6/19/2019 I have got 45m i n … … First 15 min… •A travel medicine physician… •Evolution of epidemiology of rickettsial diseases inbrief “Epidemiology of rickettsial •Expanded knowledge of rickettsioses vs travel medicine infections” •Determinants of Current epidemiology of Rickettsialinfections •Role of returning traveller in rickettsial diseaseepidemiology Ranjan Premaratna •Current epidemiology vs travel health physician Faculty of Medicine, University ofKelaniya Next 30 min… SRILANKA •Clinical cases 1 2 Human Travel & People travel… Human activity Increased risk of Regionally and internationally contact between Bugstravel humans and bugs Deforestation Habitat fragmentation Regionally and internationally Echotourism 3 4 This man.. a returning traveler.. down Change in global epidemiology with fever.. What can this be??? • Thisisthe greatest challenge faced by an infectiousdisease / travel medicine physician • compared to a physician attending to a well streamlined management plan of a non-communicabledisease… … ... 5 6 1
6/19/2019 R ickettsial diseases • A travel medicine physician… • Represent some of the oldest and most recently recognizedinfectious • Evolution of epidemiology of rickettsial diseases inbrief diseases • Expanded knowledge of rickettsioses vs travel medicine • Determinants of Current epidemiology of Rickettsialinfections • Athens plague described during 5th century B C … … ? Epidemic typhus • Role of returning traveller in rickettsial diseaseepidemiology • Current epidemiology vs travel health physician • Clinical cases 7 8 By 1970s-1980s four endemic rickettsioses; In 1916 .......... a single agent unique to a given geography!!! • R . prowazekii was identified as the etiological agent of epidemic typhus • Rocky Mountain spotted fever • Mediterranean spotted fever • North Asian tick typhus • Queensland tick typhus Walker DH, Fishbein DB. Epidemiology of rickettsial diseases. Eur J Epidemiol 1991 9 10 Family Rickettsiaceae Transitional group between SFG and TG Genera Rickettsia • R . australis • R . akari Spotted Fever Group (SFG) • R . felis Typhus Group (TG) • (evolutionary geneticrelationships) 11 12 2
6/19/2019 Transmitted by…..ticks, mites, fleas and lice.. Genera Orientia • S FG: mainly ticks, also fleas (R . felis) , mites (R . akari) • TG : [Separated from Genera Rickettsia in1995; antigenically diversespp] R . prowazekii • Human body louse (Epidemic louse-borne typhus, recrudescenttyphus) • flying squirrel ecto parasites (Flying squirrel associatedtyphus) (Amblyomma ticks) . typhi (Murine typhus) R –Fleas • Orientia (Scrub typhus) • Larval mite (chigger) … ??Leeches • (Thomas W eitzel) 13 14 ia conorii complex (2005)….. Eg: R icketts (based on epidemiological and clinical differences) • R . conorii-conorii / Malish strain): Mediterranean spotted fever(MSF): Mediteranian andAfrica • R . conorii- Astrakhan strain: Astrakhan fever, Southern Russia Identification of rickettsial spp from pathogenicto • R . conorii-Israeli : Israeli spotted fever non-pathogenic potential across the globe... • R . conorii-Indica : Indian tick typhus: India, Sri Lanka and Pakistan • Rhipicephalus spp.ticks 15 16 Rickettsia spp.. •30 validated species, incl. 17pathogens Effect of globalwarming? •> 100 unclassified rickettsial isolates •Major humanpathogens 17 18 3
6/19/2019 Global warming linked to changing epidemiology ofMSF 2003 heat wave • Effect of on tickbehavior • ( ↑ incidence of R anguineus (Brown Dog Tick) -transmitted h. S • Fatal MSF inFrance diseases) • one man; 22 attached ticks • Multiple eschars • ↑ period of activity • 2 – 6% fatality reaching 30% in hospitalized patients • ↑ aggressiveness • ↑ biting of unusual hosts (humans) (Socolovschi et al . 2009. Parola et al. 2008) • Multiple eschars, severeforms 19 20 TBR: has become a worldwide disease Orientia tsutsugamushi (Scrubtyphus) (Parola et al. 2014) • More than 20 antigenically distinctstrains • Originally, 3 prototype strains; Gilliam, Karp and Kato • Later, additional antigenic types: Kawasaki, Kuroki, Shimokoshi etc and other distinct serotypes in the tsutsugamushitriangle • Novel orientia species being described outside the tsutsugamushi triangle; Dubai (O. chuto) and • in Chile (proved novel: “Named”, yet to be published (ThomasW eitzel) 21 22 This Antigenic heterogeneity of Orientiatsutsugamushi reason for • frequent outbreaks and reinfection • Differences in Virulence among the strains • Variation in the general course of the disease and the prognosis dependingon the endemicstrain 23 24 4
6/19/2019 T oday ........ Many Organisms / Serotypes / Strains 25 26 Historically • A travel medicine physician… • Evolution of epidemiology of rickettsial diseases inbrief • Different species of prokaryotic pathogens were defined based • Expanded knowledge of rickettsioses vs travel medicine • on the diseases theycaused • Determinants of Current epidemiology of Rickettsialinfections • regardless of other ecological or evolutionaryconsiderations • Role of returning traveller in rickettsial diseaseepidemiology • Current epidemiology vs travel health physician • Clinical cases Walker DH, Ismail N. Nature Reviews: 2008 27 28 •Novel R ickettsia isolates •Clinical manifestations of most •Vary much less from one another rickettsioses are neither specific to a •Is an overenthusiastic designation of manynew particular agent nor to a geographic species distribution Walker DH, Ismail N. Nature Reviews: 2008 Walker DH, Ismail N. Nature Reviews: 2008 29 30 5
6/19/2019 • A travel medicine physician… • Evolution of epidemiology of rickettsial diseases inbrief • R . africae and R . parkeri • Expanded knowledge of rickettsioses vs travel medicine • R . japonica and R . helongjiangiensis • Determinants of Current epidemiology of Rickettsialinfections • Role of returning traveller in rickettsial diseaseepidemiology • Current epidemiology vs travel health physician show minimal differences • Clinical cases Walker DH, Ismail N. Nature Reviews: 2008 31 32 Most prevalent rickettsiosesis Epidemiology of Tick borne Rickettsioses 1. Is based mainly on Rickettsia isolated in Ticks • Basedon • “Priority agents” forsurvaillance 2. Reporting error vs rickettsial epidemiology • Reportable rickettsial diseases • Rickettsioses which require medical attention • Rickettsioses that standout for their morbidityand mortality 33 34 “Reporting error”; RMSF in the Americas “cases” • May reflect an unrelated exposure to a vector bearing a R ickettsial agent that caused an immune response rather than the occurrence of a true rickettsiosis Most Rickettsial diseasediagnosis is based on IF A Is still the primary tool in thediagnosis Has a marked cross-reactivity within the S F G 35 36 6
6/19/2019 IFA crossreactivity… • This fact led to the change in reporting of “RMSF” cases in the United States • Low pathogenic agents may have contribute to the apparent • Now classified as “SPOTTED F E V E R Group” Rickettsioses overall increased incidence of RMSF inAmericas? 37 38 In most resource poor countries… Does this really mean… which are important for TravelMedicine… • “In your clinical practice.. you do not want to know what the organism • Rickettsial disease diagnosis is mainly on History and examination… is..??” • Ix facilities are not widelyavailable • Evenif available, its mainly serology based; “will not identify” the causative • But simply know that the illness is one ofRickettsial ?? organism.. Will end up with an umbrella term“SFG” 39 40 Perspective of apragmatist “The laboratory diagnosisof rickettsiosescan appear an academic exercise: Is it really necessary to identify thecausative agent For each of > 25 ecologically , epidemiologically , and aetiologically in a returning traveler? distinct disease comprising ‘the rickettsioses’ responds to thesafe, inexpensive, widely distributed, and highly effectiveantibiotic doxycycline” Paddock CD 41 42 7
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