impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 117-119, 2008
An overview of the lesson learned in almost 20 years of fight
against the “Tiger” mosquito
R. Romi, G. Majori
Reparto di Malattie Trasmesse da vettori e Sanità Internazionale, dipartimento M.I.P.I., Istituto Superiore di Sanità, Roma
Introduction
Abstract. Since its introduction in Italy in 1990, Aedes albopictus has spread quickly across the country,
being at present reported in scattered foci in all regions below 600 m of altitude. The most important items
of the lesson learned in almost 20 years of fight against the “Tiger” in Italy are here reported and discussed.
Keywords: Aedes albopictus, Vector Borne diseases, Italy, Strategies of survival, Overwintering
Establishment and spread of the Asian tiger mosquito
Aedes albopictus in Italy and, at present also in other
European countries, as well as the increase of imported
cases of Aedes-borne viruses such as Chikungunya and
Dengue, raise the question of risk that also these tropical
diseases become stable in Europe.
As a matter of fact Chikungunya and Dengue arboviral
diseases are in expansion throughout the world. Aedes
aegypti, the principal vector of Dengue and Yellow Fever
in from disappeared in Europe since the late 1940’s while
populations of Ae. albopictus, established in Europe
recently and are spreading to most southern regions. In
laboratory experiments, this species has proven competent
for transmitting various viruses. At the same time
an increase of virus importation is observed due to
increased international travel. The Chikungunya fever
outbreak which occurred in July-October 2007 in Emilia-
Romagna confirmed that Europe is definitely at risk for
Aedes borne diseases. Since its introduction In Italy, Ae.
albopictus has represented the major human biting pest
throughout much of its range. But in Ravenna the species
has been proved to be responsible of the first outbreak of
a tropical arbovirus in Europe, shifting its role of simple
pest mosquito into of a dangerous vector. Despite that the
presence of the mosquito in our country it continues to be
considered by the Health Authorities as an environmental
problem no plan of emergence is going to be implemented.
Aedes albopictus in Italy: background.
Since its introduction in Italy in 1990, Aedes albopictus
spread quickly across the country. Although the first
record of adults of the species has occurred in Genova
(Liguria Region, North Western side), the most important
foci of colonization quickly developed in the North
Correspondence: Roberto Romi
Vector Borne Diseases and International Health Section,
Department of Infectious, Parasitic and Immunomediated
Diseases; Istituto Superiore di Sanità, Viale Regina Elena, 299
00161 Rome, Italy
Tel + 39 06 49902301, Fax + 39 06 49903561,
e-mail: roberto.romi@iss.it
Eastern Regions (Veneto, Friuli Venezia Giulia), along
the Adriatic Coast as well as in the inner lands (i.e.
Garda Lake or Euganei Hills), where the climate is
quite mild also during the winter. There the species has
found ideal environmental conditions for proliferating
and extending its seasonal activity.
Different populations of the tiger mosquito have been
probably introduced in Italy in separate periods and
from different areas, but we certainly demonstrated its
origin from the South of the USA (Atlanta, Georgia) in
containers of used tires. Most of these imported populations
of Ae. albopictus, although arrived in Italy after
a long period of “acclimation” in the USA, certainly
originated from areas located at the northern limit of
the natural distribution area where the species survives
in temperate countries through egg diapause induced
by the short photoperiod and by low temperatures.
In Italy, two major tire rethreading companies, located
in the outskirts of Padova and Bologna (Veneto and
Emilia Romagna Regions respectively), that imported
scrap tires directly from the USA, allowed the quick
spread of the mosquito across the country throughout
the internal trade of the tires sent to smaller companies.
During the first 4 years since the first entry, almost all
the new foci of colonization of Ae. albopictus were
recorded in areas close to tire deposits. Nevertheless
other kind of passive transportation certainly contributed
to the spread (the species enter spontaneously
cars, trucks and trains). At present scattered foci of the
Tiger mosquito are reported in all the Regions of the
country, with the exception of Valle d’Aosta, and in 82
out 107 Provinces, from coastal plains to inner lands,
up to 600 meters of altitude.
When in 1997, Ae. albopictus was detected in Rome,
we started to evaluate the length of the favorable season
to the species and the factors that might induce diapausing
egg production. At time, adults of the species
were reported to be active from February-March to
December (peaking in August-September) but most of
the eggs ceased to hatch since mid October. In the following
years, this 8-month full activity showed a constant
increase up to the winter 2003-04, when about
30% of the ovitraps of our monitoring network where
constantly egg-positive for the whole winter season.
Nevertheless, eggs laid between mid November and
mid February did not hatch up to the next March. Just