Abstract

Lotmaria passimcurrently appears to be the predominant trypanosome in honey bees worldwide. Although, the specific effects ofL. passimby single or mixed with other gut parasites such asNosema ceranaeon honey bees' health is still unclear. We consequently measured bees' survival, parasite loads, the expression of antimicrobial peptides (AMPs) and vitellogenin gene. Thus, (1) bees naturally infected withL. passim, (2) healthy bees inoculated withNosema ceranae, (3) bees naturally infected withL. passimand inoculated withN. ceranaeand (4) healthy bees (control) were maintained under controlled conditions. Honey bees infected withN. ceranaeor with mixed infections ofL. passimandN. ceranaehad significantly lower survival rates than the control group at 20 days post-inoculation (dpi). A competitive suppression was also detected, provided that theL. passimload was significantly affected by the presence ofN. ceranaeat 15 dpi. Expressions of the AMPs defensin and hymenoptaecin rapidly (two hours post-inoculation) increased in bees infected withN. ceranaeand mixed infections. However, this effect was not continuous. In fact, expressions of abaecin, defensin, hymenoptaecin and vitellogenin decreased drastically at 15 dpi in bees with both single and mixed infections. The decrease in the expression of AMPs and vitellogenin throughout this period was consistent with the reduced survivals observed in this study, indicating that mixed infections ofL. passimandN. ceranae, and even into a scenario of competition between them, may have a synergic effect on the survival and immune-related gene expressions (biomarkers) of worker bees.