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Sheep tick (Ixodes ricinus). © INRA, CHAUBET Bernard

Tick-fighting tactics

Ticks vector multiple pathogens

A recent study has shown that a large number of ticks are simultaneously infected with two or more pathogens. This study raises important new questions: can these pathogens also be co-transmitted to animals, including humans, and what are the consequences for human and animal health?

By Vayssier-Taussat Muriel, translated by Jessica Pearce
Updated on 06/20/2017
Published on 03/17/2016

Ticks are Europe’s number one arthropod vector of human and animal diseases. Ixodes ricinus can transmit a large number of bacteria, viruses, and protists. Little is known about the prevalence of co-infections, and the few studies addressing the topic have generally focused on just a handful of pathogens. Because co-infections could be more common than previously thought, INRA researchers decided to look at the prevalence of 38 known tick-borne pathogens, namely bacteria and protists, in Ixodes ricinus. They found that half of the ticks examined, which came from the Ardennes region of France, were carrying at least one pathogen. Among these infected ticks, 50% were co-infected, meaning they were carrying between two and five pathogens. Furthermore, since it is well established that ticks have natural endosymbionts that can affect pathogen transmission in arthropods, the researchers also simultaneously looked for symbiotic bacteria. They found that all the ticks examined were host to at least one type of endosymbiont.

This work underscores that co-infection in ticks is far more prevalent that previously imagined, a fact that could have major implications for human and animal health. For example, efforts must be made to develop new diagnostic tests better adapted to detecting tick-borne pathogens. Furthermore, the co-occurrence of symbionts and pathogens within ticks highlights the need to examine the possible interactions between the two groups and the consequences thereof. This information could then be used to develop novel, alternative strategies for controlling the transmission of tick-borne pathogens and the diseases they cause.

Scientific contact(s):

Associated Division(s):
Animal Health
Associated Centre(s):
Regional Board of Rhône-Alpes, Grand Est - Nancy, Occitanie-Montpellier, Jouy-en-Josas


Moutailler S, Valiente Moro C, Vaumourin E, Michelet L, Tran FH, Devillers E, et al. (2016) Co-infection of Ticks: The Rule Rather Than the Exception. PLoS Negl Trop Dis 10(3): e0004539. DOI: 10.1371/journal.pntd.0004539


This study was partially funded by the EU grant FP7-261504 EDENext and is catalogued by the EDENext Steering Committee as EDENext 421 (http://www.edenext.eu). This work was also supported by INRA's MEM Metaprogramme, the COST Action TD1303 (EurNegVec) and the CoVetLAb (ANSES, DTU, CVI, SVA, APHA). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.