impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 121-123, 2008
Aedes albopictus in Rome: results and perspectives after 10
years of monitoring
F. Severini, M. Di Luca, L. Toma, R. Romi
Istituto Superiore di Sanità, Dip. M.I.P.I., Reparto di Malattie Trasmesse da Vettori e Sanità
Introduction
Abstract. In 1997, Aedes albopictus (Skuse 1894) was detected in Rome in two opposite areas of the city.
In the following 2 years, the species quickly spread. In 2000, scattered foci of the species were reported in
the whole urban area and in the outskirts of the capital city. In Rome, Ae. albopictus seems to have found
optimal environmental conditions to proliferate and to overwinter through and without diapausing eggs. In
ten years Ae. albopictus has colonized the whole urban area through three phases: first massive spread,
following maintenance of infestation, and colonization of alternative winter breeding sites with favorable climatic
conditions. Data collected during the 2007 show that rainfall is no longer the most important factor for
the development of the species, with respect to the past. In fact Ae. albopictus probably has found new
alternative larval breeding sites through the colonization of small water collections refilled periodically by
human activities. During 2007-2008 winter season, in order to evaluate the species adaptability, a study of
eggs hatching and length of larval cycle at low temperatures, was carried out in laboratory and in simulated
field conditions. Data and results are showed and discussed also by the light of existing literature.
Keywords: Rome, Aedes albopictus, monitoring, ovitraps, overwintering eggs
Since its discovery in Italy in 1990, the “tiger mosquito”
Ae. albopictus has spread quickly across the northern
and central regions of the country, causing considerable
concern among public health authorities. This species,
which easily colonizes container habitats in the peridomestic
environment, was accidentally introduced in
Italy by importation of used tires from USA. In 1997,
Ae. albopictus was first detected in Rome. In the following
years the species has spread more quickly from the
initial foci to 2 heavily populated suburbs of the town.
At present, scattered foci of Ae. albopictus are presents
throughout the whole urban area and in the majority of
the towns that belong to the province of Rome. In
Rome, the “tiger mosquito” seems to have found suitable
environmental conditions for proliferating and its
quick spread and establishment represent the 1st example
in Europe of extensive colonization of an urban area,
with involvement of hundreds of thousands people.
Founded by the City Council of Roma, and coordinated
by the Istituto Superiore di Sanità, a program of surveillance
and control was launched since 1998.
Materials and metods.
The monitoring was carried out yearly, with a network
of 650 ovitraps on the entire urban area (41.9°N Lat. -
Correspondence: Francesco Severini
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 4990 2301, Fax +39 06 4990 3561,
e-mail: francesco.severini@iss.it
12.4° Long. with about 350 km 2 of surface). The study
area was divided into about 300 zones, with a different
number of ovitraps (from 1 to 25), depending on the
extension and the features of each area. Black plastic
pots (500 ml capacity) were employed as ovitraps. A
strip of masonite ® (3x15 cm) was suspended vertically
in the middle of the pot to provide a suitable surface for
oviposition. Pots were filled with 350 ml of water. Every
week, pots were rinsed and refilled, strips were changed
and checked for egg presence. The number of eggs was
counted by observing the strips under a dissecting
microscope. In order to evaluate the distribution and
the abundance of the species in the study area, two
parameters were considered: 1) number of positive ovitraps
by total working ovitraps and 2) mean number of
eggs by positive ovitraps (Fig.1). Eggs number by positive
ovitraps was divided in 5 classes of abundance (1-
10; 11-50; 51-100; 101-300; more than 301 eggs). Data
were collected weekly, entered in a database (Microsoft
Access) besides to basic meteorological data (temperature,
relative humidity and mm of rainfall; fig. 2) and
analyzed using an adapted Arcview G.I.S software.
Fig. 1. Weekly rate of positive ovitraps for Aedes albopictus
and mean number of eggs/ovitrap recorded in Rome during
the 2007.