signsand Symptoms Compared According to the Serologicaland Symptoms Compared According to the Serological

Evidence of SFG Rickettsiosis and Dengue FeverEvidence of SFG Rickettsiosis and Dengue Fever

575770Eye pain405660Chills27a6985aRash336333Nausea676985Headache909495Myalgia9794100Fever

Neither(n=30)

Dengue(n=16)

SFG Rickettsiosis

(n=20)

Symptoms and Signs

Percentage of Mexican Patients with Different SignsPercentage of Mexican Patients with Different Signsand Symptoms Compared According to the Serologicaland Symptoms Compared According to the Serological

Evidence of SFG Rickettsiosis and Dengue FeverEvidence of SFG Rickettsiosis and Dengue Fever

333135Photophobia1038b5bVomiting27615Cough72515Abdominal

pain10610Petechiae365Epistaxis

Neither(n=30)

Dengue(n=16)

SFG Rickettsiosis

(n=20)

Symptoms and Signs

Clinical Manifestations of Clinical Manifestations of Rickettsia Rickettsia felisfelis Infection in Four Patients in the Infection in Four Patients in the State of YucatState of Yucatáán, Mexicon, Mexico

NRNR++00++Abdominal Abdominal painpain

NRNR++00++MyalgiaMyalgia

NRNR++++NRNRFatigueFatigue

NRNR++++NRNRHeadacheHeadache

++++NRNR++FeverFever

++++++++ExanthemExanthem

44332211

Ecology of Flea-borne Spotted Fever

Arthropod HostArthropod Host--Maintained Maintained transovariallytransovariallyin in Ctenocephalides felis

fleas

Established Geographic DistributionEstablished Geographic Distribution--U.S., Mexico, Brazil, Peru, Europe, U.S., Mexico, Brazil, Peru, Europe, Africa, Asia, presumably worldwideAfrica, Asia, presumably worldwide

AgentAgent-- R. felisR. felis

World Distribution of LouseWorld Distribution of Louse--borne borne Typhus Fever at the End of World WarTyphus Fever at the End of World War IIII

Recrudescent TyphusRecrudescent Typhus

Latent human infection with R. prowazekii for years after primary typhus

Waning immunitytheoretically becauseof poor nutrition, age,alcohol, stress, or otherfactors Reactivation of

R. prowazekiiinfection

Rickettsemia

Human body louseacquires R. prowazekiifrom human bloodAfter 5-7 days,

infectious R. prowazekiiare present in the louse feces

Louse leaves febrile patient

Rickettsiae grow inlouse midgutepithelial cells

Locations of Recent Louse-borne Typhus

EthiopiaEthiopia

FranceFrance

PeruPeru

RussiaRussia

AlgeriaAlgeria

CongoCongo

RwandaRwanda

BurundiBurundi

Enormous Epidemic of Louse-borne Typhus during Civil War in Burundi

Outbreaks in louseOutbreaks in louse--infected jail infected jail populations with high incidence and populations with high incidence and 15% case15% case--fatality rate (1995) fatality rate (1995) Diagnosis of typhus in fatal disease of a Diagnosis of typhus in fatal disease of a repatriated Swiss nurse suspected to be repatriated Swiss nurse suspected to be a viral hemorrhagic fever provided a a viral hemorrhagic fever provided a delayed alertdelayed alert

Enormous Epidemic of Louse-borne Typhus during Civil War in Burundi

100,000 cases of typhus in refugee 100,000 cases of typhus in refugee campscampsDoxycycline treatment (March 1997) Doxycycline treatment (March 1997) and and permethrinpermethrin louse control louse control (August 1997) (August 1997)

Dolan PG and Carter DC. Mammalian Species 78:1Dolan PG and Carter DC. Mammalian Species 78:1--6, 19776, 1977

Distribution of Distribution of GlaucomysGlaucomys volansvolans

Contemporary Flying Squirrel-associated Typhus in the U.S.

Fever 100%Headache 81%Maculopapular rash 66%Confusion 44%Myalgia 42%Case fatality ratio 0%

Dengue Syndrome in Mexico

Among 394 suspected cases of dengue fever, 25.1% had antibodies to typhus group rickettsiae

Isolation and genetic and antigenic identification of Rickettsia prowazekii in cayenne ticks in Nuevo Leon

Amblyomma cajennense

Geographic Distribution of Murine TyphusGeographic Distribution of Murine Typhus

Ecology of Murine Typhus

Rickettsial Genomes in DecayRickettsial Genomes in DecayThe coding sequences of most bacterial The coding sequences of most bacterial genomes range from 87 to 94%;genomes range from 87 to 94%;The coding sequences of rickettsial genomes The coding sequences of rickettsial genomes range from 76 to 81%;range from 76 to 81%;229 intact genes of 229 intact genes of R. conoriiR. conorii that have that have remnant sequences in remnant sequences in R. prowazekiiR. prowazekiiR. typhiR. typhi has the most has the most pseudogenespseudogenes (41). (41). Genomes of TG rickettsiae have decayed Genomes of TG rickettsiae have decayed fasterfaster than SFG rickettsiaethan SFG rickettsiae

ConclusionsConclusionsLoss of genes for sugar metabolism, lipid Loss of genes for sugar metabolism, lipid biosynthesis, nucleotide synthesis, and biosynthesis, nucleotide synthesis, and amino acid synthesis may explain failure amino acid synthesis may explain failure of cultivationof cultivationStrong genetic similarities of the genomes Strong genetic similarities of the genomes suggest that our seemingly endless suggest that our seemingly endless creation of new species should terminatecreation of new species should terminate

Rickettsial Genes Effecting PathogenesisRickettsial Genes Effecting PathogenesisAdhesins: Adhesins: ompAompA, , ompBompBPhagosomal escape: Phagosomal escape: pldpld, , tlyCtlyCActinActin--based mobility: based mobility: rickArickAOther potential membranolytic activity: Other potential membranolytic activity: tlyAtlyA, pat, pat--11AutotransportersAutotransporters: OmpA, : OmpA, OmpBOmpB and and ScaSca proteinsproteinsType IV secretion system: Type IV secretion system: virB/virDvirB/virD genesgenesinvAinvA and others suchand others such sodBsodB and and IpxLIpxL

Rickettsial Propulsion by Host FRickettsial Propulsion by Host F--actinactin

Rickettsia conoriiRickettsia conorii Infection of MicrocirculationInfection of Microcirculation

Pathogenic Mechanisms of Cell and Tissue Injury in Rocky Mountain Spotted Fever

Production of reactive oxygen species by Production of reactive oxygen species by rickettsiarickettsia--infected endothelial cells infected endothelial cells →→oxidative stressoxidative stressHost factors: older age, Host factors: older age, glucoseglucose--66--phosphate phosphate dehydrogenasedehydrogenase deficiencydeficiency(? oxidative stress(? oxidative stress--inducedinducedhemolysishemolysis), ), sulfonanidesulfonanidetreatment (? oxidative stress),treatment (? oxidative stress),diabetes, male genderdiabetes, male gender

Cerebral Perivascular Edema in Cerebral Perivascular Edema in Rickettsial EncephalitisRickettsial Encephalitis

Rickettsial Vasculitis: the Host Defense Components

Cytokine-activated NO-dependent Rickettsial Killing by Autophagy

Phagolysosomal Rickettsial Death

Relative Susceptibility of Normal C57BL/6,Relative Susceptibility of Normal C57BL/6,IFNIFN--γγ Gene Knockout, and MHC Class I GeneGene Knockout, and MHC Class I Gene

Knockout Mice to Knockout Mice to Rickettsia australisRickettsia australis

0.50.5MHC MHC –– I KOI KO3131PerforinPerforin KOKO1.95 x 101.95 x 1022IFNIFN-- γ γ KOKO

3.6 x 103.6 x 1044WildWild--type C57BL/6type C57BL/6

LDLD5050Mouse strainMouse strain

Differential Diagnosis of Rickettsial Infections

Early stage: dengue, typhoid fever, malaria, drug reaction, hepatitis, secondary syphilis, measles, rubella, enteroviral and other arboviral infections

Severe stage: meningococcemia, staphylococcal bacteremia, toxic shock syndrome, leptospirosis, viral hemorrhagic fever, thrombotic thrombocytopenic purpura

Differential Diagnosis of Rickettsial Infections

Prominent gastrointestinal symptoms:viral or bacterial enterocolitis, acute surgical abdomen

Prominent neurologic signs: viral or bacterial meningoencephalitis

Prominent pulmonary signs: pneumonia, ARDS

Why Rickettsial Diseases Are Neglected and Seldom DiagnosedDiagnostic assays are rarely available in the tropicsDiagnostic assays are rarely available in the tropicsSingle sample acute serologic diagnosis is Single sample acute serologic diagnosis is insensitiveinsensitiveLack of epidemiologic data (incidence, geographic Lack of epidemiologic data (incidence, geographic distribution, seasonality) in most tropical locations distribution, seasonality) in most tropical locations bury rickettsioses among malaria, typhoid, acute bury rickettsioses among malaria, typhoid, acute viral syndrome, FUO considerationsviral syndrome, FUO considerationsPaucity of clinical studies that address rickettsioses Paucity of clinical studies that address rickettsioses in tropicsin tropics

Opportunities

Absence of established centers of excellence for Absence of established centers of excellence for the study of rickettsioses in the tropics.the study of rickettsioses in the tropics.Growing cadre of well trained Growing cadre of well trained rickettsiologistsrickettsiologistsin South America and Africa.in South America and Africa.Regions with sufficiently high incidence to Regions with sufficiently high incidence to investigate prospectively mechanisms of investigate prospectively mechanisms of human immunity, host risk factors for severity human immunity, host risk factors for severity of illness, basic science of diverse interesting of illness, basic science of diverse interesting rickettsial strains, and vector biologyrickettsial strains, and vector biology