Nosema ceranae and Lotmaria passim: partners in crime?

Nosema ceranae and Lotmaria passim are two commonly encountered eukaryotic parasites of the honey bee (Apis mellifera) digestive tract. In recent years, the microsporidian parasite N. ceranae has been shown to negatively impact the honey bee at both the individual and colony level, and is commonly cited by Canadian beekeepers as a factor contributing to winter colony mortality. Lotmaria passim is a recently characterized trypanosomatid parasite that is globally prevalent. Given the emergent nature of L. passim, little is known about how the parasite impacts its honey bee host. Unfortunately, even less is known regarding the impact mixed infections of N. ceranae and L. passim have on honey bees despite the prevalence of co-infections. Here we present data from some of our ongoing work where, using real-time (RT) PCR and hoarding cage bioassays, we follow the infection progress of L. passim in individually- inoculated bees over time, and investigate the impacts of both parasites (single and mixed infections) on honey bee mortality. Preliminary data suggest that L. passim does not significantly impact honey bee mortality, even at moderate to high doses (>5.0×105 promastigotes/bee). We will also describe the humoral defense responses of honey bees individually inoculated with one or both parasite species after short and prolonged exposure by quantifying antimicrobial peptide gene expression via RT-PCR. This study is the first to examine the pathological impacts of both N. ceranae and L. passim on the honey bee.