In the past decade, Aedes albopictus has been making steady northward progress from the Mediterranean coast into Europe. A highly opportunistic breeder, Aedes albopictus will lay eggs in almost any natural or artificial container-anything that holds water. They’re also attracted to dark areas, which often leads to the mosquitoes hiding in containers and being transported along with cargo or passengers on major highways.
As a vector for both dengue and chikungunya, Aedes albopictus is an increasingly challenging threat for public health professionals, especially when local transmission of these diseases begins.
When Remí Foussadier joined the Entente Interdépartementale de démoustication (EID) Rhone-Alpes in 2001, the primary concern was managing the Aedes vexans population from a nuisance perspective. With three million residents and an area of approximately 2,000 square kilometers, the district comprises a mix of urban and rural habitats-including up to 200 square kilometers of wetlands. “When I first started, Aedes albopictus wasn’t a concern,” said Remí. “Around 2004, we began seeing them in the south of France and along the Mediterranean coast. Now they’ve been identified here in central regions and farther up the Atlantic coast. And the introduction of this invasive species has required us to shift our surveillance and control strategies.”
MONITORING LOCAL TRANSMISSIONS
As Aedes albopictus has moved north, local cases of both dengue and chikungunya have occurred (both dengue and chikungunya are mandatorily notifiable diseases in France).
In October 2013, a laboratory technician at the French National Reference Laboratory of arboviruses in Bouches-du-Rhône was diagnosed with an autochthonous case of dengue fever.1 Extensive laboratory testing ruled out occupational exposure. One year later, health officials in the Provence-Alpes-Cote d’Azur (PACA) region reported four additional cases between August and October.2 These cases were from Aubagne, Var, Toulon and Bouches-du-Rhône.
As of September 17, 2015, authorities had reported six confirmed and one probable case of locally acquired dengue.3
Chikungunya has followed a similar pattern over a similar time frame. In October 2014, 12 autochthonous cases of chikungunya were reported in a district of Montpellier, traced back to a single resident of the district who had just returned from Cameroon. This was the first significant outbreak in Europe since the epidemic in Italy in 2007 (which was due to an east central South African strain).4
SHARING THE LATEST INTELLIGENCE
To help combat the spread of Aedes albopictus and its pathogens, districts throughout France are in constant communication. “We’re working together with districts in the south and throughout the EU to refine our strategies year after year, depending on where Aedes albopictus are breeding,” said Remí. One of the biggest changes his district has encountered in dealing with Aedes albopictus is the need to work in more populated areas to conduct surveillance and control operations. “We’ve had to greatly expand our communications and community outreach since we’re working in more densely populated areas. You have to balance people’s concerns of environmental or human impact with their need to be safe from disease.”
With regulations restricting the use of wide-area aerial applications, Remí’s team is working on adapting a terrestrial approach in urban areas using trucks and backpack equipment for their larviciding and adulticiding efforts. “We’re constantly refining our efforts, not only to stay ahead of the insects and the spread of the pathogens, but also to keep the public educated and help break the transmission cycle,”he said.
1 Marchand E, et al. Autochthonous case of dengue in France,October 2013. Euro Surveill. 2013;18(50):pii=20661.
Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20661
4 Delisle E, et al. Chikungunya outbreak in Montpellier, France, September to October 2014. Euro Surveill. 2015;20(17):pii=21108. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=21108