Aedes aegypti (Linnaeus) is a human-biting mosquito and the primary vector of human dengue and yellow fever viruses; it is also considered the principal vector of Chikungunya virus in Asia. In particular, dengue and dengue hemorrhagic fever constitute an important burden to humankind in terms of morbidity and mortality. About 3.6 billion people in the tropics, mainly in Asia, the Western Pacific region, the Caribbean, and Central and South America, live under risk of infection with one or more of the four dengue virus serotypes (DEN-1 to DEN-4), and recent reports estimate over 230 million infections, over 2 million cases of the severe form of the disease, and 21,000 deaths.\n(Párrafo extraído del texto a modo de resumen)</i

Berón, Corina M.

Díaz Nieto, Leonardo M.

Maciá, Arnaldo

Perotti, María Alejandra

Centro de Servicios en Gestión de Información

ViewpointsGeographical Limits of the Southeastern Distribution ofAedes aegypti (Diptera, Culicidae) in ArgentinaLeonardo M. Dı´az-Nieto1, Arnaldo Macia´2, M. Alejandra Perotti3, Corina M. Bero´n1*1Centro de Estudios de Biodiversidad y Biotecnologı´a (CEBB-CIB-FIBA-Mar del Plata) – CONICET, Mar del Plata, Argentina, 2Divisio´n Entomologı´a, Facultad de CienciasNaturales y Museo de La Plata (UNLP), La Plata, Argentina, 3 School of Biological Sciences, University of Reading, Reading, United KingdomBackgroundAedes aegypti (Linnaeus) is a human-bitingmosquito and the primary vector ofhuman dengue and yellow fever viruses;it is also considered the principal vector ofChikungunya virus in Asia [1,2]. Inparticular, dengue and dengue hemor-rhagic fever constitute an important bur-den to humankind in terms of morbidityand mortality. About 3.6 billion people inthe tropics, mainly in Asia, the WesternPacific region, the Caribbean, and Centraland South America, live under risk ofinfection with one or more of the fourdengue virus serotypes (DEN-1 to DEN-4),and recent reports estimate over 230million infections, over 2 million cases ofthe severe form of the disease, and 21,000deaths [3].It is believed that A. aegypti originallymigrated from West Africa to the Northand South America in the 15th centuryaboard slave ships, after which yellowfever appeared in the New World. Pre-sumably the yellow fever virus was intro-duced by travellers on these ships, espe-cially African slaves. The adaptation ofthis insect to survive in human environ-ments was crucial for colonization anddevelopment in water storage containersin the holds of sailing ships [4]. At present,A. aegypti lives in close proximity to people,in urban areas, breeding in all types ofdomestic and peridomestic collections offresh water, including flower vases, waterdrums, tins, broken coconut shells, oldtires, and gutters. A major range ofexpansion of Aedes mosquitoes into theseurban areas is also attributable to theadaptation of the genera Aedes to breed inwater-holding automobile tires [5].A. aegypti is a tropical and subtropicalspecies spanning a geographical distribu-tion from 35uN to 35uS. Its lower thermalthreshold corresponds to 10uC isothermsduring the winter, and although it has beenfound up to 45uN, its presence in colderregions is due to its ability to colonize newareas during the warm season [6]. In SouthAmerica, the historic direction of dispersalof Aedes mosquitoes has been towardshigher latitudes and from tropical tosub-tropical areas, in particular in theSouthern Cone. We propose that thesoutheastern movement of A. aegypti mightbe related to human migrations from ruralareas to towns lacking in a proper housingpolicy and essential services like water, andsewage disposal systems (http://www.migraciones.gov.ar/pdf_varios/estadisticas/Patria_Grande.pdf) [7].Between the 1950s, 1960s, and most ofthe 1970s, epidemic dengue was rare inCentral and South America because A.aegypti had been eliminated from most ofthe countries. The eradication programorganized by the Pan American HealthOrganization (PAHO) was discontinued inthe early 1970s, and consequently themosquito was reintroduced in countriesfrom which it had been eradicated [6,8].In Argentina, the earliest records of A.aegypti go back to the 1900s and areconcurrent with the dengue-like epidemicof 1916, which affected the coastal areas ofthe Uruguay River (31u449S, 60u319W)[9]. However, in 1986 re-infestation tookplace along the northern border withParaguay, spreading over wide areas ofthe country. Nowadays, the current geo-graphical distribution of A. aegypti inArgentina is wider than during its eradi-cation in 1967 [10,11]. Recently it hasbeen demonstrated that the three A. aegyptimain haplogroups identified in Argentinarepresent different colonization events,probably from neighboring countries:Bolivia, Paraguay, and Brazil (Figure 1Aand 1B) [7]. Particularly, in Buenos AiresProvince, the most densely populated areaof the country, the records of highabundances of well-established popula-tions of A. aegypti were taken in La Plata(capital of the province) and in BuenosAires (capital city of the country), bothlocated on the east coast, and the south-ernmost findings were recorded in Chas-comu´s, 132 km from Buenos Aires city(35u339S, 58u009W, Figure 1) [10–15].On the other hand, cases of dengue haveincreased in the last few years in Argentina.From January to June 2012, 2,043 patientswith symptoms were reported, and 194 wereconfirmed with serotypes DEN-1, DEN-2, orDEN-3 (http://www.msal.gov.ar/dengue/images/stories/partes_dengue/parte74.pdf).In 2011 PAHO released an epidemiologicalalert due to the introduction of DEN-4serotype in the Americas (http://new.paho.org), with Brazil, Paraguay, and Boliviacountries at high risk of dengue infectionwith 57,267 possible cases and 5 deaths(Brazil); 10,827 suspected cases and 30deaths (Paraguay); and 3,233 notified caseswith 28 deaths (Bolivia) (Figure 1B) (http://www.msal.gov.ar/dengue/images/stories/partes_dengue/parte74.pdf).In the United States, the dispersal ofAedes albopictus Skuse offered an opportu-nity to understand the synanthropic be-havior of Aedes mosquitoes. The mosquitowas introduced in 1985 in the continentalterritory through shipments of used tiresfrom Asia that contained eggs [16]. Insubsequent years, the pattern of spread ofthis container-dwelling species followedthe main interstate highways [17], quicklyreaching and colonizing several new areasCitation: Dı´az-Nieto LM, Macia´ A, Perotti MA, Bero´n CM (2013) Geographical Limits of the SoutheasternDistribution of Aedes aegypti (Diptera, Culicidae) in Argentina. PLoS Negl Trop Dis 7(1): e1963. doi:10.1371/journal.pntd.0001963Editor: Scott L. O’Neill, Monash University, AustraliaPublished January 31, 2013Copyright: ß 2013 Dı´az-Nieto et al. This is an open-access article distributed under the terms of the CreativeCommons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium,provided the original author and source are credited.Funding: This investigation was supported by Agencia Nacional de Promocio´n Cientı´ca y Tecnolo´gica(ANPCyT PICT-2007-02069) and by the Universidad Nacional de Mar del Plata (grant 15E/329 EXA 382/07). Thefunders had no role in study design, data collection and analysis, decision to publish, or preparation of themanuscript.Competing Interests: The authors have declared that no competing interests exist.* E-mail: cberon@fiba.org.arPLOS Neglected Tropical Diseases | www.plosntds.org 1 January 2013 | Volume 7 | Issue 1 | e1963of the US in a few years. We wonderedwhether A. aegypti would present a similarbehavior, and is making use of humantransportation [18]. For this, we investi-gated the occurrence of the mosquito inmajor roads connecting densely populatedcities with the southeast of Argentina(Table 1).One of the most important highways inArgentina is Provincial Route Nu2, whichconnects Buenos Aires and La Plata citieswith Mar del Plata city and the mostvisited beaches of the country, principallyin the summer time, representing about 2million people commuting between thoseFigure 1. Aedes aegypti and dengue fever in South America. (A) Historical distribution of A. aegypti in Argentina, indicating 1916, the firstdengue-like epidemic; 1986, re-infestation locations; and biogeographical records between 1991 and 1999. (B) Current geographic distribution of A.aegypti and regions with risk of transmission of dengue in South America. (C) Studied area, showing highways between Buenos Aires and Mar delPlata cities, sampling points, and distances between them. (A and B) adapted from Curto et al., Vezzani and Carbajo [10,15], and http://www.healthmap.org/dengue/index.php.doi:10.1371/journal.pntd.0001963.g001PLOS Neglected Tropical Diseases | www.plosntds.org 2 January 2013 | Volume 7 | Issue 1 | e1963places (Figure 1C and Table 1) (http://www.indec.mecon.ar). Route Nu2 crossesthe most prominent wetland areas of thePampas, and its construction has definitelyreshaped the landscape, making availablenew humanmanmade wetlands that offershelter to an increasing diversity of floraand fauna, including mosquitoes [19]. Onthis artery there are some small towns thatoffer several travel services such as tire-repair stations, or ‘‘gomerı´as’’, which storeused automobile and truck tires for longperiods of time; thus these tires accumu-late rainwater (Figures 2 and 3A). More-over, along this highway many vehiclestransport goods from the north of thecountry to the coastal area without anysanitary control to prevent insect exchangefrom one region to the other. The latestscientific southernmost record of A. aegyptidetected in Buenos Aires Province wasobtained in Chascomu´s, a town located onRoute Nu2 [11]. Route Nu2 takes the bulkof the traffic and people in a southeasterndirection. On the other hand, RouteNu11, connecting Buenos Aires and LaPlata cities with the Atlantic coast, is ashort motorway parallel to the coastline,and Route Nu226 runs southwest and ismostly used by freight transport(Figure 1C).Present Distribution of A.aegypti in the Most PopulatedAreas of Buenos Aires ProvinceIn order to understand the status of thesouthern distribution of A. aegypti, wesampled mosquito larvae and pupaeduring the rainy period, in January andMarch 2011, and only in March 2012,because rainfall levels were very low inTable 1. Characteristics of cities connected by Route Nu 2 in Buenos Aires Province (http://www.censo2010.indec.gov.ar/).City Area (km2) Population Size Number of HouseholdsBuenos Aires 2,681 12,801,365 3,147,638Chascomu´s 3,452 38,477 18,277Lezama 1,102 4,111 NdbCastelli 2,063 8,206 3,448Dolores 1,973 26,601 10,687General Guido 2,814 2,814 1,508Maipu´ 2,641 10,172 4,375Mar del Plata 1,461 618,989 308,570MdP, summer timea 1,461 2,000,000 NdbaMdP, Mar del Plata.bNo data.doi:10.1371/journal.pntd.0001963.t001Figure 2. Weather conditions of the studied area, from July 2010 to June 2012. On the left mean temperature in uC (T), on the right % ofrelative humidity (RH) and total precipitation in mm (PP). http://www.tutiempo.net/clima. Arrows indicate sampling times.doi:10.1371/journal.pntd.0001963.g002PLOS Neglected Tropical Diseases | www.plosntds.org 3 January 2013 | Volume 7 | Issue 1 | e1963January 2012 (Figure 2). The samplingstations were located in towns situatedalong Route Nu2 and the other two majorarteries that connect Buenos Aires with thesouth. The sampling stations were ceme-teries that are far from the towns and areinfrequently visited, and gomerı´as locatedin densely populated areas of each town,both at the edge of the roads (Figure 3 andTable 2). Larval specimens were collectedand reared until fourth instar or adultstage to facilitate identification usingspecific keys [13,20]. Voucher specimens,prepared from all localities, were submit-ted to the local museum, Museo deCiencias Naturales ‘‘Lorenzo Scaglia’’(Mar del Plata, Argentina).Larvae of A. aegypti were found in March2011 and 2012 in Chascomu´s, agreeingwith and confirming previous records[11,13]. Here we report the finding of A.aegypti in the towns of Lezama, Castelli,and Dolores, to our knowledge for the firsttime. A population of mosquitoes wasfound in Lezama in March 2011, 39.2 kmsoutheast of Chascomu´s; both localities areseparated by farmland and uniquelyconnected by Route Nu2. As a highnumber of larvae of all stages and pupaewere found in multiple containers inLezama, we feel confident that this localityholds a natural, well-established popula-tion. In March 2012, we found a highernumber of larvae of all stages and pupae inthe same type of containers for a secondtime in Lezama, and for the first time inCastelli (27.7 km south from Lezama) andDolores (59.5 km south from Lezama),making Dolores the southernmost limit ofFigure 3. Sampling locations in Buenos Aires province. (A) Tire-repair stations showing tires with accumulated rainwater. (B) Flowerpots atcemeteries.doi:10.1371/journal.pntd.0001963.g003PLOS Neglected Tropical Diseases | www.plosntds.org 4 January 2013 | Volume 7 | Issue 1 | e1963the species’ range within Argentina, now98.7 km south of Chascomu´s (Figure 1C).In Routes Nu11 and 226, A. aegypti was notfound in any of the water containersexamined.In the south of Argentina, A. aegypti isvery likely to be moving by passivedispersal using the major highway con-necting the north with the southeast of thecountry. It is noteworthy that this samebehavior has been studied and document-ed in a closely related species A. albopictusin the US. Previous observations on thismosquito in North America are consistentwith the hypothesis of mosquito migrationfacilitated by anthropic action, presumablyby transportation of scrapped tires throughthe interstate highway system [17]. In A.aegypti, egg resistance in the absence ofwater, a feature shared with A. albopictus,can lead to a similar way of transferring tonew places in order to breed. Therefore,passive dispersal of Aedes species usingfrequented freeways should be consideredwhen designing new A. aegypti monitoringprograms.According to Shepherd et al. [21],dengue virus transmission follows twogeneral patterns: epidemic dengue andhyperendemic dengue. Epidemic denguetransmission occurs when dengue virus isintroduced into a region as an isolatedevent that involves a single viral strain. Ifthe number of vectors and susceptiblehosts are sufficient, explosive transmissioncan occur with an infection incidence of25%–50%. Hyperendemic dengue trans-mission is characterized by the circulationof multiple viral serotypes in an area withsusceptible hosts and competent vector(with or without seasonal variation) andappears to be a major risk for denguehemorrhagic fever. Travelers to theseareas are more likely to be infected thantravelers going to areas that experienceonly epidemic transmission.In South America, particularly in Bue-nos Aires Province, it is known that theprovincial health ministry has a programof surveillance of A. aegypti, which involvesthe monitoring and control of mosquitolarvae and eggs. However, this surveil-lance does not follow a regular pattern,being erratic in terms of time, and eachcouncil or municipality decides whether tocarry it on or not. In addition, sometimesit is difficult to obtain official data.The new biogeographical record ofcentral and southern Argentina, reportedin this article, is an important fact of theconstant expansion of A. aegypti into newsouthernmost areas. Together with thepresence of the different dengue serotypes,this expansion indicates that the situationis far more dangerous than previouslythought. Urgent and responsible actionsmust be taken to control the dengue vectorand its expansion into new areas.AcknowledgmentsWe especially thank Prof. Ana Tassi for criticalrevision of the manuscript. LMDN is a PhDstudent at the National University of Mar delPlata. AM is Research Assistant of Comisio´n deInvestigaciones Cientı´ficas (CIC), Argentina.CMB is a Research Fellow. This work is partof LMDN’s PhD thesis.References1. Becker N, Petric´ D, Zgomba M, Boase C, DahlC, et al. (2003) Mosquitoes and their control. NewYork. Kluwer Academic/Plenum Publishers. 498p.2. Pialoux G, Gau¨ze`re BA, Jaure´guiberry S, StrobelM (2007) Chikungunya, an epidemic arbovirosis.Lancet Infect Dis 7: 319–327.3. Gubler DJ (2012) The economic burden ofdengue. Am J Trop Med Hyg 86: 743–744.4. Lounibos LP (2002) Invasions by insect vectors ofhuman disease. Annu Rev Entomol 47: 233–266.5. Berry WJ, Craig GB (1984) Bionomics of Aedesatropalpus breeding in scrap tires in northernIndiana. Mosq News 44: 476–484.6. Pan-American Health Organization (1994) Den-gue and dengue hemorrhagic fever in theAmericas: guidelines for prevention and control.Washington: PAHO Scientific Publication Nu548. 98 p.7. Albrieu Llina´s G, Gardenal CN (2012) Phyloge-ography of Aedes aegypti in Argentina: long-distance colonization and rapid restoration offragmented relicts after a continental controlcampaign. Vector Borne Zoon Dis 12: 254–261.8. Gubler DJ (1998) Dengue and dengue hemor-rhagic fever. Clin Microbiol Rev 11: 480–496.9. Gaudino NM (1916) Dengue. Rev San Mil 15:617–627.10. Curto SI, Boffi R, Carbajo AE, Plastina R,Schweigmann N (2002) Reinfestacio´n del territorioargentino por Aedes aegypti. Distribucio´n geogra´fica(1994–1999). In: Salomo´n OD. Actualizaciones enArtropodologı´a sanitaria Argentina. Buenos Aires:Fundacio´n Mundo Sano. pp. 127–137.11. Rossi GC, Lestani EA, D’Oria JM (2006) Nuevosregistros y distribucio´n de mosquitos de laArgentina (Diptera: Culicidae). Rev Soc EntomolArgent 65: 51–56.12. Macia´ A (2006) Differences in performance ofAedes aegypti larvae raised at different densities intires and ovitraps under field conditions inArgentina. J Vector Ecol 31: 371–377.13. Rossi GC, Mariluis JC, Schnack JA, Spinelli GR(2002) Dı´pteros vectores (Culicidae y Calliphor-idae) de la provincia de Buenos Aires. La Plata:COBIOBO Nu 4. PROBIOTA Nu 3. 45 p.14. Schweigmann N, Orellano P, Kuruc J, Vera TM,Vezzani D, et al. (2002) Distribucio´n y abundan-cia de Aedes aegypti (Diptera: Culicidae) en laciudad de Buenos Aires. In: Salomo´n OD.Actualizaciones en Artropodologı´a sanitaria Ar-gentina. Buenos Aires: Fundacio´n Mundo Sano.pp. 155–160.15. Vezzani D, Carbajo AE (2008) Aedes aegypti, Aedesalbopictus, and dengue in Argentina: currentknowledge and future directions. Mem InstOswaldo Cruz 103: 66–74.Table 2. Sampling stations and species collected in cities along Route Nu 2, in the southeast of Argentina.City 2011 2012FlowerpotsaCulexsp.A.aegyptiTire-RepairStationsbCulexsp.A.aegypti FlowerpotsaCulexsp.A.aegyptiTire-RepairStationsbCulexsp. A. aegyptiChascomu´s 239 (12/0) + 2 1 (1/1) + + 300 (8/2) + + 2 (2/2) + +Lezama 200 (0/0) 2 2 3 (3/1) + + 200 (5/0) + 2 3 (3/3) + +Castelli 480 (0/0) 2 2 3 (3/0) + 2 200 (3/2) + + 3 (3/3) + +Dolores 730 (29/0) + 2 2 (2/0) + 2 400 (12/1) + + 2 (2/2) + +Gral. Guido 280 (1/0) + 2 2 (2/0) + 2 300 (7/0) + 2 3 (3/0) + 2Maipu´ 440 (5/0) + 2 2 (2/0) + 2 ndc ndc ndc 2 (1/0) + 2Mar del Plata 3,600 (,45/0) + 2 10 (8/0) + 2 3,600 (,45/0) + 2 10 (8/0) + 2aNumber of flowerpots sampled, in brackets positive ones for Culex sp. and for A. aegypti, respectively.bThe number of A. aegypti was 500 larvae or more in each tire-repair station, in brackets positive ones for Culex sp. and for A. aegypti, respectively.cNo data.doi:10.1371/journal.pntd.0001963.t002PLOS Neglected Tropical Diseases | www.plosntds.org 5 January 2013 | Volume 7 | Issue 1 | e196316. Sprenger D, Wuithiranyagool T (1986) Thediscovery and distribution of Aedes albopictus inHarris County, Texas. J Am Mosq Control Assoc2: 217–219.17. Moore CG, Mitchell CJ (1997) Aedes albopictus inthe United States: ten-year presence and publichealth implications. Emerg Infec Dis 3: 329–334.18. Hemme RR, Thomas CL, Chadee DD, SeversonDW (2010) Influence of urban landscapes onpopulation dynamics in a short-distance migrantmosquito: evidence for the dengue vector Aedesaegypti. PLoS Negl Trop Dis 4: e634. doi:10.1371/journal.pntd.000063419. Schnack JA, de Francesco FO, Colado UR,Novoa ML, Schnack EJ (2000) Humedalesantro´picos: su contribucio´n para la conservacio´nde la biodiversidad en los dominios subtropical ypampa´sico de la Argentina. Ecologı´a Austral 10:63–80.20. Darsie RF, Mitchell CJ (1985) The mosquitoes ofArgentina. In: Lewis T. Nielsen. Mosquitosystematics. Utah: American Mosquito controlAssociation. pp. 153–253.21. Shepherd SM, Hinfey PB, Shoff WH (2009)Dengue. Available: http://emedicine.medscape.com/article/215840-overview. Accessed 7 Janu-ary 2013.PLOS Neglected Tropical Diseases | www.plosntds.org 6 January 2013 | Volume 7 | Issue 1 | e1963

Geographical limits of the Southeastern distribution of <i>Aedes aegypti</i> (Diptera, Culicidae) in Argentina

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Geographical limits of the Southeastern distribution of <i>Aedes aegypti</i> (Diptera, Culicidae) in Argentina

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