JounNar, oF THE AveRrclr.r Mosqulto CoNrRor, AssocrerroN Vol. 7, No. 1
LABORATORYTRANSMISSION OF JAMESTOWNCANYON AND SNOWSHOEHARE VIRUSES (BUNYAVIRIDAE:CALIFORNIA SEROGROUP)ey SEVERAL SPECTESOF MOSQUITOES1
PHILIP B. HEARD, MINGBAO ZHANG eNo PAUL R. GRIMSTAD
Laboratory for Arbouirus Researchand Surueillance,Department of BiologicalSciences, Uniuersity of Notre Dame, Notre Dame, IN 46556
ABSTRACT' The ability of 14speciesof mosquitoes to biologicallytransmit JamestownCanyon virus wastested. Four speciesnot previouslydfscribed as vectorsof that-virus transmittedto;*kii;t-i;;. Among membrane-fed mosquitoeswith disseminatedinfections, field-colleiled eeae" canaaei;F 1iJij, Aryoplglespunctipennis (l/!2), Coquillettidiaperturbans (2/14).and a laboratory strain of Ae.epactii (19/67) transmitted virus. Two specieswerelested for their ability to transmit snowshoehare virus: field-c!llected A e-prouocdns (4/20) and.Ae. abserratus--punctor(2/20i successfullytransmitted to suckiinj mice.Evidence regarding the role of thesespecies as field vectorsis'summarized.
INTRODUCTION gions of the United States,with the exception of one laboratorystrain that originated Oral transmissionof JamestownCanyon (JC) from El Salvador. virus has been describedfor B mosquito species: Aedesstimulans (Walker) (Boromisa Large field collections of 2 communrs group and Grim- members, stad 1986),Aedes prouocans (Walker) (Boromisa Ae. prouocans and Ae. abserratus- punctor,in Michigan in 1989made possible and Grayson1991) andAedes albopictus (Skuse) it to test the vector competenceof these species (Grimstad et al. 1989). There is evidenceto for a secondstrain of JC virus from suggestthat Ae. stimulans and,Ae. prouocansate Quebecwhere both mosquito speciesare found (Darsie natural vectors (Boromisaand Giimstad 1986. and Ward 1981).We also took this opportunity Boromisaand Grayson19g0). Jamestown Can- to test for snowshoehare (SSH) virus (Bunyaviri- yon virus isolations have been made from at dae:California serogroup) least 19 additionalspecies of mosquitoes(Grim- transmission by these species.Snowshoe hare virus has been isolated stad 1988,Campbell 1990) for which transmis- from numerousmosquito species, including Ae. sion data are lacking.Included among these are punctor and other members of the communis Aedesabserratus (Felt and Young)and otherAe. group (Belloncik et al. 1983, Grimstad 1988). communisgroup members that are suspectedof Oral transmissionof this virus has been dem- transmitting on the basis of high field infection onstratedin Ae. comrnunrs(De Geer) (Mcl-ean rates (Sudiaet al. 1971,Main et al. 1929,Grav- 1983).In addition, this virus is relevant to our son et al. 1983,Campbell i990). There is also ongoing studies of multiple California serogroup interest in Anophelesspecies, which may be virus infections of white-tailed deer (Odocoileus involved in early spring and late fall transmis- uirginianus),the primary vertebratehost for sion in the Midwest (DeFoliartet al. 1986). JC virus (Grimstad 1988),in the upper Midwest. In an effort to address questions of vector competencefor JC virus, we conductedtrans- mission trials with 14 species(18 geographic MATERIALS AND METHODS strains) of mosquitoes.Species were selectedon Ten species(11 geographicstrains) were col- the basis of their apparent potential as vectors lected and tested directly from the field and 4 and their availability for testing. Nine species species(7 strains) were colonized. Field-col- were from an enzootic focus of JC virus located lected mosquitoes were taken as adults from in the Lower Peninsulaof Michigan (Grimstad Coz-baitedtent traps at sites in northcentral et al. 1987).The remainingspecies/strains came Michigan and northwesternIndiana (Table 1). from northern Indiana and other enzootic re- Porter Flanch,in the Lower Peninsulaof Mich- igan, lies within an enzootic focus of JC virus (Grimstad et al. 1987, Heard et al. 1990). Snowshoehare virus is undocumentedat the 1 part Supported in by National Institutes of Health site; however, its range likely includes Michi- Grants AI-19679 and AI-07030. In conductine the gan's Lower Peninsula (Calisher 1983). research described in this report. the investigators All "Guide adhered to the for the Care and Use of Labo- snowmelt Aedesspecies were collected at Porter ratory Animals" as promulgated by the National Re- Ranch in the late spring, within days of their search Council and used facilities accredited by the emergence;others specieswere collected as in- American Association for the Accreditation of Labo- dicated in Table 1. Potato Creek and Spicer ratory Animal Care. Lake are in northern Indiana in a region where Mencu 1991 Moseurro TRarslrIssIoN oF JC AND SSH Vlnusns
Table 1. Mosquito strains used in transmission trials with Jamestown Canyon and Snowshoe Hare viruses. Laboratory Origin and generation Mosquito species Strain tested collection date tested Aedes canadensis PORTER RANCH MissaukeeCo., MI, May 1988 0t cinereus PORTER RANCH MissaukeeCo., MI, May 1988 0 excrucLans PORTER RANCH MissaukeeCo., MI, May 1988 0 fitchii PORTER RANCH MissaukeeCo., MI, May 1988 0 prouocans PORTER RANCH MissaukeeCo., MI, May 1988 0 proDocan^9 PORTER RANCH MissaukeeCo., MI, May 1989 0 intrudens PORTER RANCH MissaukeeCo., MI, May 1989 0 abserratus fpunctor PORTER RANCH MissaukeeCo., MI, May 1989 0 triseriatus VERO Indian River Co.,FL, 1977 30+ triseriatus SALADO Bexar Co.,TX, 1972 40+ triseriatus ALA Alabama,prior to 1958 75+ stirnuLans POTATO CREEK St. JosephCo., IN, June 1988 0 hendersoni U.VILLAGE St. JosephCo., IN, 1981 20+ epactius SANSAL Matapan,El Salvador,1968 40+ epactius GRAND Grand Co..Utah. 1968 40+ Anopheles punctipennis PORTER RANCH MissaukeeCo., MI, April 1988 0 punctipennis PORTER RANCH MissaukeeCo., MI, August 1988 0 quadrimaculatus SAVANNA Savanna,GA, acquired in 7971' 100+ Coquillettid.ia perturbans PORTER RANCH MissaukeeCo.. MI. June 1988 0 perturbans SPICER LAKE St. JosephCo., IN, July 1988 0 l These strains were tested as field-collected,newly emergedfemales. 2This strain was acquired as colony stock in 19?1.Atl other strains were originally obtained as field stock and maintained in the Vector Biology Laboratory from the year of collection listed until the time of use in this studv.
a high prevalenceof antibodyto JC virus occurs 19'C. Brain extracts from sick and moribund in all surveyeddeer populations (Boromisa and mice were tested for the presence of virus. Grimstad 1987). Specimenswere carried from Plaque assaysfor the detection of virus in mos- the field in ice-cooledboxes and housedat 19'C quitoes and mouse brain tissue were modified in 3.8-literplastic buckets. Additional handling from Grimstad and Haramis (1983).The Vero measureswere describedby Grimstad et al. cell cultures used for this purpose were main- (1e8e). tained in medium 199with a 10%serum supple- Laboratory-reared mosquitoes were taken ment (Seru-Max 2, Sigma Chemical Co., St. from coloniesat the University of Notre Dame Louis, MO), 2.2 g NaHCO3 per liter, 75.0 mg (Table 1). Larvae were reared according to gentamicinper liter, and 125.0mg amphotericin Grimstad et al. (1989), and adults were main- B per liter. For mosquito assays,the concentra- tained in the samemanner as wild-caughtmos- tions of antibioticswere increased 2 and 4 times, quitoes,with the exceptionthat the Aedestris- respectively.Samples were applied to Vero cell eriatus(Say) VERO strain was kept at 27"C. monolayersin 6-well plates,and replaced,after Virusesused in the trials were as follows: 1) a 1-h incubation at 37'C and 5% CO2,with an JC virus strain 800245,passage 3 in suckling overlay consisting of culture medium supple- mousebrain (SMB), was isolatedfrom a pool of mented with 0.8% gum tragacanth (Sigma Ae. stimulans males in Indiana and is horizon- ChemicalCo.). After 3-4 additional days of in- tally transmitted by that species(Boromisa and cubation, the plates were fixed and stained with Grimstad 1986);2) JC virus strain 136A3,pas- a crystal violet-formalin solution and examined sage 3 in Vero cells, passage1 in SMB, was for plaques. isolatedfrom mosquitoesin Quebec,Canada (H. Infectious blood meal (IBM) titers were de- Artsob, personalcommunication); and 3) SSH termined from observationsof cytopathic effects virus, "original" strain, was suppliedin lyophi- in Vero cellsgrown in 96-wellplates as described lized form, passage20 in SMB, from the Centers by Grimstadand Haramis (1983).Median tissue for DiseaseControl. culture infectious doses (TCIDun) were calcu- Mosquitoes were orally infected at a mem- lated using the method of Reed and Muench brane feeder and individually tested for trans- (1938).The valuesin Table 2 representan av- missionto newbornmice as describedby Grim- erage of titers taken at the beginning and end stad et al. (1989).Extrinsic incubation was at of the feedingperiod. 96 Jounrver,oF THE AnrrnrceN Mosqurro CoNrRor, AssocrATroN VoL. 7, No. 1
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() '=o 4417ZZzz Er Z Z at; SiSSi333333333333333 - i) N E. s*CJ Fi .3.3s o o ur€sssiig€€iEfft€€€€€€s€€ 6 N T6 >i 99 O b MARCH 1991 MoseulTo TRANsMISSIoNor JC eNo SSH Vtnusns o EE Chi-square(x') tests of homogeneitywith 1 o !6 d.f. were applied to the results for mosquito a o or more combinations of oo H@ ni 'ats. strains tested under 2 r$ ii NN extrinsic incu- \\ \\ a infectious blood meal titer and NS 2n 1981)' .a @vo bation period (EIP) (Sokal and Rohlf im oo @o) q : e.i"' the frequency in one or more cells was i:= When <5, a Fisher's exact test (FET) was used for the pairwise comparison.Similar analyseswere per- ^d \\mi \\ii NC{ d€ i; formed between selectedstrains. N$ RF3 dN or9 RESULTS o FXo o Table 2 summarizesthe results of the trials rs 8? c -O ci ca F with JC and SSH viruses.Jamestown Canyon r\ ii tr r.i \i \\ im virus isolate 800245 caused midgut infections 6A i* NM p€"E (MI) in 13/14 species(1?/18 strains), dissemi- .+cO @n cor N o nated infections (DI) in 11/74 species(13/18 o-: h#i' .: strains). and oral transmission in 5/14 species o F-tr (5/18strains). The JC virus isolatefrom Quebec, tested;how- r$ 'b:6d€: 13643,caused DIs in both species r$ N* each speciesac- \\ i\ a ever, only one individual from IoO) \i -.9 F $N Ni NM quired a DI and neither transmitted virus. $m r@ * in IBM titer (or in trq: Within a given strain, changes o 26- and EIP usually had no significant effect on the !tsY oP.- proportion of individuals with MI or DI or on .9oC virus. ii ss the proportion of individuals transmitting NN ii -oo Therefore. the results of most trials were pooled u.bq (Table2). Significantlyhigher proportions of DI tr6- Aedesepactius cl '7aa and transmission were noted for (Q$ oo 6.1 c{ SANSAL after IBMs of 7.2-7.5 3 3.o i Dyar and Knab Jcd rirj logroTCIDso/ml (FET, P = 0.002- ml), although midgut-escapebarriers occurred doseper ml after experirnentalinoculatjon(New- in only 36% of the August-collectedfemales. house et al. 1971). Unpublished studies (M. Transmission was demonstrated for Cq. pertur_ Zhang) indicate that SMICLDso titers of JC bonsfrom both Michigan (1/g) and Indiana (1/ virus are within 0.2-0.7lo916 in either direction 11); the proportion with DIs was significantly of the correspondingTCIDso titers. It is recog- higher in the latter (12,p strain < O.bOf); IBM nized that differences in mosquito infection titers were comparable for the 2 strains. rates can occur betweenvertebrate blood meals colonized -{_monq speciestested with JC virus, and artificial blood mealsof equaltiter. Thus, it 46% (16/35)of Ae. epactiusSANSAL transmit- is unclearwhether the effectiveIBM titers em- ted whereas100% (60/60) of thesefemales had ployed in these trials overlappedthe range of DIs. No Ae. epactius GRAND transmitted. and titers found in naturally infected wild verte- DIs occurred in only 2gVooverall, despite IBM brates. titers equal to and sometimesgreater than those Aedescanadensrs has beena sourceof JC virus usedto infect the SANSAL strain. The remain- isolatesin Maryland (LeDuc et al. 1g7b).New ing colonized strains, representingAe. triseria- York (Graysonet al. 1983)and Michigan (Heard tus,Ae de s hender s oni ( Cockerell) andAnophele s et al. 1990). In those studies, minimum field quadrimaculatusSay, were resistant to infec- infection rates (MFIR) were 1:1,131at the por- tion; only 0-t9% became infectedat the midgut, ter Ranch site in Michigan, l:27,408 in New whereas only 0-2% developed disseminated in- York and l:35,217in Maryland. Blood hosts of fections. this speciesinclude deer (Wright and DeFoliart Snowshoe hare virus was readily infectious for 1970,Boromisa and Grimstad 1986).as well as Ae. abserratus-punctor and Ae. prouocans and, bovines, horses and humans. among others was transmittedby both species:20% G/20) of (Nasciand Edman 1981).On the basisof limited prouocans the Ae. and t07o (2/20) of the Ae field isolations and low field infection rates, abserratus-puncfortransmitted. Significantly Eldridge (1990)excluded Ae. canadensjsand all proportions higher of femaleshad SSH virui nonaedinespecies from the list of mosquitospe- (FET, DIs P < 0.001) than JC virus DIs at cies possessinga significant biologicalassocia- equal,if not lower,IBM titers (Table 2). tion with JC virus. Aedes canadensls,indeed, does not appear to play a significant role in JC virus maintenance at the Porter Ranch site in DISCUSSION Michigan (Heard et al. 1990).This appearsto be due in part to the fact that it emersesat a This survey provides evidenceof Iaboratorv time when seasonalJC virus transmission to transmissionof JC virus by 4 additionalspecies: deer is usually well underway.The role of eco- Ae. canadensis,Ae. epactius,An. punctipennis Iogical/epidemiologicalfactors as predominant and Cq. perturbans. Evidence is also provided determinants of vectorial capacity is an argu- for the laboratory transmission of SSH virus by ment againstthe coevolutionofvirus and vector Ae. prouocansand Ae. abserratus-punctor.Con- and, in turn, againstthe likelihood of a signifi- clusive proof of vector status is difficult to cant role for this speciesin the maintenance achieveand cannot be claimedfor any of these cycle (Eldridge1990). speciesin light of the limitations of thesetrials Anophelespunctipennis has yielded JC virus and generallack of field data. However,in par- isolatesin New York (MFIR 1:16,975,Grayson agraphs below we summarize what is known et al. 1983) and Ohio (MFIRs of 1:36.b49in from published field studies regarding JC and statewidecollections, Berry et al. 1983; l:128 SSH viruses as it relates to the results of these and 1:733in localizedfoci, R. L. Berry in Grim- trials. stad1988). Blood host and other incidentalstud- The recordedIBM titers in thesetrials (b.0- ies in North America indicate that An. puncti- 7.6logro TCIDso/ml) were generally higher than pennis will feed on cattle, horses,humans and the levels of viremia reported for the amplifying numerousother vertebrates(Edman and Downe hostsof JC and SSH viruses.White-tailed deer 1964,Suyemoto et al. 1973,Nasci and Edman developpeak viremias of 3.4-5.0lo916 suckling 1981),although deer have not been specifically mouse intracerebral median lethal dose recorded.Although early spring seroconversions (SMICLDso)per ml after experimentalinocula- and anamnesticresponses in penned deer at the tion (Issel et al. 1972,Watts et al. 19?9).No Porter Ranch site in Michigan (Grimstad et al. other vertebrate specieshas yet been shown tr.l 1987)suggest a vector role for a nonaedinespe- have demonstrableviremia in the field (Grim- cies such as An. punctipennis(DeFoliart et al. stad 1988).Snowshoe hares (.Lepus americanus), 1986),no JC virus isolations have been made the natural vertebratehost of SSH virus (Grim- from the relatively few Anophele.scollected at stad 1988),develop peak viremias of 2.3-3.9logls this site to date (Heard et al. 1990). suckling mouse intraperitoneal median lethal Coquillettidiaperturbans has been a sourceof 99 MARCH 1991 MoseulTo TRANSMTssIoNoF JC AND SSH Vlnusps collected in JC virus in Connecticut(MFIR 1:26,666,Main been demonstratedin Ae. prouocans 1990),and is et al. 1979) and New York (MFIR t:1I7,677, New York (Boromisaand Grayson basedon the Graysonet al. 1983).No isolateshave come from believedto occur at Porter Ranch ob- this speciesin either Michigan or Indiana. Its fact that many of the 14 JC virus isolates from bloodhosts are numerous and includedeer, large tained from A e.prouocans at that site were collected domestic animals and man (Wright and De- newly emerged, nonbloodfed females deer Foliart 1970,Suyemoto et al. 1973,Nasci and befoie the fiist seroconversionsin sentinel Edman 1981, Boromisa and Grimstad 1986). (Heard et al. 1990). It is conceivablethat orally Like An. punctipennis and CuLisetainornata infectedAe. prouocansat Porter Ranch contrib- (Williston), transmission by Cq. perturbans ute to the po-olof transovarially infected individ- might explain JC virus transmission in the ab- uals and play little or no role in horizontal in- senceof AedessPecies. amDlification. a role Ieft to transovarially The failure of Ae. prouocans PORTER fecied progeny. A phenomenon of this sort RANCH to transmit either strain of JC virus would explain the discrepanciesbetween our was unexpected.Over a -yeatperiod, Ae. prou' field and laboratory studies' It may be relevant ocansyielded 14/20 JC virus isolates from the to the Ae. prouocans results that transovarial study site in Michigan (Heard et al- 1990).These transmissionin the absenceof oral transmission isolates were obtained there each year from has been demonstratedin over 30% of individ- adult Ae. prouocansfemales collected before or ually colonizedAe. albopictusfemales orally in- soon after the first seroconversionsin sentinel fectedwith La Crosse(LAC) virus (Bunyaviri- deer.Aedes prouocans is typically a large-mam- dae: California serogroup)(T. Streit, personal mal feederand is known to feedon deer(Means communication). 19?9,in referenceto the synonymizedspecies, Aedes abserratus-punctor and Ae. intrudens Ae. trichuris). Furthermore, Boromisa and Dyar representother examplesof aedinespecies Grayson (1990,1991) demonstrated the vecto- that appear to be potential vectors of JC virus, rial capacity of Ae. prouoconsin New York and but for which laboratory evidence remains in- reported a transmission rate of 50% (9/18) conclusive. Jamestown Canyon virus has been among field-collectedspecimens. In comparing isolatedfrom either Ae. absenatusot Ae.punctor the resultsfrom our trials and thoseof Boromisa in Newfoundland(Mokry et al. 1984),Connect- and Graysonwith similar EIPs (14 days) and icut (Spranceet al. 1978,Main et al' 1979),New IBM titers (5.8versus 5.6 logroTCIDso/ml), the York (Boromisaand Grayson1991) and Michi- population of Ae. prouoconsfrom New York gan (Heard et al. 1990).Deer may be used as (Boromisaand Grayson 1991)had an identical blood hosts (Wright and DeFoliart 1970).Aedes proportion of individuals with MI (FET, P : intrudenshas yieldedisolates in New York (Bo- 1.000)but a significantly higher proportion with romisa and Grayson 1990) and in northcentral DI (x', P : 0.010) relative to the Michigan Michigan (Heard et al. 1990). population.The lower extrinsicincubation tem- Earlier reports implicated Ae. stimulans as an perature in our study (19 versus 21'C) may enzooticvector in northern Indiana (seeTable account for differences in DI and/or rates of 2, KINGSBURY) (Boromisa and Grimstad transmissionas may the choiceof virus strain, 1986).This wascorroborated with the POTATO and other intrinsic factors. Mortality of the CREEK population of Ae. stimulons,collected specimensprevented us from testing beyond a from an adjoining county in Indiana. In com- 14-dayEIP, a problem also encounteredby Bo- paring the 2 populations, which were tested by romisaand Grayson(1991). different workers using different IBM titers, the Eldridge (1990)concluded that Ae. prouocans proportions of infected and transmitting females (and 4 other species)has a significantbiological werenot significantlydifferent (FET' P > 0.15). associationwith JC virus, achieved in part These populations of Ae. stimulans appear to through coevolutionof their respectiveances- have similar capabilities as laboratory vectors of tors. If the inability of the PORTER RANCH JC virus. population of Ae. prouocansto transmit JC virus The high proportions of Ae. epactiusinfected is borne-out in future trials, it would suggest and transmitting in this study are unsupported that this vector-virus association is an unpat- in the literature. No JC virus isolateshave been terned one and must be analyzedon a regional, reported from Ae. epaditts, nor has the existence if not smaller, geographicscale. Variability in of JC virus in El Salvador and Central America vector competenceamong geographicstrains is been reported. However, JC virus does exist well-known(Gubler and Rosen1976, Tesh et al. within the range of North American populations 1976,Grimstad et al. 1977,Boromisa et al. 1987). of Ae. epactius(Calisher 1983, Darsie and Ward Vertical transmissionis also evidenceof a sig- 1981).Based on limited samplesizes, there ap- nificant biologicalassociation (Eldridge 1990). pear to be dose-relatedmidgut escapebarriers Indeed. vertical transmissionof JC virus has in Ae. epactiusSANSAL and GRAND. i.,ouRNAL oF THE Autntcnn Mosquno CoNrRor,Assocre.rroN Vor,.7, No The susceptibility of Ae. triseriatus in these and, Ae. prouocans reportedly feed on small trials was consistently low; however,this species mammals,the former 2 on rabbits (Downe 1960, has beena sourceof isolates york ('Gr"u_ in New Means1968, Wright and DeFoliart 19?0).These son et al. 1983) and Ohio (Berry et al. 1977, results underscorethe parallels between SSH 1983) and is known to feed readily on deer and JC virusesdrawn by Eldridge (1gg0).Fur_ (Nasci 1982).Infection rates were also low for ther studiesare neededto confirm these findings the sibling species,Ae. hendersonl,suggesting with JC and SSH viruses and define their relt- that neither speciesis likely to be a sig*n"ificant vance in the natural virus cvcles. vector. The potential effect of lons_teim colo_ nization on the biological transmiision of vi_ ,rusesby these and other mosquito speciesmust ACKNOWLEDGMENTS be kept in mind. Grimstad ei al. (i9ZZ) noted We thank that laboratory colonization had diverse and H. Artsob and N. Karabatsos for pr,ovidingstocks (euebec unpredictable effects in trials with LAC virus of JC virus strain) and SSH virus, respectively, and Ae. triserintus. The same may be true for T. Streit for unpub- Iished data, JC virus and the colonizedspecies in this studv. R. Copeland,S. Hanson "rrd M. Sympatry for JC and LAb viruses (Calisher Niebylski for their participation in someof the transmissiontrials 1983, Grimstad 1988) is probably achievedin and M. Kern for excellent technicalassistance. part by the absenceor near absenceof shared vector species.Based on the analysisby Eldridge (1990),there are no speciesthat havea .."roi- able chanceof contributing to the maintenance REFERENCES CITED of both viruses. Our data suggest that Ae. tri- Belloncik,S., A. Aubin, A. Marie,J. Boisvert. seriatus does not R. contribute to the JC virus Gagnon,C. Th'ng, C. Trudel and H. Artsob. 1983. cycle;this speciesappears to be strictly a natural Arbovirus studiesin the Trois-Rividresarea. prov_ host of LAC virus. Aedescanadensis Las been a ince of Quebec,Canada. Mosq. News 4J:426-481. source of field isolates of both JC and LAC Berry, R. L.. B. J. Lalonde Weigert.C. H. Calisher, viruses and will transmit them in the laboratorv M. A. Parsonsand G. T. Bear. Ig77. Evidencefor et al. 1983,Boromisa and Grayson199i, transovarial transmission of JamestownCanvon vi_ .(_!erry rus in Ohio. Mosq. News Watts et al. 1973).Although Ae. canidensis ap- 37:494-496. Berry, R. L., M. A. Parsons, pears to be a secondaryvector of R. A. Restifo. E. D. LAC virus in Peterson,S. W. Gordon.M. R. Ohio (Berry et al. 1983), Reed,C. H. Calisher, there is no conclusive G. T. Bear and T. J. Halpin. 1983.California evidencethat sero- it is important in transmissionof group virus infections in Ohio: an 18-vearretro- JC virus. spectivesummary. pp.2lb-228.In: C. H. Calisher The trials with SSH virus underscorethe and W. H. Thompson (eds.),California serogroup importance of the commanrsgroup in the epi- viruses.Alan R. Liss, Inc., New York. Ny. demiology of this virus. Both Ae. prouocans ind Boromisa,R. D. and M. A. Grayson.1gg0. Incrimi- Ae. abserrattn-punctorwerc readily infected and nation of Aedesprot)ocans as a vector of Jamestown Canyon virus in capable of transmission to suckling mice. an enzootic focus of northeastern New York. J. Am. Mosq.Control Assoc. Snowshoehare virus has been isolatJd from 6:504-509. Boromisa,R. D. and M. A. Grayson.1991. Oral Aedespunctor (Kirby) in (Belloncik trans- Quebec et missionof JamestownCanyon virus by prou- al. 1983),Saskatchewan (Iverson Aedes et al. 19TB) oconsmosquitoes from northeasternNew york. J_ and Alaska (Sudiaet al. 1921,Ritter and Feltz Am. Mosq. Control Assoc.T:42-47. 1974),and from communlsgroup mosquitoesin Boromisa,R. D. and P. R. Grimstad. 1g86.Virus- Alberta, Wisconsin,Alaska (Sudiaet it. fgZf), vector-host relationships of Aedes stimulans and, Montana (Hoff et al. 1971),the Yukon Territo- Jamestown Canyon virus in a northern Indiana ries (Mcl,ean 1983) and the Northwest Terri- enzootic focus. Am. J. Trop. Med. Hyg. 35:1285- tories (Wagneret al. 1975).Vertebrate 1295. isolates Boromisa,R. D. have comefrom snowshoe and P. R. Grimstad.1982. Serocon- haresand other small version rates to Jamestown mammals (Grimstad Canyon virus among six 1988).Mclean (1983)re- populations of white-tailed deer (Odocoileus ported uirei- that blood meal titers of 0.1 mouseLDso nianuslin Indiana.J. Wildl. Dis. 23:23-33. were sufficient to infect Ae. communis and that Boromisa,R. D., K. S. Rai and P. R. Grimstad.19gT. comparably low titers enabled transmission to Variation in the vector competenceof geographic occur.Whether Ae. prouoconsand Ae. abserca- strains of Aedes albopictusfor Denzue 1 virus. J. tus-punctor are susceptibleat such low titers is Am. Mosq.Control Assoc.3:378-386. unknown. Definitive evidence Calisher, C. H. 1983. Taxonomy, classification, and for the use of geographic snowshoehares as blood distributionof Californiaserogroup bun- hosts by these species yaviruses.pp. is not available, although 1-16. In: C. H. Calisher and W. H. the isolation of SSH Thompson (eds.),California virus punctor serogroupviruses. Alan from Ae. would suggestas much R. Liss, Inc., New York, NY. for this species.Aedes punctor, Ae. absetatus Campbell,G. L. 1990.Epidemiology of California and MARCH 1991 MoseulTo TRANSMIssIoNoF JC AND SSH Vlnusrs 1972' Bunyamweraserogroup viruses in mountainousand Issel,C. J., D. O. Trainer and W. H. Thompson. and other areas of California. 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