“Evolution and manipulation of vector host choice”
Sylvain Gandon (July 2018)
A new theoretical framework to study the epidemiology, the evolution and the manipulation of vector host choice behavior
Imagine you are a female mosquito. You are the vector of a pathogen that infects a vertebrate host you feed upon. You have the choice between feeding on an uninfected host or on a host infected by this pathogen. Which host should you pick for your next blood meal? Now, imagine that you are the pathogen. You have the potential to modify the preference of the female mosquito by modifying the scent of the infected host, but also, more directly, by modifying the decision of mosquitoes once they become infected. What should you do?
Answering these questions and understanding the evolution host preference is key for the epidemiology of vector-borne diseases. A growing number of experimental studies are revealing the diversity of behavioral preference of vector species from a broad range of pathosystems. In this paper, Sylvain Gandon develops a theoretical framework to study the evolution and the manipulation of vector behavior. This analysis shows that many factors are acting on the evolution of these traits: the fitness costs of the infection, the prevalence of the infection in the different hosts, whether or not the female mosquito is already infected, whether the pathogen manipulating the mosquito is currently infecting the mosquito or the vertebrate host. The model yields multiple evolutionary outcomes and explains the diversity of host choice behaviors observed in different vector-borne diseases. In particular, this analysis helps understand why several pathogens have evolved manipulation strategies that vary with the infectious status of their vector species, while other pathogens seem unable to evolve such complex conditional strategies.
The transmission of many animal and plant diseases relies on the behavior of arthropod vectors. In particular, the specific preference for infected or uninfected hosts observed in many vector species is expected to affect the circulation of vector-borne diseases. Here I develop a theoretical framework to study the epidemiology and the evolution of the manipulation of host choice behavior of vectors. I show that vector preference strategies have dramatic epidemiological consequences. I also explore the evolution of vector host choice under different scenarios regarding the control of the vector behavior by the pathogen. This analysis yields multiple evolutionary outcomes and explains the diversity of host choice behaviors observed in a broad range of vector-borne diseases. In particular, this analysis helps understand why several pathogens have evolved manipulation strategies that vary with the infectious status of their vector species while other pathogens seem unable to evolve such complex conditional strategies. I argue that contrasting the behavior of infected and uninfected vectors is key to reveal mechanistic constraints acting on the evolution of the manipulation of vector behavior.