**4. Conclusions**

498 Current Topics in Tropical Medicine

*Ochlerotatus atropalpus*, have been also reported. *Oc. japonicus* is an Asian species and a competent vector of several arboviruses, including West Nile virus and Japanese encephalitis virus and is considered a significant public health risk (Sardelis & Turell, 2001; Sardelis et al., 2002a; 2002b; 2003). *Oc. japonicus* has been collected only in France, Belgium, Switzerland and Germany (Schafther et al., 2003; 2009; Becker et al., 2011). On the other hand *Oc. atropalpus* is endemic to North America and has been observed in Italy, France and Netherlands (Romi et al., 1997; Adege-EID Méditerranée, 2006; Scholte et al., 2009). Although in the field, *Oc. atropalpus* has not been evidenced as an important vector of infectious diseases, under laboratory conditions, the species has been proven as a competent vector for West Nile virus, Japanese encephalitis virus, Saint-Louis encephalitis virus La Crosse encephalitis virus, among other arboviruses (King, 1960; Turell et al., 2001). Globalization, especially traffic of used tires, has led the arrival of *Oc. japonicus* and *Oc. atropalpus* to Europe. Out of these exotic vectors, we can not forget or ignore the presence of potential indigenous vectors of dengue and yellow fever in Europe. For example, *Aedes vittatus* is an important vector of yellow fever in different parts of Africa (Lewis, 1943; Satti & Haseeb, 1966) and also a potential vector of Chikungunya and four dengue serotypes (Mourya & Banerjee, 1987; Mavale et al., 1992). Although the species is deeply distributed in Mediterranean region (Spain, Portugal, France and Italy), the studies about its biology and phenology have been scanty in Europe. Anyway it seems unlikely that *Ae. vittatus* could start a cycle of virus transmission to humans because of its high degree of ruralism. Moreover *Ochlerotatus geniculatus* is a dendrolimnic species endemic to Europe that can efficiently transmit yellow fever, but this possibility has been evidenced only in laboratory

Although a vaccine based on live attenuated virus of the strain 17D is available for yelow fever since years, currently we haven´t any vaccine to be used with full warranty against dengue. However, the need for a dengue vaccine is clear. The most effective measures of an integrated mosquito control program (including changes in human habitation and behavior, the use of insecticides, and long-lasting modification of natural and man-made mosquito habitats) are difficult to implement and largely unsuccessful in most poverty-stricken settings, and consequently have not been carried out comprehensively enough to limit dengue's spread. While vector control is an integral part of any dengue prevention strategy,

In recent years it has been obtained a better understanding of the disease and its etiopatogenicity, as well as of the necessary aspects to develop a vaccine that provides an effective and lasting protection against the virus. Dengue vaccine development is a very difficult task due to the possible participation of four related serotypes, since immunity to one serotype does not confer immunity to the remaining three. Complicating the scenario further is immune enhancement, which can result in severe dengue hemorrhagic fever or dengue shock syndrome in anyone who has been infected with one of the serotypes and subsequently becomes infected with another. Most of researchers agree that only effective solution is a tetravalent vaccine that simultaneously protects against all four serotypes. Regarding to this, it must be noted that tetravalent vaccines against dengue are currently in last phases of trials and is expected to be available for human population in the next

conditions (Roubaud et al., 1937).

it is not enough on its own.

following years.

**3.1 New challenges: The development of dengue vaccines** 

Although malaria's receptivity is still high in different parts of Europe, we may conclude that the malariogenic potential of the Old Continent is low. Fortunately socio-economic and sanitary conditions of most European countries also support this assertion. While it is true that infectivity studies should be further promoted, percentages of imported malaria cases remain very low. However we must pay some attention to the increasing trend of malaria importation in last years, as well as also awareness among tourists and VFR's for to take corresponding prophylactic measures during their travels to endemic areas. Anyway, sporadic and local cases of autochthonous transmission mainly transmitted by *An. atroparvus, An. labranchiae, An. sacharovi* and/or *An. plumbeus*, can not been discarded in next years.

On the other hand, the answer to the question about if should be expected the re-emergence of dengue and other mosquito-borne tropical viruses in Europe in next years is indubitable: definitively yes. The arrival, establishment and expansion of dengue urbanite vectors due to global changes such as globalization, climate change and the lack of effective mosquito control programs, together with the increasing of imported cases in humans provokes that local and intense transmission of dengue could be a reality in next years in Southern Europe. To cope this possibility is necessary to enhance the entomological surveillance in potential areas of mosquitoes importation, such as airports or seaports, strength the monitoring of tropical viruses imported and awareness among citizens about their role in mosquito control and best prophylactic measures to take during the travels to tropical regions.
