tique Ioxides
22/02/2024 3 min

The first summary of French data on Ixodes ricinus ticks

ANSES financed and participated in a study reviewing the state of knowledge on the biology and ecology of Ixodes ricinus ticks and the pathogens they are capable of transmitting. By analysing data spanning a period of more than 60 years, this work provided an overview of current knowledge and highlighted the need to conduct further investigations and harmonise the surveillance methods used, to improve the control and prevention of this pathogen vector.

Ixodes ricinus ticks are one of the main vectors of pathogens in France. They can transmit the bacterium responsible for Lyme disease, as well as tick-borne encephalitis virus. As part of the national plan to combat Lyme disease and other tick-borne diseases, ANSES financed a study aimed at producing the first summary of research work carried out in France since the first studies on Ixodes ricinus ticks were undertaken in the 1960s. The current study, which took account of the results of 187 scientific publications, was conducted by the Alfort National Veterinary School.

Varying data depending on the département

The work involved mapping the distribution of these ticks in France and drawing up a list of the many pathogens they can carry. It also identified several knowledge gaps. “When we mapped the distribution of ticks in France, we found that ticks are mainly collected in areas close to research teams working on the topic. No studies have been carried out on the presence of ticks in certain départements, particularly in Provence-Alpes-Côte d'Azur and Centre-Val de Loire”, notes Johanna Fite, Project Officer for Vectors in ANSES’s Unit for the Assessment of Risks Associated with Animal Health, Welfare and Nutrition, and Vectors.

This finding also applies to certain pathogens: “For example, the occurrence of tick-borne encephalitis virus in nymphs and adult ticks has only been researched in four départements in North-East France, which is the geographical area where this virus has historically been present”, explains Elsa Quillery, Scientific Expert Appraisal Coordinator in the same unit. However, cases of this pathogen being transmitted to humans have occurred in other départements, suggesting that its geographical range is more extensive.

Some issues have been studied more than others

Moreover, the scientific literature has tended to focus more on certain topics: for example, among all the pathogens that can be transmitted by ticks, Borrelia burgdorferi – the bacterium that causes Lyme disease – has been the most widely studied. Studies on the animal hosts of Ixodes ricinus have mainly considered rodents and wild ungulates, such as deer, and have less often investigated other animal species, such as hares and reptiles, which can also be bitten by ticks and which, depending on the context, can play a role in the epidemiology of diseases.

The effects of the environment on larvae in different geographical areas, such as those with a Mediterranean or mountain climate, have also not been widely studied. And yet this knowledge is necessary to be able to better define the factors essential to the development of the species and to predict the risks associated with ticks, particularly in the context of climate change.

This study therefore showed that although a great deal of research on ticks has been carried out in France, there are still some gaps to be filled. “There are biases and limitations in our knowledge, and each laboratory or research project has its own collection and analysis methods, preventing the results from being compared. Establishing a national surveillance programme would help reduce these disparities, thereby optimising the prevention and control of tick-borne diseases”, concludes Elsa Quillery.

Find out more

Perez, Grégoire; Bournez, Laure; Boulanger, Nathalie; Fite, Johanna; Livoreil, Barbara; McCoy, Karen D.; Quillery, Elsa; René-Martellet, Magalie; Bonnet, Sarah I. The distribution, phenology, host range and pathogen prevalence of Ixodes ricinus in France: a systematic map and narrative review. Peer Community Journal, Volume 3 (2023), article no. e81. doi : 10.24072/pcjournal.291