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of D. repensinfection had been reported for Italy. However, between 1995 and 2000, 117 more cases were registered in Italy Pampiglione, Canestri Trotte Rivasi, 1995;
Pampiglione Rivasi, 2000. Of these recent cases, no human deaths have been reported and some human infections were asymptomatic; for the infections that were symptoma-
tic, the symptoms were usually subcutaneous and pulmonary nodules or parenchymal lesions. Evidence from serological data, however, suggests that people living in endemic
areas are infected to a similar extent up to 30 and more as the canine populations Simón et al., 2005. Because imported dogs are seldom examined for parasitic infections,
the increasing commercialized and sometimes illegal import of dogs from southern to central Europe – especially to Germany, where there are vector-competent mosquito
species Rossi et al., 1999 – gives reason to fear cases of autochthonous canine and human dirofilariasis in central Europe in the near future. In fact, the first case of autochthonous
infection in a dog was recently demonstrated for Germany Hermosilla et al., 2006.
11.5. The spread of mosquitoes and mosquito-borne pathogens
The significant increase in international travel and trade in consumer goods and animals offers multiple chances for insects and infected vertebrate hosts to be transported across
natural barriers, such as mountains, oceans and climate zones. Examples already mentio- ned are: the assumed illegal import of WNV-infected birds, which led to the emergence
of West Nile fever in the Americas; the intercontinental travel of Plasmodium-infected Anopheles
-mosquitoes by aircraft, which possibly caused cases of airport or baggage mal- aria; and the import of dogs infected with filaria, which caused heartworm disease.
People who travel can also harbour vector-borne pathogens obtained from endemic areas, such as malaria parasites, dengue virus or chikungunya virus. In 2003, the CDC received
reports of 1278 cases of malaria among people in the United States, 1268 of them impor- ted Eliades et al., 2005. For the same year, 11573 imported cases of malaria in Europe
were reported to the WHO Regional Office for Europe 2006, with major contributions by France 6392 estimated cases, 3511 of them confirmed, the United Kingdom 1722
confirmed cases and Germany 819 confirmed cases. For the same year, 166 travel-rela- ted cases of dengue fever were documented in the WHO Regional Office for Europe
centralized information system for infectious diseases CISID data bank for Europe. As with dengue fever, however, several countries do not report their cases regularly, and
France, which made no report in 2003, counted 3157 cases of dengue fever in 2004. In the United States, the CDC identified 77 cases of dengue fever in 37 states and the District
of Columbia, from 2001 to 2004 Beaty et al., 2005. However, as dengue fever is not a nationally notifiable disease in the United States, this figure is likely subject to underre-
porting. Only recently, more than 160 cases of chikungunya disease were imported in less than a year to several European countries from Indian Ocean islands see subsection
11.4.4 – particularly to France, due to traditionally close ties.
Although the number of imported cases of mosquito-related infections is not dramatic from an epidemiological perspective, it is sufficient to expect sporadic local transmission
last decade, malaria infections have occurred in some tropical holiday resorts that had been previously free of malaria and where no prophylaxis had been necessary, such as
parts of the Dominican Republic Kay et al., 2005. On the other hand, visitors from mal- aria-endemic regions often ignore the possibility that they might be infected with mal-
aria, as they are not sick due to the semi-immunity acquired from repeated infection since childhood. Due to indigenous vector-competent Anophelesspp. in Europe for example,
Anophelessacharovi
, Anopheles atroparvusand Anopheles labranchiae that take their blood- meals on gametocyte-carrying people single locally acquired malaria cases have been
occurring in Bulgaria, Greece, Germany, Italy and Spain during the last 17 years Sartori et al., 1989; Nikolaeva, 1996; Baldari et al., 1998; Krüger et al., 2001; Cuadros et al., 2002;
Kampen et al., 2002.
In the United States, Anopheles freeborni, Anopheles quadrimaculatusand Anopheles pseudo- punctipennis
are considered to be the primary malaria vectors. During the last two deca- des, autochthonous malaria cases have occurred in California Maldonado et al. 1990,
New Jersey Brook et al., 1994; Shah et al., 2004, Houston CDC, 1995, New York City Layton et al., 1995, Virginia Shah et al., 2004, Florida Selover et al., 2004 and
Maryland Eliades et al., 2005.
Sometimes, imported infected mosquitoes may provoke cases of so-called airport mal- aria or baggage malaria. Between 1969 and 1997, 63 cases of malaria associated with air-
ports were recorded in western Europe Isaacson, 1989; Castelli et al., 1993; Mouchet, 2000. Such infected Anopheles mosquitoes originate from airports located in zones of
endemic transmission, mostly sub-Saharan Africa. Local transmissions in the proximity of destination airports in non-endemic regions may occur during the summer and, par-
ticularly, during so-called hot years. The infections are extremely difficult to diagnose when people who fall ill have no recent history of travelling to malarial areas. Disinfection
of aircrafts can minimize the risk of such cases WHO, 1995; Guillet et al., 1998; Gratz, Steffen Cocksedge, 2000.
11.4.6. Dirofilariasis
Human dirofilariasis seems to be a more significant problem in Europe than in North America. It is caused by an opportunistic infection with filarial worms Dirofilaria tenuis
and Dirofilaria immitis in North America; Dirofilaria repens and D. immitis in Europe, leading to heartworm disease in their natural canine hosts and sometimes in felines.
Possible vectors are various species of the mosquito genera Culex, Anopheles and Aedes Pampiglione, Canestri Trotte Rivasi, 1995, including the Asian tiger mosquito
Cancrini et al., 2003a,b.
While there are few human cases in the United States, canine dirofilariasis is endemic in southern Europe. Also, human infections with the major parasite D. repens have been
increasing for several decades in France, Greece and Spain, and especially in Italy Pampiglione, Canestri Trotte Rivasi, 1995; Muro et al., 1999; Pampiglione Rivasi,
2000. Until the middle of the last century, human dirofilariasis was considered excep- tional, and from its first demonstration in 1864 until 1995, a total of only 181 human cases
by indigenous vector-competent mosquitoes that become infected by biting local people who have acquired infections abroad. Also, although endemic malaria has been eradica-
ted from Europe and the United States, the mosquitoes capable of transmitting malaria are still widely distributed see subsection 11.4.5. The primary dengue virus vector, the
yellow fever mosquito, has been successfully eradicated from Europe see subsection 11.4.3, but not from the United States. Recently, some non-indigenous mosquito species
such as the Asian tiger mosquito that are vector-competent for dengue virus, chikun- gunya virus and several other arboviruses have been introduced to Europe and the Unites
States through trade in used tyres and lucky bamboo Dracaena spp.. After introduction, these non-indigenous mosquito species have often survived and spread into other areas
of their new country.
Anthropogenic transportation and active spread are the causes of the emergence of the Asian tiger mosquito in the Western world. It was introduced from its South-East Asian
home by the used tyre trade and, after a period of adaptation, began to spread Knudsen, Romi Majori, 1996. In the United States, it was first detected in Texas, in 1985
Sprenger Wuithiranyagool, 1986, and in 2000 it was established in 866 counties in 26 states CDC, 2000. In 2003, however, it was recorded for the first time in Colorado
Bennett et al., 2005. In Europe, the Asian tiger mosquito first appeared in Albania, in 1979 Adhami Reiter, 1998, and about 10 years later, in 1990, in Italy Sabatini et al.,
1990. The Italian strain of Asian tiger mosquito was imported from the United States, where it adapted to more moderate climate conditions by diapause overwintering after
its introduction from South-East Asia Rightor, Farmer Clarke, 1987; Knudsen, Romi Majori, 1996. It soon became widely distributed in southern Europe, and in 1999 it
was found in Normandy, in northern France Schaffner et al., 2001b. A year later, in 2000, it was found in Belgium Schaffner, van Bortel Coosemans, 2004, which had
been predicted previously as an area of minor distribution risk Knudsen, Romi Majori, 1996. More recently, it was recorded in Montenegro, in 2001 Petri´c et al., 2001; in
Switzerland, in 2003 Flacio et al., 2004; in Croatia and Spain, in 2004 Aranda, Eritja Roiz, 2006; Klobuˇcar et al., 2006; and in Bosnia and H erzegovina, Greece, the
Netherlands and Slovenia, in 2005 Samanidou-Voyadjoglou et al., 2005; Petri´c et al., 2006; Scholte et al., 2006 Fig. 11.1.
The Asian tiger mosquito is an efficient vector of numerous arboviruses, including den- gue, chikungunya and probably West Nile viruses Mitchell, 1995. Dengue fever used
to be endemic in Europe some time ago and was associated with high mortality rates Cardamatis, 1929; Rosen, 1986.
The rock pool mosquito Aedes atropalpus, which is a vector of EEEV in the United States, has been introduced to southern Europe by used tyres from North America.
However, it was then eradicated from two introductory locales in central Italy Romi, di Luca Majori, 1999; Snow Ramsdale, 2002 and western France F. Schaffner, perso-
nal communication, 2003 during Asian tiger mosquito control campaigns.
The Asian bush mosquito Aedes japonicus japonicus is a vector of Japanese encephalitis virus and has also been found infected with WNV. It has invaded Europe and the United
Public Health Significance of Urban Pests
Mosquitoes
359 358
States from Asia. In the United States, it was recor-
ded for the first time in the states of New York and
New Jersey in 1998 Peyton et al., 1999. In Europe, it
was recorded for the first time in north-western
France in 2000 Schaffner, Chouin Guilloteau, 2003
a
n d
in Belgium in 2002 F.Schaffner, personal com-
munication, 2002.
11.6. National reporting and
