Nosema ceranae infection alters honey bee (Apis mellifera) queen behavior and reproductive capacity

The Western honey bee (Apis mellifera) is crucial for agriculture, pollinating over 90 crops, 80% of flowering plants, and over 75 percent of fruits, nuts and vegetables. Therefore, maintaining their health is vital to biodiversity and our own food security. One of the main causes of poor honey bee health is infection by the microsporidian gut pathogen Nosema (recently named Vairomorpha) spp. Nosema weakens bees’ immune systems, reduces lifespan, causes dysentery, and impairs foraging, affecting colony health and productivity. Apis mellifera can be infected by two species, Nosema ceranae and N. apis. While the impact of N. ceranae on colony and worker health is well-studied, its effects on queen bee behavior remain unclear. This study examined the effects of N. ceranae infection on queen egg-laying rate, locomotion, and retinue size. We found that infection with N. ceranae caused a decrease in retinue behavior, but caused an increase in egg-laying capacity and speed. Understanding N. ceranae's impact on queen behavior is crucial, as queens are pivotal for colony productivity and task regulation. Identifying specific behavioral changes in queens caused by pathogen infection can help researchers and beekeepers better assess colony health and implement effective control measures against disease.