Aedes albopictus (Skuse, 1894): current status and records of an important invasive mosquito species in Spain

Palabras clave: Aedes albopictus, arbovirus, control de vectores, especies invasoras, salud pública, España.

Recibido el 26/02/2010 Aceptado el 09/05/2010

Although invasive alien species (IAS) are considered one of the most important threats to biodiversity, it is well known that the impact of some of them strongly and directly affect public health, their influence being secondary or null on native species in terms of "interspecific competition". Inside this group of IAS we can situate the Asian tiger mosquito, Aedes albopictus (Skuse, 1894), in a worrying preferential place (ISSG, 2009. http://www.issg.org/database/species/ecology.asp?si=109&fr=1&sts [Consulted: 2010, February, 11]). The main reason of this concern lies not only in the nuisances associated with their intense anthropophilic behavior, but also for its ability to act as a vector of arboviruses such as Dengue, Yellow Fever, West Nile, Chikungunya or Sindbis. Concerning the "interspecific competition", a term understood as any mechanism that produces negative effects on population growth of the native or focal species (Juliano & Lounibos, 2005. Ecol. Lett., 8: 558-574), the investigations are scanty and the results also less clarifying for invasive mosquitoes.

However some authors have proposed the appearance of competence situations related to the production of several water-borne substances (Sunahara & Mogi, 2002. Ecol. Entomol., 27: 346-354), mating behaviour (Ribeiro and Spielman, 1986. Amer. Nat., 128: 513–528) or delays in hatching (Edgerly et al., 1993. Ecol. Entomol., 18: 123-128). The ecological flexibility of Ae. albopictus allows it to colonize many types of man-made sites such as cemetery flower pots, abandoned containers or used tires, among others (Hawley et al., 1987. Science, 236: 1114-1116; Bueno Marí & Jiménez Peydró, 2009. Enf. Emerg., 11: 30-35), being consequently a great aquatic invader in several water microhabitats. Therefore, it has gone from being just a strictly tree hole mosquito of the Asian jungle to becoming an urban mosquito currently present in all continents.

The first trapping of Ae. albopictus in Europe occurred in Albania in 1979, probably due to the introduction of indigenous populations from China (Adhami & Reiter, 1998. J. Am. Mosq. Control Assoc., 14: 340-343). Since then, sixteen European countries have detected Ae. albopictus at least once in their territory (ECDC, 2009. Technical Report. Development of Aedes albopictus risk maps, pp: 1-45). However this number could be an underestimation due to the absence of Ae. albopictus surveillance in many countries of the Old Continent. In countries like Italy, where Ae. albopictus arrived in 1990, this invasive mosquito is currently colonizing two thirds of the territory, causing an expenditure of about 10-15 millions of Euros in control strategies (Pilani et al., 2004. Abstracts book of the 3rd Third EMCA Workshop) and being responsible of an outbreak of Chikungunya virus in 2007 (Seyler et al., 2008. Euro Surveill. 13 (3) http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=8015 [Consulted: 2010, February, 11]).

The cosmopolitanism of the Asian tiger mosquito is closely related to several commercial and tourist human actions, taking even more into account the short flight range of the imago (Eritja et al., 2005. Biol. Invasions, 7: 87-97). The eggs of Ae. albopictus can withstand desiccation, which allows them to survive long journeys around the world in a variety of containers. Therefore, dispersions have been determined by the presence of eggs in used tires (Reiter & Sprenger, 1987. J. Am. Mosq. Control Assoc., 3: 494-501) and garden products associated with "Lucky Bamboo" (Dracaena spp.) (Madon et al., 2002. J. Vector Ecol., 27: 149-154), as well as accidental transport with adults inside vehicles (Flacio et al., 2004. Boll. Soc. Ticin. Sci. Nat., 92: 141-142).

In Spain, Ae. albopictus was first caught in Sant Cugat del Vallès (Catalonia, Spain) in 2004 (Aranda et al., 2006. Med. Vet. Entomol., 20: 150-152) promoted by an increase of medical visits resulting from the nuisance of their aggressive bites (Giménez et al., 2007. Gac. Sanitaria, 21: 25-28). In this country, until the year 2009 a total of 87 municipalities of Catalonia (NE of Spain) and 2 municipalities of Alicante (SE of Spain) detected Asian tiger mosquito population in their territories (Roiz et al., 2007. Bol. SEA, 40: 523-526; GCAT, 2008. Caracterització de la población del mosquit tigre asiàtic (Aedes albopictus) a Catalunya, pp: 1-66; Bueno Marí et al., 2009a. Bol. Asoc. Esp. Entomol., 33: 529-532). All the information about these records is provided in Table I. Depending on the different regions, the mosquito control is carried out by private or public entities in Spain. Two of the five Mosquito Control Services (SCM) that are active in Spain have detected Ae. albopictus in their working areas. These SCM, together with various public research centers, are currently working intensely in distribution and spreading assessment as well as in the management and advice of satisfactory control measures against the Asian tiger mosquito (Roiz et al., 2008. J. Med. Entomol., 45: 347-352; Eritja, 2009. Abstracts book of the 5th European Mosquito Control Association Workshop, pp: 88-89; Bueno Marí et al., 2009b. Rev. Esp. Salud Pública, 83: 201-214).

Furthermore the European Centre for Disease Prevention and Control (ECDC) collaborates closely with experts in entomology to ensure a comprehensive understanding of the vector-related risk for introduction of arboviruses in Europe. Moreover, in 2002 the European Mosquito Control Association (EMCA) created a specific working group focused in the study of the status of Ae. albopictus in Europe due to the rapidity of its spread in the Old Continent. It is important to note that the surveillance of Ae. albopictus allowed the discovery of other exotic treehole species, also with a high vectorial capacity, such as Aedes japonicus (Theobald, 1901), Aedes atropalpus (Coquillett, 1902) or Aedes aegypti (Linnaeus, 1762) in several European countries (Romi et al., 1997. J. Am. Mosq. Control Assoc., 13: 245-246; Schaffner et al., 2003. J. Am. Mosq. Control Assoc., 19: 1-5; Almeida et al., 2007. Euro Surveill. 12 (46) www.eurosurveillance.org/ViewArticle.aspx?ArticleId=3311 [Consulted: 2010, February, 11]; Scholte et al., 2009. Euro Surveill. 14 (45) http://www.eurosurveillance.org/images/dynamic/EE/V14N45/art19400.pdf [Consulted: 2010, February, 11]). Nevertheless, control measures directed against Ae. albopictus also enabled the elimination of some of these species in different territories (Romi et al., 1999. J. Am. Mosq. Control Assoc., 15: 425-427).

In conclusion, we must pay attention to the dispersal and seasonal abundance of this invader mosquito with the aim of preventing possible scenarios of emergence and/or reemergence of several imported diseases in recent years in Spain such as Dengue or Chikungunya (Martín-Farfán et al., 2008. Enferm. Infecc. Microbiol. Clin., 26: 343-344; Reiter, 2010. Euro Surveill. 15 (10) http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19509 [Consulted: 2010, March, 15]; Bueno Marí and Jiménez Peydró, 2010. Gac. Sanit., in press). Although the eradication of Ae. albopictus would not be a realistic goal, we also should intensify and improve the control operations in order to limit its dispersion toward the Iberian Peninsula (Eritja et al., 2005. Op. cit.; Bueno Marí et al., 2009b. Op. cit.).