Vectors vs Humans in Australia

109 Pages·2013·8.68 MB·English

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Volume 23, No. 1 JUNE 1998
JVE 23( 1): 1- 105 ISSN 1081- 1710
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Volume 23- Number 1 June 1998
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SOCIETY FOR VECTOR ECOLOGY
1998 BOARD OF DIRECTORS
OFFICERS
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SOVE Journal Editor Marc J. Klowden
JOURNAL OF VECTOR ECOLOGY
Volume 23 JUNE, 1998 Number 1
CONTENTS
Board ofDirectors ii
Guidelines forContributors
iv
Proceedings
Second International Congress ofVector Ecology, Orlando, Florida, 19-24 October 1997
Vectors vs. Humans in Australia- Who is on Top Down Under? An Update on Vector-Borne
Disease and Research on Vectors in Australia Richard C. Russell 1
Social and Cultural Responses to Emerging Vector-borne Diseases PeterWinch 47
An Overview ofRemote Sensing and GIS for Surveillance of Mosquito Vector Habitats
and RiskAssessment
P. E. R. Dale, S. A. Ritchie, B. M. Territo, C. D. Morris, A. Muhar, and B. H. Kay 54
Field Efficacy of a New Repellent, KBR 3023, against Aedes albopictus ( SKUSE) and
Culex quinquefasciatus (SAY) in a Tropical Environment H. H. Yap,
K. Jahangir, A. S. C. Chong, C. R. Adanan, N. L. Chong, Y. A. Malik, and B. Rohaizat 62
Submitted Papers
Field Evaluation of Cyfluthrin and Malathion 96 TG ULV Spraying atHigh-Rise Flats on
Dengue Vectors in Malaysia S. Sulaiman, Z. A.
Pawanchee, H. F. Othman, J. Jamal, A. Wahab, A. R. Sohadi, A.R.A. Rahman, and A. Pandak 69
Characterization and Detection of Anopheles vestitipennis and Anopheles punctimacula
Diptera: Culicidae) Larval Habitats in Belize with Field Survey and SPOT Satellite Imagery
E. Rejmankova, K.O. Pope, D. R. Roberts, M. G. Lege, R. Andre, J. Greico, and Y. Alonzo 74
Distribution, Abundance, and Seasonal Activities of Ticks Collected from Rodents and
Vegetation in South Carolina
K. L. Clark, J. H. Oliver, Jr., D. B. McKechnie, and D. C. Williams 89
JOURNAL OF VECTOR ECOLOGY
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JournalofVectorEcology 23(1): 1- 46
Vectors vs. Humans inAustralia - Who is on Top Down Under?
An Update on Vector-Borne Disease and Research on Vectors in Australia'
Richard C. Russell
KEYNOTE ADDRESS'
PreparedforPresentation atthe 2ndInternational Congress
ofVectorEcology, Orlando FL October20, 1997
DepartmentofMedicalEntomology, UniversityofSydney andICPMR,
WestmeadHospital, Westmead, NSW2145,Australia
Received18 February 1998; Accepted 18 February 1998
ABSTRACT: Australia has a diversity of vectors and vector-borne human diseases. Mosquito-borne
arboviruses are of greatest concern, but there are issues with other vector and pathogen systems.
Mosquitoes wereresponsible formorethan 35,000cases ofRossRivervirus during 1991- 1997. Barmah
Forestvirusisincreasingnationwide,andunidentifiedbunyavirusessuspectedofcausingillnesshavebeen
isolated.CasesofMurrayValleyencephalitis haveoccurredin 14ofthepast20yearsinnorthernAustralia.
Dengue is acontinuing problem fornorthern Queensland, with various serotypes being active. Japanese
encephalitishasappearedinthe Tones StraitIslands andthreatensmainlandAustralia.Althoughmalaria
iseradicated, almost 1,000casesareimported annually andoccasional casesoflocaltransmission occur.
With ticks, paralysis in children occurs annually in eastern Australia. Tick typhus (Queensland Tick
Typhus- Rickettsiaaustralis) occurs down theeastcoast, and( Flinders IslandSpottedFever- Rickettsia
honei) in Bass Strait andprobably Tasmania. Lyme disease is reported but its presence is controversial.
Fleaswereresponsibleforarecentoutbreakofmurinetyphus(Rickettsiatyphi)inWesternAustralia.Mites
cause scrub typhus (Orientia tsutsugamushi), and there was arecent fatality in the Northern Territory.
Overall, resources for investigation and control of vector-borne disease have generally been meager.
However,variousavenuesofbasicandappliedresearchhavebeenpursued,andhaveincludedinvestigations
intomosquitoecology,vectorcompetence,diseaseepidemiology,andvectorcontrol.Diseasesurveillance
programs vary between states, and mosquitocontrol programs are organized and effective in only afew
regions.There areconcerns for import ofvectors such asAedesalbopictus andexport ofpathogens such
asRossRivervirus; theformerhasoccurredbutthespecieshasnotbecomeestablished, andthelatterhas
occurred andhas resulted in amajor outbreak in the South Pacific. The predicted scenarios ofincreased
temperature and rainfall with global warming are also causing concern for increases in vector-borne
diseases, particularly the endemic arboviruses. Interestby health authoritiesis gravitating more towards
epidemiologicalreportingand less towardspublic health action. Inmany respects, humanshave much to
do to get `on top' ofvectors and theirpathogens `down under' in Australia.
KeywordIndex: Vectors, vector-borne disease, mosquitoes, ticks, mites, arboviruses.
INTRODUCTION borne disease epidemiology in Australia.
Australiahasaninterestingandhistoricassociation
This isnotintendedto beacomprehensive review with arthropods and vector-borne disease, and has
ofthevectors,pathogens,diseases,research,andcontrol contributedsignificantlytoresearchintheinternational
programs,andotherworkrelatedtovectorsinAustralia. context.Waterhouse( 1971) discussedtheearlyhistory
The objective was to provide an update, from the of Australian general entomology, including the
interaction of the aboriginal peoples and insects, and
perspective of a vector ecologist, of some relatively
recent happenings and findings pertinent to vector- citedrecordsofearlyexplorerswhocommentedonthe
2 Journal ofVectorEcology June, 1998
annoying, stinging, andbiting insects such asthe bush not; they also demonstrated that dengue onlyoccurred
flies, ants, and mosquitoes. With the extension of whereAe. aegyptiwas prevalent.
European settlement within Australia, there arose a With the advent of another vector-borne disease
concern for insects and disease, and reviews of early outbreak,AshburtonThompson, observedthe associa-
researchonthevariousvector-bornediseasesinAustralia tion between plague in humans and epizootics in rats
havebeenprovidedbyMackerras( 1948),Derrick(1957), in Sydney between 1900 and 1903, and at the same
Doherty ( 1978), and Lee et al. ( 1980-1989). A brief time, F. Tidswill recovered plague bacteria from
overview of the more significant international fleas fed on infected rats. The British PlagueCom-
achievements follows. missioninIndiawasledby anAustralian,C. J. Martin,
JosephBancroft,medicalpractitionerofBrisbane, who with A. W. Bacot, completed the story by
in 1876 discovered the adult worm (now known as demonstratingtheblockingoftheflea'sproventriculus
Wuchereriabancrofti)responsibleforhumanfilariasis, by the bacteria.
and stated in 1877 he suspected mosquitoes were Murine typhus ( Rickettsia typhi - formerly R.
involved in the transmission because he found mooseri) was firstdescribed in 1922 by an Australian,
microfilariaeinthestomachofmosquitoes(Aedesvigilax F. S. Hone, ageneral practitionerandchiefquarantine
Skuse]) that had fed on a patient. This discovery officerinAdelaide,SouthAustralia,asadiseasedifferent
occurredayearbeforePatrickManson,inChina,traced than epidemic typhus; this was one year before Maxcy
the early development of the filaria in the mosquito and Havens in the USA described a similar series of
Culex quinquefasciatus Say, an event that has been cases as distinct from epidemic typhus.
signaled as the birthofmedical entomology. With malaria research in Australia, there were
Later,inAustralia,T.L.Bancroft,aphysicianson criticalinvestigationsofanti-malarialdrugsduring1943-
of Joseph, traced the complete development of W. 1946, associated with World War II. Using mosquito
bancrofti in Cx. quinquefasciatus, and reported it in transmission of Plasmodium falciparum and
1898-1899. While working with Dirofilaria immitis Plasmodium vivax to produce experimental infections
during 1901- 1903, he demonstrated for the first time in army volunteers, N. H.Fairley, C. R. B. Blackburn,
thattheinfectivefilariallarvaeactuallybreakoutofthe J.Mackerras,andcolleaguesprovided,forthefirsttime,
proboscis at the tip when the vector ( Cx. quinque- accurate determinations of prepatent periods for both
fasciatus) is biting. parasites. They confirmed the existence of a cryptic
Elsewhere in the world, Ross observed human phase in the development and infection process of
malariaparasitesinAnophelesmosquitoesin 1897,and malariaparasitesinhumans,andthislaidthegroundwork
Reedandcolleaguesin 1900( followingthe suggestion forthepost-war discovery ofthepre-erythrocyticliver
of Carlos Juan Finlay de Barres in 1881 that yellow stages ofmalaria.
fever was spread by a mosquito) showed that Aedes Q' fevercouldalso bementioned inthis context.
aegyptiL.couldtransmityellowfever.Althoughyellow Thisdiseaseofabattoirworkers wasrecordedfirst,and
feverhas neverbeen recorded inAustralia,denguehas theetiologicalagentisolatedandidentified,inAustralia
been recognized in Australia formore than 120 years, duringtheyears 1935-1938.Theagent(Coxiellaburnetii)
since 1873 when cases were imported fromMauritius. has been shown tobe tick transmitted amongst native
Indigenous outbreaks were reported in northern animals,butthegreatmajorityofcasesoccurfollowing
Queensland in 1879 and 1885, and the first cases of aerosol infection duringoccupational exposure, and in
dengue haemorrhagic fever were described from a practical sense `Q' fever is not usually considered a
Australia when F.E.Harereferred to casesin Charters vector-borne disease.
Towers during an outbreak in 1897 in northern Apartfromthe` international' infections,Australia
Queensland. has indigenous vector-borne pathogens—viruses,
In1905,T.L.Bancroft,continuinghisinvestigations rickettsia,and(arguably) spirochaetesinfectinghumans,
of mosquitoes and disease, adduced circumstantial and vectors such as mosquitoes, fleas, ticks, and mites
evidence thatAe. aegypti was the vector ofdengue in transmitting such pathogens. Although not strictly a
Queensland. Later, during the 1916 dengue epidemic, vector-borne disease issue, head lice and scabies
which extended from Queensland into northern New continue to be a problem. Permethrin resistance has
SouthWales,J.B. Cleland,amicrobiologistintheNew been reported in both and there is evidence that dogs
South Wales Health Department, with Bradley and are a reservoir for human scabies infestation. Flea-
MacDonald, used transmission experiments with borne murine typhus ( Rickettsia typhi) occurs
volunteers to provebeyond doubtthatAe. aegyptiwas occasionally in various regions. Cases ofscrub typhus
an efficient vector and that Cx. quinquefasciatus was ( Orientia tsutsugamushi) occur in northern Australia,
June, 1998 JournalofVectorEcology 3
and there was a recent fatality. Ticks are still a THE ACARINES- MITES AND TICKS
problem in eastern Australia. Children are at risk of
paralysis,withoccasionalcasescommittedtoahospital MITES
for some days to weeks for recovery. The question of Scrub typhus
LymediseaseinAustraliaiscontroversial,butrickettsia The disease scrub typhus was well recognized
cause tick typhus. Ehrlichia are not known to occurin historically in coastal northern Queensland ( Derrick
Australia but the local situation has notbeen seriously 1961, Domrow andCook 1967), and although itis not
investigated(S. Graves,AustralianRickettsialReference a notifiable disease in Australia, it is still reported
Laboratory, personal communication). Babesia ` regularly' from Queensland. There were 31 infections
infectionsinhumans(e.g.BabesiabovisasinEuropeor officially reported during 1995-1997 ( M. Curran,
BabesiamicrotiasinNorthAmerica,orsimilar)arenot Commonwealth Department of Health, personal
known to occur in Australia( J. C. Walker, Westmead communication). Additionally, in the Innisfail area of
Hospital,personal communication), but therehas been north Queensland in 1996and 1997, there were 17 and
little investigation.
13cases,respectively,inarmyunitsonexercises; inthe
Mosquito-borne diseases,
particularly arboviral, latter instance, 13 of90 personnel were infected, and
areofgreatestconcern.Irrigatedagricultureisproviding those infectedhadnottaken doxycycline asprescribed
mosquitohabitatin aridareas, residential development forprotection againstleptospirosis( W.J. H.McBride,
continues in coastal estuarinehabitats,andconstructed James Cook University, personal communication).
wetlands to contain and treat wastewater are being Thecausativeorganism,Rickettsiatsutsugamushi,
established; situations leading to greater contact of is now called Orientia tsutsugamushi (Tamura et al.
vectors and humans and increasing arbovirus 1995), and the vectorin Queensland wasnotidentified
transmission. More than 35,000 confirmed cases of untilthechiggermiteLeptotrombidiumdelienseWalch
RossRiver(RR)virusinfectionswereofficiallyrecorded collectedinthenortherncoastalMossmanareain 1970/
during 1991- 1997. Barmah Forest ( BF) virus is 1971 yielded isolates of the rickettsia (Campbell and
increasing in distribution and activity, and there have Domrow 1974). Leptotrombidium delienseis theonly
been a number of significant outbreaks. Unidentified member ofthis essentially Oriental Leptotrombidium
bunyaviruses suspected ofcausingfebrile illness in the subgenus in Australia; and although it was the prime
NThave been isolated from mosquitoes and are being suspect,thiswasthefirstevidencethatitwasthevector.
characterized. Cases of Murray Valley encephalitis Rodents are vertebrate hosts, but transovarial
MVE) virus and/or Kunjin ( KUN) virus infection transmissioninthevectorsservestomakethemitesthe
have occurred in 14 of the past 20 years in northern critical reservoirhost.
Australia. Dengue ( DEN) viruses are a problem for In recent years the distribution of the disease has
northern Queensland, and Japanese encephalitis (JE) extended beyondQueensland totheNorthernTerritory
virus has appeared in the Torres Strait Islands. and Western Australia. In 1990 two cases of scrub
Additionally, although malariahasbeen eradicated, up typhus were reported from Litchfield Park in the top-
to 1, 000 cases are imported annually, numbers have endoftheNorthernTerritory(Currieetal. 1991, Currie
been increasing, and occasional cases of local et al. 1993), where it was not known despite a small
transmission occur. number of cases having been reported previously
Australiacontinues tohave problems withvector- ( Derrick 1961). Mammal surveys in Litchfield Park,
borne diseases; however, apart from the mosquito- showed a high prevalence of L. deliense, which
borne arboviruses, there is relatively little activity in previouslyhadnotbeenfoundintheNorthernTerritory
research, prevention or control, and there is much ( BellandWhelan 1993). Subsequently,humaninfection
left to be desired with respect to the mosquito/ was reported from the Kimberley region of Western
arbovirus situations. A more detailed examination of Australia( Quinlan et al. 1993). The disease is serious
the current state of the various situations will be and potentially fatal; it is known that virulence varies
presented below. Overall, there is not a lot ofopti- between strainsoftherickettsia,andtherewasafatality
mism; both academic involvement and funding for in the NT, near Darwin, in 1996( Currieet al. 1996).
vector-related research are diminishing; taxonomists Australian trials have been undertaken in the
and other researchers in government institutions are laboratory and field to test the protective value of
disappearing; interest by public health authorities is repellents and toxicants against the mites. Dibutyl
gravitatingtowardsepidemiologicalnumbercrunching phthalate and permethrin have both been shown to be
andmoresophisticatedreporting,withlesspublichealth effectiveinpersonalprotectioninthefieldwhenusedas
action. clothingtreatments(Francesetal. 1992)althoughdibutyl
June, 1998
4 Journal ofVectorEcology
totheexperiencewithNorthAmericanticks)worsening
phthalateandpermethrinwereshowntobenotastoxic of paralysis in the 24-48 hours after tick removal is
as dimethyl phthalate, diethylmethylbenzamide (= commonwithIx.holocyclus(Grattan-Smithetal. 1997).
diethyltoluamide), and benzyl benzoate in laboratory
There has been considerable work carried out on the
trials (Frances 1994). A generally lower toxicity of a
rangeoftheserepellents was foundwhentested inthe allergensandtoxinofIx.holocyclus towardsprotection
laboratoryagainstmitesinfectedwith0.tsutsugamushi ofhostsbydesensitizationorvaccination,respectively.
Theallergenshavebeenisolated,purified,andpartially
compared to non-infected mites but it was concluded characterized( Gauci etal. 1988, reviewed by Stone et
that most would be effective in the field at low
al. 1991). Thetoxin,knownas`holocyclotoxin' hasalso
concentrations, except dibutyl phthalate (Frances and
been isolated, purified, and partially characterized
Khlaimanee 1996).
described in a patent application [Aylward and Stone
1991] and by Thurn et al. 1992; see reviews by Stone
TICKS
andBinnington 1986; Stone 1988a,b;Stoneetal. 1989).
There are various concerns with both hard- and
soft-ticks, and tick-related effects in many parts of
Australia. Historically, tick-related human health Rickettsia
RickettsiaaustraliscausesQueensland ticktyphus
problems have been mostly associated with eastern
QTT).ItisnotconfinedtoQueenslandbutoccursdown
coastal regions where ticks have been responsible for (
mild to severe allergic reactions, through to life- the entire east coast from Cape York ( northern
Queensland), through New South Wales, to Wilson's
threateningparalysisfromsalivarytoxin, andinfection
Promontory( southernVictoria), andonly to the eastof
withpathogens( Lee1975). Inrecentyearstheparalysis
the Great Dividing Range, where environmental
toxin has been partially characterized, a new spotted-
fever-typerickettsialinfectionhasbeendescribed,Lyme conditionsarefavorableforthevectors(Campbelletal.
diseasehasbeenreported althoughnotconfirmed, and 1979, Dwyer et al. 1991, Sexton et al. 1991). Host
virus infections associated with seabirds have been animals are native rats andbandicoots, andthe vectors
indicated. Contemporary tick-related human health are hard ticks ofthe Ixodes genus—Ix. holocyclus, Ix.
problemsinAustraliawerediscussedrecentlybyRussell tasmaniNeumann, and Ix. cornuatus.
The clinical appearance of QTT and the other
andDoggett( 1997), andthefollowingencapsulatesand
Spotted Fever Group (SFG) rickettsial infections are
updates relevantaspects ofthatoverview.
similar: sudden onset of fever, headache and muscle
pain, a maculopapular rash, flu-like symptoms,
Toxin Related Paralysis
Theadultfemaleofthehardtick,Ixodesholocyclus tenderness ofthelymphnodes, andanescharatthesite
Neumann, is responsible for a toxicosis leading to ofthe tickbite. AlthoughAustralian SFG diseases are
paralysisinhumans,particularlychildren.Tickparalysis generally considered to be only mild to moderately
causedmorethan 20knowndeaths( 80% ofvictims in severe, there has been one fatal case reported from
NewSouthWaleswereunderfouryearsold) inthefirst Queensland ( Sexton et al. 1990). Treatment with
doxycycline usually effects recovery. A similar but
halfofthecentury, and othersmay havebeenascribed
to what is now known as poliomyelitis. There is an mildersyndrome,FlindersIslandSpottedFever(FISF),
antitoxin availableandnodeathshavebeenreportedin occursonFlindersIslandinBassStraitbetweenVictoria
recent years. However, during the past few years a on the mainland and the island State of Tasmania
number ofchildren have been admitted to capital city ( Stewart 1991, Graves et al. 1991). In 1991, a review
Sextonetal.1991) ofclinicalandepidemiologicfeatures
hospitals in eastern states with symptoms of early (
paralysis fromapartly engorged adultfemale tick; the of62casesofrickettsial SpottedFeverinAustraliawas
published, and this included QTT and 17 cases, which
syndrome is not often recognized quickly and this
exacerbates the clinical problem. Antitoxin is usually are now attributable as FISF.
administered, butoften thechildhastobedetainedfor Rickettsia australis infection is not a notifiable
disease, but cases are reported to the Commonwealth
somedaystoweeksbeforetheclinicalsituationresolves
DepartmentofHealthfromasmallnumberof`sentinel'
satisfactorily.
laboratoriesaspartofanationalsurveillancesystemfor
ThespeciesIx.holocyclusandIx.cornuatusRoberts
are known to be responsible for paralysis in humans infectiousdiseases. From 1992to 1996, 56R. australis
infections were notified, with most cases from
Pearn 1977, Sutherland 1983, Tibballs and Cooper
Queensland, as might be expected, and distributed
1986), andthereisareportofIx. hirstiHassall causing
paralysisin acat.Arecentreportdescribesclinicaland throughout the year ( M. Curran, Commonwealth
neurophysiologicalfeatures,andnotesthat( incontrast Department ofHealth, personal communication).
June, 1998 JournalofVectorEcology 5
Infections have been reported more frequently in transmission, the reptile tick Aponomma hydrosauri
the past decade than the last four. The increase in ( Denny)hasalsobeenimplicatedbyanassociationwith
notification may indicate increased incidence or one human case( Graves etal. 1993).
reporting, and possibly both. InNSW, forthree years,
1993-1996, the principal state reference laboratory Spirochaetes
recorded32positiveswith15fromSydney(D.Dickeson, Reports of Lyme disease in Australia came first
WestmeadHospital,personalcommunication). Official fromsoutheastern Australiainthe 1980s( Stewartetal.
reportsunderestimatetheincidenceofinfection;itisnot 1982, Lawrence et al. 1986, McCrossin 1986). This
uncommon in the northern beaches region ofSydney, prompted research in various areas, principally from
wheremorethan20casesayearonaverage(anotification two groups, with one contending on clinical and
rate of>40 per 100,000 population) are seen by local serologicalgroundsthataspirochaeterelatedtoBorrelia
medical practitioners (B. Hudson, Royal North Shore burgdorferi s.l. isresponsible forwidespread infection
Hospital, personal communication). in eastern Australia ( Wills and Barry 1991; Alpers
For some time the rickettsia isolated in Victoria 1992; Hudsonetal. 1994a,b), whiletheotherhasfailed
was thought to be dissimilar to R. australis from tofindconclusiveevidenceforatick-bornespirochaete
QueenslandandNewSouthWales,butthesituationhas following intensive vector investigations as well as
beenresolved.Arickettsiaisolated fromaSFGpatient clinicalandserological studies( Russell 1995b, Russell
in easternVictoriahasbeen characterizedasastrainof etal. 1994). Theformergroupclaimthatbloodfedticks
R. australis by PCR typing ofthe 17 kDaantigengene taken from domestic and stock animals have yielded
Baird and Dwyer 1993), and it appears likely that R. spirochaetes that cannot be cultured; these organisms
australisisresponsibleforallmainlandSFGinfections have been investigated with serology and PCR, and
J.Stenos,FairfieldHospital,personalcommunication). reportedasbeingrelatedtoB.burgdorferi(Wills 1995),
AlthoughQTTandFISFaresimilarclinically, the buthavenotbeenassociatedwiththeproposedAustralian
causative agentofFISFappearedtobedistinctfromR. Lyme disease syndrome. This group has also reported
australis( Bairdetal. 1992); PCRtyping ofthe 17 kDa clinicalsignsandsymptomsoftheproposedborreliosis,
antigengene,sequenceanalysisofthe 16SrRNAgene, and that antibodies to flagellin and OspA antigens to
and SDS-PAGE analysis all showed significant Europeanisolatesofspirochaetes( Borreliagariniiand
differencesbetweenthetwoorganisms(BairdandDwyer B. afzelii) were commonly detected in patient sera,
1993, Stenos and Dwyer 1993). On the basis of these although such seroreactivity toB. burgdorferi s.s. was
molecular characterizations, the rickettsia responsible uncommon( Hudson et al. 1994b).
for FISF has been tentatively named Rickettsia honei Itispossible there is an indigenous form ofLyme
Gravesetal. 1993, Bairdetal. 1996, Stenosetal. 1994, disease in Australia, probably due to infection with a
Stenos et al. 1997). There is also a similar disease in tick-borne spirochaete(s) unlikely to be Borrelia
northernandeasternTasmania(ChinandJennens 1995), burgdorferi s.s., and that current laboratory methods
anditmaybeFISFbuttheetiologicalagenthasnotbeen requiremodification toculturethecausativeorganisms
isolated. from ticks or human specimens. However, while the
QTT is associated with coastal and subcoastal tick-basedinvestigations( Russell 1995b, Russell etal.
regions. The causative agent, R. australis, was first 1994) may be criticized with respect to the use of
isolated frompatientsin 1946,butattempts toisolateit northern hemisphere techniques for culture, detection,
fromtickswereunsuccessfuluntilIx.holocyclusandIx. and identification of any possible local spirochaetes,
tasmani collected in southeast Queensland in 1971 none ofthe field collected questing ticks revealed any
yielded the rickettsia (Campbell and Domrow 1974). spirochaeteswhendissectedandexaminedbydarkfield
Ixodesholocyclusisthemostcommontickattachingto microscopy.Thisfactaloneisastrongargumentagainst
humans in the eastern coastal regions of Australia an indigenous spirochaete being widespread and
endemic forR. australis,andit attacks awiderange of common in ticks attacking humans and causing
hosts ( Roberts 1970); however, the widespread Ix. widespread infection in southeasternAustralia.
tasmanidoesnotcommonlybitehumans(Roberts1970) NospeciesoftheIxodespersulcatusSchulze/Ixodes
andmaybeinvolvedprincipallyinenzooticcycles.For ricinus Linnaeus hard tick complex, vectors in the
Gippsland, Victoria, it has been suggested that Ix. northernhemisphere,havebeenfoundinAustralia,and
cornuatus may be an important vector (Graves et al. this has clouded the issue of possible transmission of
1993). Thehosts ofFISFandthevectorsareunknown, Lymeborreliosis spirochaetes to humans in Australia.
althoughonFlinders Island, whereIx. tasmaniwas the The logical candidate vector species for an endemic
mostcommontickonhumans andmay beinvolved in zoonotic spirochaete in coastal eastern Australia is Ix.