A. Talbalaghi [1], S. Moutailler [2], M. Vazeille [2] and A.-B. Failloux [2]

Medical and Veterinary Entomology 2010; 24(1):83-87; Doi : 10.1111/j.1365-2915.2009.00853.

The Asian tiger mosquito Aedes albopictus (Skuse) (Diptera: Culicidae), native to Southeast Asia, has extended its geographical distribution to invade new temperate and tropical regions. This species was introduced in 1990 to Italy and has since become the main pest in urban settings. It was incriminated as a principal vector in the first European outbreak of chikungunya virus (CHIKV) in the province of Ravenna (Italy) in 2007. This outbreak was associated with CHIKV E1-226V, efficiently transmitted by Ae. albopictus. The occurrence of this outbreak in a temperate country led us to estimate the potential of Ae. albopictus to transmit CHIKV and dengue virus (DENV), and to determine the susceptibility to CHIKV of other mosquito species collected in northern Italy. Experimental infections showed that Ae. albopictus exhibited high disseminated infection rates for CHIKV (75.0% in Alessandria; 90.3% in San Lazzaro) and low disseminated infection rates for DENV-2 (14.3% in San Lazzaro; 38.5% in Alessandria). Moreover, Ae. albopictus was able to attain a high level of viral replication, with CHIKV detectable in the salivary glands at day 2 after infection. In addition, the other three mosquito species, Anopheles maculipennis Meigen, Aedes vexans vexans (Meigen) and Culex pipiens L., showed variable susceptibilities to infection with CHIKV, of 0%, 7.7% and 0–33%, respectively. This information on vector competence is crucial in assessing the risk for an outbreak of CHIKV or DENV in Italy.

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VBORNET comment: 2010-02-24
This paper completes the assessment of the vector competence of the Ae. albopictus populations spreading in Europe. The studied populations show high competence for CHIK virus infection for a variant isolated from a patient in La Reunion island, and phylogenetically close related to the isolates of the Italian strain. CHIKV was detectable in the salivary glands from 2 days after the ingestion of an infectious bloodmeal which support previous data (Vazeille et al., 2007, 2008; Moutailler et al., 2009) and highlights the risk of a rapid spread of an infection. Other tested species were no or less susceptible to CHIKV, but curiously for the first time a strain of Culex pipiens show a certain susceptibility, contrarily to those from southern France (Vazeille et al., 2008). Once more, Ae. albopictus shows a high potential of transmitting CHIK virus, and also a potential albeit lower to transmit DEN virus. Therefore surveillance of viraemic humans coming back from endemic areas appears relevant, particularly in areas where vector density and longevity are high.

References:

1. Mosquito Control District of Alessandria, Bologna, Italy 
2. Génétique Moléculaire des Bunyavirus, Institut Pasteur, Paris, France