Know more

Our use of cookies

Cookies are a set of data stored on a user’s device when the user browses a web site. The data is in a file containing an ID number, the name of the server which deposited it and, in some cases, an expiry date. We use cookies to record information about your visit, language of preference, and other parameters on the site in order to optimise your next visit and make the site even more useful to you.

To improve your experience, we use cookies to store certain browsing information and provide secure navigation, and to collect statistics with a view to improve the site’s features. For a complete list of the cookies we use, download “Ghostery”, a free plug-in for browsers which can detect, and, in some cases, block cookies.

Ghostery is available here for free: https://www.ghostery.com/fr/products/

You can also visit the CNIL web site for instructions on how to configure your browser to manage cookie storage on your device.

In the case of third-party advertising cookies, you can also visit the following site: http://www.youronlinechoices.com/fr/controler-ses-cookies/, offered by digital advertising professionals within the European Digital Advertising Alliance (EDAA). From the site, you can deny or accept the cookies used by advertising professionals who are members.

It is also possible to block certain third-party cookies directly via publishers:

Cookie type

Means of blocking

Analytical and performance cookies

Realytics
Google Analytics
Spoteffects
Optimizely

Targeted advertising cookies

DoubleClick
Mediarithmics

The following types of cookies may be used on our websites:

Mandatory cookies

Functional cookies

Social media and advertising cookies

These cookies are needed to ensure the proper functioning of the site and cannot be disabled. They help ensure a secure connection and the basic availability of our website.

These cookies allow us to analyse site use in order to measure and optimise performance. They allow us to store your sign-in information and display the different components of our website in a more coherent way.

These cookies are used by advertising agencies such as Google and by social media sites such as LinkedIn and Facebook. Among other things, they allow pages to be shared on social media, the posting of comments, and the publication (on our site or elsewhere) of ads that reflect your centres of interest.

Our EZPublish content management system (CMS) uses CAS and PHP session cookies and the New Relic cookie for monitoring purposes (IP, response times).

These cookies are deleted at the end of the browsing session (when you log off or close your browser window)

Our EZPublish content management system (CMS) uses the XiTi cookie to measure traffic. Our service provider is AT Internet. This company stores data (IPs, date and time of access, length of the visit and pages viewed) for six months.

Our EZPublish content management system (CMS) does not use this type of cookie.

For more information about the cookies we use, contact INRA’s Data Protection Officer by email at cil-dpo@inra.fr or by post at:

INRA
24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu Logo Principal Oniris

Home page

Phylogeography of the tick Ixodes ricinus: strong genetic divergence between North African and European populations.

phylogeographie_de_la_tique_ixodes_ricinus
To fight ticks effectively (tick vaccines, acaricides), it is essential to know their genetic variability. We have shown that Eurasian populations of Ixodes ricinus have no genetic structure, whereas those in North Africa are very divergent. These populations could also present phenotypic differences, such as vectorial competence, which could have consequences on the epidemiology of some tick-borne diseases.

Context / challenges

Ticks are haematophagous mites capable of transmitting many diseases, both to humans (Lyme disease, tick-borne encephalitis...) and to animals (bovine piroplasmosis and anaplasmosis...). Worldwide, they are considered the second most important vector group after mosquitoes. In addition to these human and animal health issues, ticks and the diseases they transmit can be associated with environmental issues because of the important role of wildlife in tick gorgement but also as a reservoir of pathogens. In order to effectively control these vectors, for example by using tick vaccines or acaricidal products, it is essential to know their genetic variability. Ixodes ricinus is the most common tick species in Europe: its range covers most of the western Palearctic zone, from North Africa to southern Scandinavia, and from Ireland to the Caspian Sea. The objective of this study was to characterize the genetic variability of a large panel of populations covering the entire range of this tick by analyzing the nucleotide polymorphism of several genes and to describe the partitioning of this inter- and intra-population variability.

Results

We sampled 40 populations covering the entire range of Ixodes ricinus and sequenced 2 mitochondrial and 4 nuclear genes from 60 individuals. The genetic diversity observed is not structured according to the geographical origin of the samples. The diversity observed throughout Europe is similar to that observed in a single French population. Despite the low active dispersal capacities of these non-winged vectors, these results suggest the existence of significant gene flows between these populations, linked to the movements of wild (birds, deer...) or domestic (trade) hosts on which ticks remain fixed for several days (the time of their blood meal). Patterns of nucleotide diversity suggest that these populations are recently expanding. In contrast to what has been observed in European populations, ticks in North African populations - where ticks are confined to more humid mountainous areas - have been found to be genetically very different from all other populations in the Western Palearctic, indicating ancient genetic isolation.

Perspectives

This study is the first to highlight the existence of a strong genetic divergence of certain populations of I. ricinus within its range. Further studies are in progress to determine whether North African and European populations of this tick are interfertile (existence of pre- or post-copulatory reproductive isolation?). Experiments on the vectorial competence of these different tick populations for different pathogens will have to be carried out in order to find out whether these genetic differences also correspond to phenotypic differences that would have major consequences for the epidemiology of tick-borne diseases.

Partners

Pasteur Institute of Tunis (Professor Ali Bouattour)

Publications

  • Noureddine R., Chauvin A. et Plantard O. (2011). Lack of genetic structure among Eurasian populations of the tick Ixodes ricinus contrasts with marked divergence from north-African populations. International Journal for Parasitology 41. Pp 183-192.

Partners