Sara Moutailler (1), Hélène Barré (2), Marie Vazeille (1), Anna-Bella Failloux (1)

1. Institut Pasteur, Génétique moléculaire des Bunyavirus, Paris, France
2. Laboratoire Parasites et Ecosystèmes Méditerranéens, Faculté des Sciences, Université de Corse, Corte, France

Tropical medicine & international health 2009, 14 (9): 1105-1109

Aedes albopictus has been established in Europe for some decades rendering temperate countries vulnerable to tropical diseases. The Italian chikungunya (CHIK) outbreak in the summer of 2007 demonstrated that indigenous transmission of CHIK was possible in Europe. To estimate the risk of a CHIK outbreak in Corsica, we assessed the vector competence of Ae. albopictus established in the island since 2006 towards a CHIK variant (E1-A226V). A dengue serotype 2 virus was also tested. Experimental infections showed that Ae. albopictus was highly competent to CHIK virus (disseminated infection rates ranging from 75% to 100%) and to a lesser extent, to dengue virus (12.5-68.8%). Moreover, Ae. albopictus ensured a high level of viral replication and was able to transmit the virus as early as 2 days after ingestion of infected blood with around 1 000 viral RNA available in salivary glands. The risk for a local transmission of CHIK is thus likely in Corsica, if other parameters determining the vector capacity of Ae. albopictus are suitable.

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VBORNET comment: 2009-11-27
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 that has been shown to be more easily transmitted by this species than the previous circulating virus strains (Schuffenecker et al., 2006, Vazeille et al., 2007). Results are not surprising as vector competence is genetically controlled (Hardy et al., 1983), even if it allows a certain variability of competence between populations. Populations of Corsica were more efficient than population from Alpes-Maritimes and much more than other indigenous mosquito species formerly tested (Vazeille et al., 2007). The virus title in salivary glands is high enough to ensure efficient release of infectious particles with saliva during a blood meal, as early as 2 days after viraemic blood ingestion. Aedes albopictus shows definitely a high potential of transmitting CHIK virus in Europe if entering in contact with viraemic hosts coming back from endemic areas. However, transmission will occur on the field only if other parameters of its biology such as density, longevity, host preferences, and duration of gonotrophic cycle are suitable.