Jérémy Berret

Research Project

I am interested in the link between animal behaviour and infectious disease. In the case of vector-borne diseases for example, host choice behaviour of the arthropod vector drives the pathogen distribution in the vertebrate host population. Arthropod vectors often feed on multiple hosts that vary in their competence to harbour and transmit the pathogen. A good example is the western black-legged tick Ixodes pacificus, which is a vector of Lyme borreliosis (LB) in California. These ticks prefer to feed on lizards, which are non-competent hosts for the sprirochete bacteria that cause LB. This example shows how vector preference for pathogen-incompetent (or -competent) hosts can influence the epidemiology of vector-borne diseases.

For my Master project, I am interested in studying host choice behaviour of the sheep tick, Ixodes ricinus. Ixodes ricinus is the main vector of Lyme borreliosis in Western Europe. This widely distributed tick species is found on different vertebrate hosts in different places. In Switzerland, Scotland and Portugal, for example, I. ricinus ticks are often found on rodents & birds, birds but not rodents, and lizards, respectively. This geographic variation in host attachment could be due to (1) differences in host community, (2) differences in host preference, (3) or a combination of both. Recent population genetic studies on Ixodes ticks suggest the formation of genetically distinct races that prefer different reservoir hosts. The aim of my project is to use an experimental approach to test whether geographic variation in host attachment behaviour in I. ricinus reflects underlying differences in host preference.

I am currently establishing pathogen-free laboratory colonies of Ixodes ricinus that were sampled from Switzerland, Scotland and Portugal. We will measure tick host choice by using a host choice arena that gives ticks a choice among three types of vertebrate hosts: rodent, bird, and lizard, and an empty control chamber. We expect ticks to prefer the hosts on which they are most commonly found. We predict that Swiss ticks will choose both rodents and birds whereas Scottish and Portuguese ticks will prefer birds and lizards, respectively.