Förekomsten av mikrosporidien Nosema sp. hos honungsbin (Apis mellifera) i Sverige; : en jämförelse mellan fyra honungsbiraser under höst- och vintersäsong

Honey bees are fundamental for maintaining biodiversity in our ecosystems, but a recent decline in honey bee colonies has caused a growing concern for honey bee health worldwide. One component of colony collapses is Nosema (Microsporidia), which is associated with colony collapses in many subtropical regions. However, infection by Nosema is also known to accumulate within the honey bee hive during overwintering in colder climates. In this study, the prevalence of Nosema is compared between four honey bee subspecies during fall and winter and is focused on two hypotheses: 1) infection by Nosema is more prevalent in honey bees during winter and 2) infection by Nosema differs between different honey bee subspecies. Bees were dissected, and their guts were analysed for Nosema spores using a light microscope. Results showed a difference in amount of Nosema infected colonies between winter and fall. Also, results showed a difference between Buckfast bee (A. mellifera hybrid) and Carniolan bee (A. mellifera carnica) in Nosema infected colonies during the fall period. These results indicate that infection by Nosema in cold climates might be more prevalent than previously thought. Additionally, there might be differences in resilience between honey bee subspecies, but infection of Nosema seem to depend less on subspecies than season. More research is needed on Nosema in cold regions to assess the effect of Nosema on honey bees in Sweden and worldwide to prevent future colony collapses of honey bees