How EMF impacts sick bees: the effect of a 50 Hz electromagnetic field on the biochemical parameters of haemolymph in honeybee workers Apis mellifera infected with Vairimorpha ( Nosema ) ceranae

As a pollinator, the honeybee plays a vital role in the ecosystem, benefiting both humans and the environment. A major challenge in modern beekeeping is the loss of bee colonies, often caused by factors not fully understood, as the issues they face are complex and difficult to identify. It is now established that interactions between abiotic factors (e.g. pesticides, climate change, starvation, low-frequency electromagnetic fields) and biotic stressors (pathogens, parasites) significantly contribute to the loss of bee colonies, negatively affecting honeybee immune responses, metabolism and cognitive functions, among other aspects. This multifactorial nature is especially important in the context of nosemosis disease. Nosemosis type C, caused by infection with Vairimorpha ceranae, is one of the most common honeybee diseases and presents challenges due to its subtle symptoms and limited control options. The disease can persist in a colony for a long time without obvious signs. When an additional stressor occurs, it can work synergistically with V. ceranae infection, greatly increasing mortality. As a result, an infection that initially seemed harmless and invisible can quickly lead to the death of the entire bee colony. This study observed significant changes in biochemical markers, indicating that the factors studied affected honeybees at the cellular level. Exposure to a 50 Hz electromagnetic field (EMF) had unpredictable effects on infected bees, as the impacts of EMF and V. ceranae infection were not simply additive; sometimes, these factors appeared to interact antagonistically. In such cases, EMF tended to attenuate the effect of the infection, bringing the studied parameters closer to those in the uninfected control group. This pattern was evident in biochemical markers of haemolymph, such as alanine aminotransferase (ALT) activity and levels of creatinine and uric acid. The findings suggest that exposure to 50 Hz EMF may be significant for bees dealing with Vairimorpha ceranae infection.