Abstracts (first author)
Evasion or suppression? Infection strategies of a trypanosome gut parasite of bumblebees
Parasites can either avoid host detection (evasion) or actively suppress host immune responses (suppression) in order to infect their hosts. These two strategies could have important consequences for multiple infections. Evasion would not be beneficial in mixed infection if the co-infecting strain fails to also evade, but immune suppression would benefit both infecting strains irrespective of the other co-infecting strain’s strategy. Co-infection, in turn, provides the opportunity for both parasite competition and sexual recombination. The bumblebee Bombus terrestris is commonly infected by multiple strains of the trypanosome gut parasite Crithidia bombi in nature. We tested whether successful infection is achieved by suppressing or evading the host’s immune system by experimentally infecting workers of several colonies with Crithidia strains that were either highly or lowly infective. We used both single and mixed inocula of C. bombi clones, where mixed infections consisted of pairings between a highly and a lowly infective strain. We measured host gene expression of 27 candidate genes and quantified infection intensities within the same individual 18 hours post infection. We discuss implications and insights into the complex genetics of host-parasite interactions.