fournal of the American Mosquito Control Association, lO(4):589-592, 1994 Copyriehi @ 1994 by the American Mosquito Control Association, Inc'

SOURCE AND SPREAD OF AEDES ALBOPICTU,S IN THE REGION OF

GIAN LUIGI DALLA POZZA,| ROBERTO ROMI' exp CARLO SEVERINI'

ABSTRACT. Colonies of Aedesalbopictw were discoveredat the end of the summer of 1991 in the Veneto region of ltaly. To locate the source ofthe infestation, a detailed investigation was carried out a-otrg "oitpuoies deiling in the production ofrecapped tires. Becausemost ofthe tires had been imported from ihe USA, it was surmised that this could have been one sourceof the infestation. This hypothesis wasconfirmed in the summer of 1992following an inspectionof a load of usedtires from Atlanta, Georgia, in which le. albopictuseggswere found. Despitecontrol measuresin 1991,many coloniesofle. albopictus are now well established in large areas of the region. Adults are active between the months of April and October. They are very susceptibleto the most common insecticides.

In September 1991, the first breeding site of In the 2nd week ofJuly, a container of400 used Aedesalbopiclus (Skuse) in the Veneto region of airplane tires from Atlanta arrived at one ofthe Italy was recorded (Dalla PozzaandMajoi 1992). company's sitesin Maserd, was processedthrough This site, in the commune of Maseri, Province customs,and then opened.Prior to shipment to of Padua, consistedof a tire storagearea owned Maseri, the load had beentransported in a sealed by a company that recaps used airplane tires im- container, unloaded in the port of Livorno (a ported from the USA. By the end of fall 1991, town freefrom infestation of,4e. albopictus\,and,, the infested area was restricted to a neighboring still sealed,went by truck to Maseri, where it territory (Albignasego),where some breeding sites was opened in accordancewith normal proce- were discovered in a wide variety of containers dure. Thus any mosquitoes found in the load in private dwellings and in a licensedcar dump. could not have originated from any area other Becauseused tires are known to be the principal than that of departure. About 50Voof the load means of dispersal of le. albopictus (Hawley et were tires that had already been recapped (bear- al. 1987, Craven et al. 1988),it was suggested ing the manufacturedates 1978, 198 l, and 1985) that the source ofinfestation was the used tires and cleanedand were free from residuesleft by imported from the southern USA, where colo- any deposit of water. In l0 of the tire casings nies ofle. albopictushave been establishedfor constituting the other 500/oof the load, water several years (Moore et al. 1988, Francy et al. stains were noted. Each of these l0 was filled 1990). Two approacheswere employed to de- with 5 liters of water, then rolled for a consid- termine if the above hypothesis was true: a) a erable period of time to completely cover the direct check of the first available shipment of interior surface, after which they were leaned used tires imported from abroad to the compa- againstan outdoor wall. Finally, all l0 tires were ny's works in Maseri; b) an investigation, to be covered with a plastic sheet.After 4 days, lst- carried out in wintertime. to discover other im- stagelarvae of Ae. albopictuswere discoveredin porters active in the region and to pinpoint their 4 ofthe l0 tires. In all. 380 larvae were counted import and salesmarkets. Some breeding sites and left inside the tires to develop to the pupal were also kept under observation to establishthe stage,then they were collected and taken to a seasonalactivity of Ae. albopictzs. In addition, laboratory where they were reared to adults. The the geographicspread of the specieswas moni- cycle was completed in 14 days, and the mor- tored. tality rate was about 8o/0.The month of July 1992 We located 3 large importers with storageareas was subjectto the following climatic conditions: and recappingplants throughout the Veneto re- averagemaximum temperature 28.6C, average gion. These 3 companiesshare the same import minimum temperature18.6"C, RH 70.6010. sources,accounting for more than 900/oof the Field observationson seasonalactivity of Ae. imported materials, These sourcesare: Kansas albopictuspopulations have beencarried out since City, Kansas; Richmond, Virginia; Union City, 1991. Fourth-instar larvae were recorded until California; and Atlanta, Georgia. the end of October. At this latitude (43"23'N), During 1992, only one load of used tires was the month of October is characterizedby rela- imported into the Veneto region from the USA. tively mild climatic conditions: average mini- mum and maximum temperaturesl0 and 17"C, respectively;average rainfall 165 mm; length of photoperiod 12 h 2 min (civil twilight). In No- ' DPM, Via del Rondone l, 40122 Bologna, Italy. vember the averageminimum temperature falls 2 Department of Parasitology, Istituto Superiore di dramatically (about 4'C, with temperature oc- Sanita, Viale Regina Elena 299, 0016l Rome, Italy. casionally falling to -3oC). The hibernating eggs 589 590 JounNar or rns AMTRTcANMosquno CoNrx.ol Assocr ^TroN Vor. 10,No.4

Table l. Susceptibility of Aedesalbopictus data for the Padua population of Ae. albopictus larvae and adults to some insecticides: are shown in Tables 1 and2, respectively.These diagnostic dosagesfor the Padua population. tests showeda generalsituation of susceptibility Diagnostic dosagesare those proposed by the to all the products tested. I-arvae of the tested W"rnH"iltn Otg""tt "t* A"drt "rgyptL population are fully susceptible to diagnostic o/o dosagesof temephos and chlorpyrifos proposed by the WHO for Ae. aegypti (Linn.) (World Health Time or mor- Organization 1980).Values of LC* are perfectly Insecticide dosage tality comparable with those reported by Wesson for Adults (30 testedat each dosage) other susceptible Ae. albopictus populations DDT 4olo hour 100 (Wesson 1990). Full susceptibility to Vectobac Deltamethrin 0.025o/o hour 100 also was shown by the larvae of the same pop- Permethrin0.250lo hour 90 ulation (LCgs: 0.70 ppm) when compared with Permethrin 0.25olo 2 hours 100 those of the Aedesaegyptl referencestrain of the Propoxur 0. l o/o 2 hours 100 Istituto Superiore di Saniti (LCnn: 1.50 ppm). Adult mosquitoes of the Padua population (60 l-arvae tested at each dosage) showed full susceptibility to the diagnostic dos- Temephos 0.02ppm 100 agesand times of exposure of the tested insec- Chlorpyrifos 0.01ppm 100 ticides, with the exceptionof permethrin. In fact, adult Ae. albopictus exposed to this insecticide (0.25o/o)for I h show€da relatively low survival can survive a period of intense and prolonged (100/o)but had l00o/omortality before 2 h of ex- cold. BetweenDecember and January, the min- posure to the same diagnostic concentration. imum temperature aver€ged -2oC and occa- The current distribution of Ae. albopictus in sionally dropped as low as -7.5'C. First-instar Veneto is shown in Fig. 1. During the spring of larvae were present in late April or early May. 1992, tbe speciesbegan to spread from Albig- The hatching of eggs took place under typical nasegoto the neighboring territory ofPadua, es- climatic conditions: averageminimum and max- tablishing colonies in street drains and in peri- imum temperatures l0 and l8oC, respectively; domesticcontainers. In the summer of 1992,Ae. averagerainfall 90 mm, length of photoperiod albopictuscolonized the city of Padua, moving 13 h 30 min. These populations behaved like to the north consistent with the prevailing sea- others of the samespecies living in areasof tem- sonalwind. The distribution of coloniesover the perateclimate, as documentedby Hawley (1988). region is patchy, particularly afecting areaswith During the summer of 1992, following the low-lying vegetationand hedges.The first larvae methodsrecommended by the World Health Or- in the northern quarters of the city were discov- ganization(WHO) (1981a, 1981b),a seriesof ered at the end of August, showing that in 3 insecticidesusceptibility testswas carried out on months Ae. albopictu^shad spread over an area both adults and larvae. The results of exposure of about 4 km. During the summer of 1993,about 2/: to diagnostic dosagesor times and the baseline of the Padua city area was infested. A few

Table 2. Susceptibility of Aedesalbopictus larvae and adults to some insecticides:baseline data of the Padua population. Lethal concentration (LC) is expressedin ppm, lethal time (LT) in mrnutes. Susceptibility Insecticide (950/oconfidence limits) Chi-square Slope [,arvae LCro LCtn Temephos 0.0026 o.oo77 J.JJ l.59 (0.0023-0.002e) (0.0057-o.010) Chlorpyrifos 0.0010 0.003 6.58 1.66 (0.00088-0.ooll) (0.0023-0.0048) Vectobact 0.196 0.705 2.22 t.73 (0.1684.228) (0.486-1.023) Adults LTro LTnn Permethrin 0.250lo 29.s5 79.12 0.84 t.52 (25.47-34.28) (55.84-l12.08) : | ; Baciilus thuingiensis H- I 4 flowable concentrate (susceptibility of the Aedes aegypti rcference strain from ISS: LCro O.27 ' LCr": 1'595r. DscBMBrn 1994 OpBurrorer- exp ScrENrrrrc Norss 591

l l verueza

AREAINFESTED BY AEDES ALBOPICTUS

Fig. l. Distribution of Aedesalbopictrc in the Veneto region ofltaly hundred breeding sites, mostly in street drains, paniesdealing in the production and treading of have been recorded and regularly treated. In- recapped tires imported from the previously spections of 12 tire storage facilities in other mentioned USA locations. Despite timely im- provinces of the Veneto region yielded 5 that plementation of control measures during the were positive for Ae. albopictus.These tire stor- summersof 1992 and 1993,the infestationspread age areas are located in Portogruaro (), into the neighboring city areas, whereAe. albo- Oderzo, , (), and pictus has colonized street drains and a varietv Breganze(Vicenza) and are owned by 2 com- of artificial containers. s92 Joumrel or rrtn Arr,rpnrcat Mosqurro CoNrnor AssocrtrroN Vor. 10,No.4

In conclusion,we can reasonablystate that the Importation of Aedes albopictus and other exotic used tire trading from the USA has been the mosquito speciesinto the United Statesin usedtires means by which le. albopictus was introduced from Asia. J. Am. Mosq. Control Assoc.4:138-142. into the Veneto region. Atlanta, Georgia, is cer- DallaPozza, G. and J. Majori. 1992. First record of Aedesalbopictus establishment in Italy. Am. Mosq. tainly one of the sourcesof the infestation be- J. Control Assoc.8:l-3. load causea of used tires coming from that city Francy, D. B., C. G. Moore and D. A. Eliason. 1990. was found infestedby Ae. albopicla.reggs able to Past, present and future of Aedes albopictus in the develop in situ. Likewise, loads of infested tires .J. Am. Mosq. Control Assoc. 6:127- could have been imported from other locations, 132. such as Kansas City or Richmond, wherc Ae. Hawley, W. A. I 988. The biology of Aedesalbopictus. albopictushas infested large areas. J. Am. Mosq. Control Assoc. 4(Suppl.):2-39. Notwithstanding the control measurestaken Hawley, W. A., P. Reiter, R. S. Copeland,C. B. Pum- since 1991,Ae. albopictushas establishedcolo- puni and G. B. Craig. 1987. Aedes albopictus in North America: probable introduction in used tires nies in many urban areas,surviving the rigors of from northernAsia. Science236:1 I lul-l I 15. winter and rapidly adapting to many placeswhere Moore, C. G., D. B. Francy, D. A. Eliason and T. P. clear water gathers temporarily. Therefore a Monath. 1988. Aedes albopictus in the United greater dispersal of the speciescan be expected States:rapid spreadofa potential diseasevector. J. in future years. Am. Mosq. Control Assoc.4:356-361. We thank Giancarlo Majori for his kind re- Wesson,D. M. 1990. Susceptibility to organophos- vision of this paper; the Meteorological Station phate insecticidesin larval Aedesalbopictus. J. Am. of the Botanical Gardens, University of Padua, Mosq. Control Assoc. 6:258-264. World Health Organization. I 980. Resistanceof vec- for the climatic valuesregarding l99l, 1992, and tors of diseaseto pesticides.W.H.O. Tech. Rep. Ser. 1993; and the mosquito control agencyAzienda 655. Municipalizzata di IgieneUrbana of Padua(AM- World Health Organization. l98la. Instructions for NIUP) for its technical support. determining the susceptibility or resistance of adult mosquitoesto insecticides.WHO/VBC 81.805. l98lb. Instructions for REFERENCESCITED World Health Organization. determining the susceptibility or resistanceof mos- Craven,R. 8., D. A. Eliason,D. B. Francy,P. Reiter, quito larvae to insecticides.WHO/VBC 81.807. E.G. Campos.W. L. Jakob,G. C.Smith. C. J.Bozzi. C.G. Moore,G. O. Maupinand T. P.Monath. 1988.