Inactivation of Nosema spp. with zinc phthalocyanine.

Most honey bee pathogens, such as Vairimorpha (Nosema), cannot be rapidly and definitively diagnosed in a natural setting, consequently there is typically the spread of these diseases through shared and re-use of beekeeping equipment. Furthermore, there are no viable treatment options available for Nosema spores to aid in managing the spread of this bee disease. We therefore aimed to develop a new method using novel Zinc Phthalocyanine (ZnPc) as a photosensitizer for the photodynamic inactivation of Nosema spores that could be used for the decontamination of beekeeping equipment. Nosema spores were propagated for in vitro testing using four caged Apis mellifera honey bees. The ZnPc treatment was characterized, encapsulated with a liposome, and then used as either a 10 or 100 µM treatment for the freshly harvested Nosema spores, for either a 30 and or 60-minute time period, under either light or dark conditions, in-vitro, in 96-well plates. In the dark treatment, after 30-min, the ZnPc 100 µM treatment, caused a 30 % Nosema mortality, while this increased to 80 % at the same concentration after the light treatment. The high rate of anti-spore effects, in a short period of time, supports the notion that this could be an effective treatment for managing honey bee Nosema infections in the future. Our results also suggest that the photo activation of the treatment could be applied in the field setting and this would increase the sterilization of beekeeping equipment against Nosema.