Journal of the American Mosquito Control Association, lO(l):14-23, 1994Copyright @ 1994 by the American Mosquito Control Association, Inc.

JAPANESE AEDES ALBOPICTU,S AMONG FOUR MOSQUITOSPECIES REACHING NEW ZEALAND IN USED TIRES

MARSHALL LAIRD,' LESTER CALDER,' RICHARD C. THORNTON,3RACHEL SYME,4 PETER W. HOLDER5 ar.ro MOTOYOSHI MOGI6

ABSTRACT. Since a 1988-89 survey of northern New Traland revealed no additions to the knownmosquito fauna, this country's used tire importations have much increased. Relevant entomologicalquarantine was thus monitored in a November 1992-Jantary 1993 Auclland project, during which almostth of 8,549 casings from Japan proved wet on inspection. In this study and at 2 South Island portsafterwards, 5 vessels from Japan and one from Australia were found to have brought in mosquito-infestedused tires. Live Aedes albopictus (all larval instars, pupae, and adults) and Aedes japonicus, and deadTripteroides bambusa were discovered in shipments from Japan (3 interceptions each in the first 2 cases,and one in the 3rd). Live Tripteroides tasmaniensis were recorded from the Australian cargo. One of theAe. albopictus arrivals was followed by an apprehended introduction at an Auckland importer's premises.

INTRODUCTION

New Zealand (NZ) lacks all significant vector-borne diseases of humans, and pest mosquitoproblems are localized and quite trifling by com-parison with those of most other countries. Onlyl4 resident species of Culicidae are known, andpotential larval habitats are notably underuti-lized (Laird 1990). Three exotics, Culex (Cx.)qui nquefas c i arars Say, A ede s (F i n I ay a) no t o s c r i p -

lus (Skuse) and Aedes (Halaedes) australis (Er-ichson) were first reported here in 1848, 1920,and 1962, respectively. Ongoing surveillance, in-cluding the 1988-89 Northern Mosquito Survey(Laird 1990), has not revealed additional estab-lishments.

Lately, however, the rapidly developing inter-national trade in used tires, which has occasionedwidespread detected importations of live mos-quitoes and actual establishments in severalcountries, has caused concern that NZ might beinvaded by the cold-hardy Japanese strains ofAedes (Stegomyia) albopiclus (Skuse) (the Asiantiger mosquito) central to this problem. During1989-91, New Zealand's annual used tire im-ports (all sources) averaged slightly more than aquarter of a million but in l99l-92 jumped from

I Honorary Research Fellow, School of BiologicalSciences, University of Auckland, Private Bag, Auck-land, New Znaland.

'� Deputy Medical Officer of Health, Central Auck-land Health District Community Services (CAHDCS),Auckland Area Health Board (AAHB), Private Bag92605, Symonds Street, Auckland, New Zealand.

I Senior Health Protection Officer, CAHDCS/AAHB.a Health Assistant, CAHDCS.5 Scientist (Entomology), Ministry of Agriculture and

Fisheries (MAF) Quality Management, P. O. Box 24,Lincoln, New Zealand.

6 Chief, Division ofParasitology, Department ofMi-crobiology, Saga Medical School, Nabeshima 5-l-1,Saga 849, Japan.

260,876 to 414,486 (data from NZ Ministry ofCommerce). Up to 2l countries were involvedin the trade over this period. However, Japanwas the largest single source throughout, supply-ing an annual average of 217,267 tires (85.80/o ofthe total from all sources) in 1989-91. and391,373 (96.8o/o of the total) in l99l-92.

Quarantine responsibilities regarding importsreaching NZ by sea or air lie with the Ministryof Agriculture and Fisheries (MAD, from whichthere was hearsay evidence in 1992 that mos-quito larvae had recently been noticed duringinspections of newly unloaded wet tires at Auck-land. Because of the health implications of this,Central Auckland Health District CommunityServices/Auckland Area Health Board (CAH-DCS/AAHB) designated a team of 4 to explorethe question via a search for Culicidae in a pro-portion of the load of all containerized consign-ments of used tires reaching local importers dur-ing a project starting on November 16, 1992,and ending "soon after any discovery of mos-quitoes". This paper reports and analyzes theresults achieved.

METHODOLOGY

One of us (L.C.) handled overall organization,M.L. provided entomological advice, R.C.T. ar-ranged necessary purchasing and operational/li-aison details, and R.S. was in daily charge ofbothmonitoring and recording incoming consign-ments. Two data recording forms were devised,the first outlining each inspected container's his-tory and the 2nd detailing mosquito or otherbiological samples secured. All concerned werefamiliarized with the required collecting andpreservation procedures. The need to remainvigilant throughout every inspection was urgedin the light of the experience of Craven et al.(1988) whose infestation rate for wet and dryAsian used tires sampled at USA ports was only6.8 mosquito-positive casings per 10,000.

Mencs 1994 As. ttnoptcrus Rrecnss Nnw Zperer.rp

The agreed routine for CAHDCS/AAHB in-spection was for MAF to notify R.S. on themorning of each day when shipping containerswere to be opened and unloaded under officialscrutiny at an importer's premises. In practice,though, unloading was sometimes in progress orcompleted before she could attend. She was thusoccasionally absent when the doors were un-sealed. This had implications for the desired ran-dom selection of 100/o (ca. 7O) of tires from thedifferent sectors ofa tightly packed load.

RESULTS

Voyage data and wet/dry status of tires on re-ception: During the project 37 shipping con-tainers were monitored. One had been takenaboard at Pusan, S. Korea, and another (withtires from Stuttgart) at Rotterdam, The Neth-erlands. The remaining 35 had originated fromJapanese ports. These constituted 94.60/o of thetotal closely conforming to Japan's yearly shareof the trade for 1992. Fifty percent had beenshipped from Yokohama, l7o/o from Kobe, 10o/ofrom Nagoya , and 7o/o each from Tokyo and Moji.Except for Moji, which is in northern Kyushu onShimonoseki Strait, these cities are in southcen-tral Honshu. The port of origin was unclear forthe remaining 9ol0. Some voyages were direct,taking as little as 15 days. Others included briefcalls at intermediate ports in Japan, Pusan, HongKong, and Kelang (Moluccas, Indonesia). Theduration of the trip to Auckland thus ranged upto 22 days. Individual aboard-to-discharge timefor shipping containers averaged l8 days. Off-loading until delivery (unopened) in an Aucklandindustrial suburb took a further l-18 days (mean: 6). Forty percent were delivered within 4 days,and 28o/o in from 9 to l8 days. The lengthierperiods in wharf storage reflected the Christmas,/New Year's component of New Zealand's mainsummer holiday period. Once received by theirimporters, 660/o of the containers were emptiedof tires on the day of delivery, the rest usuallythe next day.

Although the NZ Department (now Ministry)of Health had been specifying since 1987 thatclean and dry used tires be shipped to importers,24 (64.90/o\ of the 37 monitored containers heldwet tires (the 2 from S. Korea and The Nether-lands/Germany did not). By "wet tires" we meanany exhibiting any quantity of water. Old wa-termarks were not counted because Craven et al.(1988) reported: "No eggs hatched from theflooded debris from 2,213 tires with water-marks."

Our incidence ofwet tires per container rangedfrom 2 (2.8o/o) out of 72 inspected, to 802 (88.9olo)out of902. Individual tires usually held less than

I liter of (nonsaline) water, ranging from 100 to500 ml. Of the 9,749 tires examined during theproject, 2,655 (27.2o/o) were wet. This incidencerose to 3 I . I o/o when the I ,200 non-Japanese tireswere excluded. None of the 37 containers mon-itored had structural damage permitting entry ofeither rainwater or seawater, so all arriving wettires must either have been in that state whenpacked in Japan or have acquired a trifling watercontent due to en route condensation.

Mosquitolindir?gs.' Random sampling of wettires proved negative for mosquitoes or othermacroscopic organisms until almost 2 monthsafter the project began. Then, on January 13,I 993, Culicidae (Ae. albopictus) were discoveredin and around a 20-ft. container brought to awarehouse in the Auckland suburb ofMt. Roskillon the previous day. It had been hoisted aboardthe ship Hua Yuan Kouat Nagoya on December9, 1992, after being filled with tires (possibly inTokyo where the exporter's office was located,or perhaps elsewhere) at least a day or so earlier.After calling at Yokohama next day, the vesselsailed directly to Auckland, arriving on Decem-ber 27, when the container was ofloaded. It wasnot delivered to the importer for another I 6 days,having been in transit for at least 35 days.

Although R. Syme had been notified that theHua Yuan Koz container was to be unsealed andemptied on the afternoon of January 12, 1993,she found that unloading had been completedthat morning. Eighty tires, all of them wet, werethen inspected and found negative for Culicidae.Next morning, after searching 160 more wet cas-ings, she discovered a single live 4th instar mos-quito larva in the 4, I 68th tire ofthe project. Thiswas preserved in 70olo alcohol, and with extraassistance, all wet tires examined on the previousday were searched again and the rest ofthe con-signment was inspected. Twenty-three of theload's 802 wet tires (the largest number recordedfrom any single container during the project, con-stituting 88.9olo of the 902 casings present) har-bored 46 live larvae and 6 pupae, and in oneinstance a sodden female. The number of im-matures per tire ranged from one (in 3 instances,twice a 4th instar and once a pupa) to 7 (in 2instances, the first involving 2 4th-instar larvae,2 3rds and 3 2nds; and the 2nd, one 4th-instar,three 3rds, one 2nd, one lst and a pupa). Allwere identified by M.L. as Ae. albopictus, and,examples were sent to M.M. who confirmed theidentification. From now on all wet tires wereroutinely searched.

During the reinforced search on January 13, 2or 3 unfamiliar mosquitoes were noticed in flightabout the now-empty container by a universitygraduate student, Gene Browne. He reportedthem as being black with silvery-white leg bands

M.mcx 1994 AB. At-aorrc1'vs Relcnrs NBw Zeet-nxo l 7

THIS WEEK

BUY ANY IMPORTED ASIAN USED TYRE

AND WE'LL GIVE YOU

MORE THAN YOU BARGAINED FOR!

f4

f

You can choose from any one of three dendly diseases, only this week, andonly when you buy a used Asian tyre.

Typhoid, yellow fever or dengue fever cnn be yours - FREE, and we'll eventhrow in some Ianae.

So come in and see us at nny non-Firestone tyre centre and we'll give you Ireal buzz.

Fig.2. Flier distributed by a tire company following the initial press release on imports of Aedes albopictusto Nz. Reproduced by permission of Firestone Tire and Rubber co. of NZ Ltd.. Auckland.

January 14 after a direct voyage of 16 days. Itwas delivered to an East Tamaki (South Auck-land) importer on January 21, when permethrinwas sprayed into its tightly packed mass of 1,290used tires on unsealing and opening. The doorswere closed again pending unloading next morn-ing 24 days after departure from Yokohama. R.Syme inspected 800 tires, 40 of which were wetbut lacked Culicidae. On the afternoon of Jan-uary 22, 100 more tires were examined by anMAF inspector, who discovered live lst- and3rd-instar larvae and a pupa in 500 ml of waterin the last casing. Unloading was halted imme-diately. The container was again sprayed with

permethrin and closed. As before the mosquitoesproved to be Ae. albopictus.

The E. Tamaki container was re-opened onthemorningofJanuary25, with R.S. and2 HealthProtection Officers from South Auckland HealthDistrict (SAHD)/AAHB inspecting its remainingtires. Still-living Ae. albopictus immatures wererecovered from 2 of them, truck tires each hold-ing about a liter of water, bringing the total forthe Yokohama container to 29 lawae of all in-stars and 5 pupae. Dead Culicidae were foundin 20 more tires, but samples from only 2 ofthesewere received by M.L. for identification. In one(with ca. 100 ml of water) there was a decom-

l 8 JounNer- or rnE ArrreRrcAN Moseurro Covrnor Assocnrrox

posing 4th-instar larva of Ae. albopictus. Theother (with ca. 3OO ml of water) yielded a long-dead adult female of this species. All told, 340(26.20/A of the consignment's casings were wet.

On January 27-28, a 2O0-m-radius survey ofartificial containers was undertaken around thisimporter's premises, yielding 93 water-holdingsites of which 60 (64.5o/o) were mosquito-posi-tive. The percentage of utilization was closelycomparable with 1988-89 figures. Of the 37 sam-ples taken from tires, large outdoor accumula-tions of which were adjacent to the East Tamakiwarehouse, a number of those received by M.L.held immatures from more than one tire. The23 occupied artificial containers other than tiresinspected (oil drums, plastic buckets, industrialscrap ofvarious kinds, an upturned canoe, etc.)showed 7 lo/o tttilization by Cx. pervigilans, 5oo/oby Ae. notoscriptus, and 25o/oby both. The 37*positive tires showed 68-70/o utllization by thelatter, 62.50/o by the former, and 31.30lo by both.They also revealed 2 triple utilizations in rejectedtires earlier imported from Japan. The 3rd spe-cies present was Ae. albopictus.

One sample provided 35 3rd- and 4th-instarlawae of Ae. notoscriptus, 13 2nd to 4th instarsof Cx. pervigilans, and a 2nd-instar I e. albopic-tus. The other held 4l Ae. notoscriptus larvae otall instars, 3 3rd and 4th instars of Cx. pervigi-lans, and 2 3rd instars of Ae. albopictus. Again,identifications and instar status of the last-men-tioned species were confirmed by M.M.? Bothsamples also included pupae of the 2 residentmosquitoes, which have oviposition-to-adult in-tervals in excess of 2 wk under optimum con-ditions (Graham 1929;M.L. unpublished data).The presence of these pupae proves that the 2source tires had been discarded since at leastJanuary 13-14, and had therefore been there fora week or more prior to the arrival of the Ae.a I bop ict us -infested container.

In consultation with Ministry of Health andMAF Border Services a 5OO-m-radius larvicidingand artificial container destruction operation wasnow implemented. It was centered upon the pointwhere the infested shipment had been unpacked.The rationale included the rather slow dispersal

7 Whose returned material has been lodged in theinsect repository of Landcare Research NZ Ltd., Mt.Albert Research Centre (formerly Entomology Divi-sion, NZ Department of Scientific and Industrial Re-search), Auckland. These reference collections now alsohouse the other mosquito specimens secured duringour project, plus sets ofall larval instars and pupae, ofAedes albopictw reared for the purpose by M.M. from2 strains derived from Seburi, in inland NW Kyushu'and Kabeshima, offshore from northern Saga Prefec-ture, Kyushu.

time for Ae. albopictus already considered in theMt. Roskill operation. Also, most of the extend-ed treatment area was open, grassed, and withoutclumps of shrubs or trees, which fit well with theevidence of Mori (1979) that a Japanese cold-hardy strain ofthis species clearly prefers to shel-ter in vegetation at intervals along a dispersalroute; helping to account for a l6-day dispersalof both sexes to only about 200 m. Fortunately,few artificial containers were present.

On January 27 a container from the st,ip God-wit was being unpacked in the Auckland suburbof Penrose when a live 4th-instar larva was pi-petted from ca. 2OO ml of water in I of 404 wettires (80. I o/o of this 20-ft. container load of 504).It was subsequently identified by M.M. as Aedes(Finlaya) japonicus (Theobald). The voyage hadoriginated at Kobe on December 28 and afterbrief calls at Moji, Pusan, Kelang, and HongKong, Auckland was reached on January I 8. Thecontainer was not delivered to its importer for afurther 8 days, and another day elapsed beforeit was opened and unloaded. On top of this over-all total of 30 days an unknown length of timemust be allowed for surface transport within Ja-pan. Inquiries via NZ Customs revealed that theexporter's address was in Osaka. In southernHonshu, Nakata ( I 962) found that in the vicinityof Kyoto larvae of Ae. japonicus occur even inthe coldest month, January.

The Godwit had continued her voyage south-ward on the day of arrival at Auckland. Havingalerted the Canterbury Area Health Board(CAHB) to the interception of le. albopictus in

tires from the Tai Ping Kou after she had pro-

ceeded to Lyttelton (the port ofChristchurch, onthe east coast of NZ's South Island), the Ministryof Health now conveyed similar advice on theGodwit.

On January 29 P.W.H. informedM.L. thatlivelate-instar larvae tentatively identified as Ae- al-bopictus had been found in a tire from the God-wil, which had berthed at Lyttelton a week ear-lier. The container had not been delivered to its

importer and opened for another 6 days, its tiresthen having been in total darkness for ca. 30

days. The identity of these live larvae was con-firmed by M.L. and M.M. as was that of 2 dead

ones of Tripteroides (Tp.) bambwa Yamada from

a tire in a 2nd container from the same source.Both containers had been uplifted at Moji. Beingbased near Moji, M.M. proceeded to investigatethe Japanese aspect of this transaction, findingthat the tires had been packed by an exporter intr(itakyushu, a large industrial city close to Moji.

This exporter sometimes arranged such exports

on learning of the availability of stocks of used

casings suitable for sale abroad. He indicated that

the tires had originated from the immediate vi-

Mancs 1994 Az. ,*aoptcrus RElcnrs Nsw ZEALAND 1 9

cinity of Kitakyushu, volunteering that the NZpurchaser had specified dry tires and that it washis custom to remove water by vacuum pump-ing. This practice could account for the presenceof small residual quantities of water in exportedused casings.

The CAHDCS/AAHB monitoring project hadceased on January 29. Two days later MAF be-gan to subject l00o/o of imported used tires toinspection. On February 15 P.W.H. contactedM.L. on the 2nd South Island finding of relevantimports in a 40-ft. container with about 1,300tires, nearly all of them wet and holding an es-timated total of ca.350 liters of water. They hadjust reached Lyttelton aboard the WellingtonMaru.lltrnerous larvae had been seen, but only2 late instars were received for identification byM.L. and M.M. They proved tobe Ae. japonicus,and as in the first instance the exporter's addresswas in Osaka.

On March l0 there was a further interceptionat Lyttelton. It involved not Japan but Australia,and a >3-m tire for an earth-moving vehicle.Two such tires from an exporter at Bayswater onthe outskirts of Melbourne, Victoria, had beenbrought from that port in 5Vz days aboard theCanterbury Express. MAF personnel found thateach held ca. 8 liters of water. The positive onecontained ca. 100 live larvae, 4th instars fromwhich were identified by M.L. as the very dis-tinctive Tripteroides (Polylepidomyia'| tas mani-ensli (Strickland), one of 3 members of its genusknown from the state ofVictoria (Dobrotworsky1965). The determination was subsequently con-firmed by Richard C. Russell, University of Syd-ney and Westmead Hospital, New South Wales,Australia.

Finally, 2 of 5 used tires employed as pack-aging on the tray of a light truck aboardthe Azal-ea Ace proved positive for Culicidae on her Au-gust 30 arrival at Dunedin, an east coast port350 km south oflyttelton. Each tire and 2 othersheld ca. I liter of water, the 5th being dry. P. W.Holder was sent 3 live larvae from one of thetires. Sixteen more were counted in the other butwere not collected when all tires were drainedand treated with permethrin. The specimens (24th instars and one 3rd) were duly identified byM.L. and M.M. as Ae. japonicus. The voyage hadoriginated from Yokohama on August 7, andafter uplifting the truck at Nagoya 2 days laterthe ship had called at 2 Honshu ports (Sakai andKobe) and 3 NZ ones (Auckland, Wellington,and Lyttelton) en route to Dunedin.

DISCUSSION

It is intriguing that some 43olo of the tires in-spected at Auckland were found negative for

mosquitoes in the first 8 wk of the monitoringproject, but the remaining 2t/z wk produced in-terceptions of Ae. albopictus (twice) and Ae. ia-ponicus (once) in consignments shipped from 2areas of Honshu and one of Kyushu in midwin-ter. Sharpened alertness from the first discoveryonwards was undoubtedly a factor, as it musthave been in the ensuing South Island intercep-tions, when MAF Border Services personnel, atter years ofrandom inspections oftires arrivingin NZ without a single confirmed mosquito iden-tification, contributed another finding of Ae. al-bopictus and 2 more of Ae. iaponicus besides afirst discovery each of Tp. bambusa from Japanand Tp. tasmaniensis from Australia! It can onlybe wondered how long such importations hadbeen proceeding unrecognized.

Signifrcance of mosquito importations to NZvia the used tire trade: Cold-hardy,4 e. albopictusand Ae. japoruczs, with 3 interceptions each, werethe most important of the potential mosquitoimmigrants discovered during the briefCAHDCS/AAHB monitoring project and its un-anticipated South Island aftermath. The first vec-tor's arbovirus-transmittingpropensities are wellknown (Hawley 1988, Tiger Tales 1992). In re-spect to Ae. japonicus, recent data from Hok-kaido (Takashima and Rosen 1989) demonstrateits suitability as a host for Japanese encephalitisvirus, which it can transmit efficiently to labo-ratory animals following oral infection. It canalso transmit this virus transovarially to its Filarvae, though its significance in natural cyclesand overwintering ofthe pathogen has yet to bestudied.

As to purely nuisance significance, being anaggressive biter of mammals, especially humans(Tanaka et al. 1979, Hawley 1988), the Asiantiger mosquito would certainly worsen NZ's pre-vailing pest mosquito situation ifestablished here.Tripteroides tasmaniensis is also a day-biter thatreadily attacks humans (Lee et al. 1989). Similardispersal ofboth species and, also of Ae. j aponicusto that ofthe introduced Ae. notoscriptus, wt'ict'is already entrenched in various natural contain-er-type larval habitats in NZ native forests (Laird1990), would likely be accelerated by a distinc-tively NZ use for old tire casings. For althoughreuse provides the main business for this coun-try's used tire trade, the more worn casings inimported consignments are often set aside for(sometimes immediate) dispatch to rural pur-chasers for use as weights on the plastic sheetingcovering ensilage piles (Laird I 990). A single suchpile is recognizable from afar by its scores tohundreds of tires, heavily utilized by Cx. pervi-gilans and/or Ae. notoscriptus but still offeringmuch unutilized larval habitat.

Fast sales of newly imported used casings for

20 Jounrvar or rnn ArrlEnrclw Mosqurro CoNrnol AssocranoN

this particular purpose might thus pose the spe-cial risk of injecting foreign mosquitoes (as eggs,whether diapausing or not, in dry tires?) intopotentially hazardous situations. Subsequentlyemerging females would have ready access to theblood of domestic stock, farmers, and feral an-imals, plus immediate recourse to large tire con-centrations for oviposition. Focal populations ofimported vectors and/or pests could thus be fa-cilitated in remote areas where their arrival mightescape notice. Range expansion from suchbridgeheads would be promoted by the diversityof containers, both artificial and natural (treeholes, rock holes, leafaxils, etc.) available as lar-val habitats nearby.

How do Northern Hemisphere mosquitoes sur-vive 5* wk of darkness between their midwinterand NZ midsummer, with a tropical crossing be-tween?: All Southern Hemisphere destinationsfor containerized Northern Hemisphere used tirespose any life history stages of mosquitoes withthe challenge of an equatorial transit. The firstsuch event for Australasia involving (possibly)cold-hardy Aedes albopictuswas reported by Kayet al. ( I 990). It concerned a single 4th-instar larvaofthe Asian tiger mosquito identified from a wettire taken from a damaged shipping container onOctober 3, 1988, at subtropical Brisbane(27'30'5), Australia. Taken aboard at Kobe onAugust 27, tllie container was damaged en route.This raised the possibility of its having been vul-nerable to entryby Ae. albopictus at intermediateports (Hong Kong and Manila, Philippines). Itwas thus not possible to state with certaintywhether the strain of this species was a cold-hardy or tropical one.

The next Southern Hemisphere record wasfrom Cape Town (33'56'5), South Africa. It con-cerned dead immatures of Ae. albopictus in ashipment of tires from Tokyo and January/Feb-ruary 1990 live early instar larvae ofthis speciesin winter shipments from Osaka and Kobe (theconsignment from the latter port had been intransit for at least 35 days). In May 1990 Corneland Hunt (1991) handled 2 more (2nd-instar)live Ae. albopictus larvae received in a shipmentfrom springtime Yokohama. They considered it"unlikely that the eggs would have hatched priorto arrival as the containers are usually sealed anddark inside", suggesting that "agitation ofwaterin the tires, resulting in the submergence of drynon-diapausing eggs while of loading might . . .have induced hatching". Soon afterwards, Juppand Kemp ( I 992) reported 3 findings of live mos-quito immatures in shipping containers landedat Durban, South Africa (some 4o north of CapeTown), from wintertime Yokohama and Tokyo.Adults reared included Ae. albopictus, Urano-taenia sp., and Ae. aegypti. The last-mentioned

mosquito is indigenous in South Africa but doesnot occur in Japan, which suggests ovipositionby a local mosquito following tire unloading. Asimilar explanation was suggested by Kay et al.(1990) for the presence of2 2nd-instar Cx. quin-quefasciatuslarvae in a tire from Japan that theyinspected at Brisbane.

All Culicidae intercepted at Auckland, Lyttel-ton, and Dunedin in arriving used tires had un-questionably come with the shipments in ques-tion. Most were alive on discovery, havingcompleted some (and in the case ofthe F/ua YuanKou Ae. albopictus, all) of their aquatic stages intotal darkness maintained for several weeks. How,then, did live examples of all larval instars, pu-pae, and adults of.4e. albopictus, also late instarsof Ae. japonicus, come to be present in sealedshipping containers transported on (especially)the 4 voyages from midwinter Japan to midsum-mer NZ?

Many of the tires in the mosquito-positiveconsignments had clearly been loaded wet; no-tably, 88.9olo for the Hua Yuan Kou and most ofca. l,3OO for the Wellington Maru. This agreeswith the South African experiences, with 85o/o ofthe tires in one of the northern winter consign-ments positive for Ae. albopictus on arrival atCape Town having been wet (Cornel and Huntl99l), and likewise 800/o of those in such a Dur-ban shipment (Jupp and Kemp 1992). These fig-ures suggest that the tires had been taken fromoutside storage dumps freely utilized by mos-quitoes. All but one of our leads to Japanese tireexporters failed to reveal where and how ship-ping containers were actually packed, and theliterature is uninformative in this regard. How-ever, our investigations revealed the existence ofsmall to large outdoor tire accumulations in Kyu-shu; and according to Japanese pest control per-sonnel one ofthe largest such dumps once causedserious nuisances downwind due to productionof mosquitoes from its tires. Those from Kita-kyushu included both the Asian tiger mosquitoand Tripteroides bambusa. which, with others,were collected from tires reaching the USA fromJapan (Craven et al. 1988).

The life history stages ofle. albopictus and Ae.japonicus that departed from midwinter Japanto reach NZ as live late-instar larvae (and in thefirst case pupae and adults too) must now beconsidered. Only one stage, the egg, is possiblefor the former species in southcentral Honshu,where its pupae are not found after October nor4th-instar larvae after November (Nakata 1962).Furthermore, in Kyushu northward throughoutthis mosquito's Japanese range, larvae, pupae,and adults cannot overwinter (Mori et al. I 98 I ).Only eggs do so (Sota and Mogi 1992a). It wassuggested by Mori et al. (198 l) that autumn-

Mencs 1994 Ae. AtaoprcTvs RsAcHEs Npw Zper.exo 2 l

emerging females lay diapausing eggs in nature.Sota and Mogi ( I 992b) found such le. albopictuseggs to survive longer than nondiapausing onesat low humidity.

New Zealand's 2 December departures fromHonshu and the December 29 one from Kyushu,and South Africa's 3 in that month and Januaryshow the chances oflarval or pupal uptake withused tires was virtually nil. And had any surviv-ing autumn females gone aboard, their existencewithin the shipping containers would have beenlimited to 5-7 days in the absence of nourish-ment other than water (Hien 1976). Had evenmouse blood been available, it might have beenotherwise. Aedes albopiclus females feed readilyfrom mice (Miyagi 1972). Mice are not unknownin shipping containers, even those passing throughthe tropics. For when on October l98l the first-ever such container was craned down to the newlagoon wharf of Funafuti atoll (8'30'S, 17 9' 12' E),Tuvalu, and opened, house mice emerged (LairdI 984). Its load, though, included bulk foodstuffs.Mice would surely find containerized tires far lessappealing.

Had any 4th-instar Asian tiger mosquito lar-vae still surviving in early December Honshubeen taken aboard the Hua Yuan Kou with ad-equate food available, they might perhaps havebeen able to pupate as the ship entered the trop-ics. And despite the absence of photosynthesisin a totally dark environment, wet tires storedfor even a little time in the open before beingpacked should have offered a diversity of, forexample, bacterial and colorless protistan foodfor detritus-feeding aedines (Laird 1988). Al-though tropical pupation might thus have beenfeasible, the survival ofthe rest ofthe voyage byany resultant adults would have been problem-atical. Had food been suboptimal, though, 4th-instar persistence might have extended througharrival and storage in NZ-Mori (1979) notes asmany as 58 days larval survival with suboptimalfood.

Although these suggested scenarios are loadedwith "ifs," all possibilities must be explored toexplain the presence oflive 2nd- and 3rd-instarAe. albopictus larvae in those 2 Japanese tiresdiscarded at East Tamaki prior to the Tai PingrKoz container's unsealing on January 21 . Be-cause 3 such larvae were collected from thesecasings on January 28, initial speculation rangedfrom interrupted oviposition by an earlier-ar-rived adult to autogeny. Either case would havefitted the observed larval development time,which in Ae. albopictus averages 7-10 days(Udaka 1959). Negative factors would have in-cluded the likely unavailability ofadequate spacefor aerial mating above or among tightly packed

tires, and the usually low incidence ofautogenousfemales (Mori 1979).

The likeliest solution was thus the loading inJapan of tires (whether wet or dry) containingdiapause eggs oviposited by autumn-emergingAsian tiger mosquitoes, and/or long-dried early-to mid-September nondiapausing eggs (Mori etal. 198 l). Because most Ae. albopictus eggs areoviposited a little above the water surface (asmuch as 54 mm above, but with a mean of I l.lmm; Amerasinghe and Alagoda 1984), those laidin stored tires in autumn when Japanese rainfalltends to be low (Sota and Mogi 1992a) mightremain unsubmerged until handling began atloading. From then onwards and during the voy-age, inevitable movement of any water (includ-ing that derived from condensation) in an egg-positive tire could stimulate erratic hatching ofdiapausing eggs for 30 days or longer (Mori etal. 198 l). Moreover, nondiapausing eggs hatcheasily when submerged at high temperatures, ir-respective of daylength.

The hatching of eggs in either state, spreadover much of the journey and during sometimeslengthy storage thereafter, could account for thepresence of any or all life-history stages of le.albopictus at the NZ (or other Southern Hemi-sphere) opening ofcontainers ofused tires packedunder Japanese winter conditions. It also sug-gests a more plausible explanation than autogenyfor the January 28 discovery of early instar Asiantiger mosquito larvae at East Tamaki. As regardsAe. japonicus and Tp. bambusa, the former over-winters as larvae in Japan's southwest (Kami-mura 1976); and in northern Kyushu the latterhas both eggs and 4th-instar larvae in diapausefrom early winter onwards (Mori et al. 1985).

Countermeasures to the international dispersalof mosquitoes via the used tire trade: ldeally,were the exportation of used tires to be pro-scribed internationally in other than "clean anddry" state following steam cleaning (which killseggs as well as larvae; Craven et al. 1988), therewould not be a problem. Neither would there bewere methyl bromide fumigation compulsory,either at the sealing oftire-loaded containers forexport or on their opening at arrival (the presentAustralian requirement; AQIS l99l). Since Rei-ter and Sprenger ( I 987) pleaded for "urgent dis-cussion at the international level" towards a uni-versally effective solution, the number of USAstates infested with cold-hardy Ae. albopictushasdoubled (Tiger Tales 1992). There have also beenadditional establishments in Albania (Adhamiand Murati 1987), northern Italy (Sabatini et al.1990, Dalla Pozzaand Majori 1992)and Nigeria(Savage et al. 1992), besides apprehended im-portations to Australia (Kay et al. 1990) and SouthAfrica (Cornel and Hunt 1991, Jupp and Kemp

22 JounNlr or rnp Aurp.rc.irl Moseurro CoNrnor Assocr,r^nor.r Vor. 10, No. I

1992). In the continuing absence ofrelevant in-ternational action and recognizing that the Asiantiger mosquito seems headed for a wider circum-global presence, NZ took rapid action to updatequarantine practice following the January 1993Auckland interceptions. From February I l00o/oof imported used tires became subject to inspec-tion, and pending early finalization of revisedquarantine procedures with the authorities ofoverseas exporting countries, mandatory methylbromide fumigation of such tires on entry to NZwas instituted in early September (informationfrom MAF and the Ministries of Customs andHealth).

ACKNOWLEDGMENTS

We are grateful for the cooperation of MAFthroughout this project, for the seconding ofper-sonnel from other Greater Auckland Health andCity authorities in the hurriedly organized Mt.Roskill and East Tamaki operations, and for thehelpfulness of CAHB. Valuable entomologicalcounsel was contributed by J. S. Pillai of Dun-edin, T. K. Crosbie of Landcare Research NZLtd. (see footnote 7 re Macromasllx) and R. C.Russell of Sydney, Australia, re Tp. tasmanien-srs. J. W. Donaldson (Value Tyres Ltd., Christ-church) gave useful insight into aspects of theused tire trade, and G. Martindale of Ministryof Health, Wellington, did wonders in overallcoordination throughout.

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