Activation of host constitutive immune defence by an intestinal trypanosome parasite of bumble bees

Abstract

However, recently it has become apparent that gut infections may interact with the host immune system in more complex ways. Here, using bumble bees, Bombus terrestris and their non-invasive gut trypanosome, Crithidia bombi, as a model system we investigated the effects of parasitic infection, host resources and the duration of infections on the host immune system. We found that infection doubled standing levels of immune defence in the haemolymph (the constitutive proPhenoloxidase system), which is used as a first, general defence against parasites.However, the physical separation of the parasite from the haemolymph suggests the presence of a messenger system between the gut and the genes that control the proPhenoloxidase system. Surprisingly, we found no direct effect of 10 15 host resourcestress or duration of the infection on the immune system. Our results suggest a novel and tactical response of insects to gut infections, demonstrating the complexity of such host-parasite systems. 20

Bumble-bee foragers infected by a gut parasite have an impaired ability to utilize floral information

“…Our data suggest that infection by C. bombi could reduce colony success by impairing the ability of foragers to monitor and acquire floral resources. Moreover, although C. bombi is considered to be a benign parasite, food stress increases mortality in infected individuals (Brown et al 2000(Brown et al , 2003a. Thus, the reductions in resource acquisition by infected foragers could also have detrimental effects on colony success by increasing mortality levels in infected nest bees.…”

Antimicrobial peptides play a functional role in bumblebee anti-trypanosome defense

“…C. bombi prevalence in B. terrestris populations ranges from 10-30% but can be much higher (80%) (Shykoff and Schmid-Hempel, 1991) with increased inter-colony transmission as the season progresses (Imhoof and Schmid-Hempel, 1999). A variety of fitness effects are seen at the colony level due to infection: queens have reduced success in colony founding (Brown et al, 2003), colonies have smaller worker populations and produce fewer sexual offspring (Brown et al, 2000), and the ability to learn floral cues is impaired in infected workers (Gegear et al, 2006). The virulence (i.e.…”

Adult honeybees (Apis mellifera L.) abandon hemocytic, but not phenoloxidase-based immunity

“…Cellular immune reactions and prophenoloxidase (proPO) activation are launched immediately after an infection is detected and are responsible for clearing most infecting microbial challengers from insect circulation within the first hours (Dunn and Drake, 1983). Both reactions make up the insects' constitutive immune system, which is present at any post-embryonic life stage without previous infection (Brown et al, 2003).…”