# Evaluating the Efficacy of Common Treatments Used for _Vairimorpha_ (_Nosema_) spp. [PERSON]
## 4 Discussion  
Many consider the control of pathogens such as _Vairimorpha_ spp. essential for honey bee health [11] and important for reducing yearly honey bee colony losses. Our results provide weak or no evidence of any available registered or unregistered treatments to reduce _Vairimorpha_ spp. prevalence and intensity. Laboratory exposure of bees to _Vairimorpha_ spp. and subsequent treatment with various therapeutics showed no evidence of treatment effects on _Vairimorpha_ spp. spore prevalence or intensity (Experiment 1). Subsequent field experiments showed increased _Vairimorpha_ spp. intensity following exposure to HiveAlive(r) and Fumagilin-B (Experiment 2), weak short-term benefits of Fumagilin-B (Experiment 3),or no effects of treatments at all (Experiment 4). In all experiments, time was the principal factor that predicted _Vairimorpha_ spp. infection. Fumagilin-B, Honey-B-Healthy\({}^{\text{\textregistered}}\), and Nozevit treatments reduced the survival of bees when compared to that of bees fed only sugar water (the negative control group). We speculate that, in a colony setting, bees would likely interact with treatments mixed into supplemental sugar syrup differently than they would in the laboratory cage setting. In cages, for instance, honey bees are forced to feed on the provided treatments (no choice scenario), thus maximizing the treatment received per bee. In the field, however, honey bees would have access to ample pollen, honey, and nectar stores, in addition to supplemental sucrose. Therefore, caged bees (in a no choice/forced feeding scenario) might be exposed to higher amounts of treatment than bees in the field colonies, which could lead to reductions in honey bee survival. As for Fumagilin-B specifically, [12] reviewed negative effects of the compound on honey bee health and found fumagillin, along with its often overlooked counterion (dicyclohexylamine) in salt form, to be toxic to honey bees. More recently, researchers have found significant reductions in mortality following treatment with dicyclohexylamine in isolation; this counterion is present in fumagillin-DCH salt and in Fumagilin-B [32]. In the first field experiment (Experiment 2), bees treated with Fumagilin-B and HiveAlive\({}^{\text{\textregistered}}\) showed increased _Vairimorpha_ spp. intensity in April compared to that of bees in the negative control group. Previous studies have found that the death of beneficial gut bacteria resulting from exposure to antibiotics leads to increased vulnerability to _Vairimorpha_ spp. infection and antibiotic resistant pathogens in honey bees [33; 34; 35]. Given that the gut microbial communities of honey bees have high specificity and stability [34], it could take time for populations of beneficial microbes to rebuild post treatment, allowing opportunistic parasites to become established in the meantime. Thus, if antibiotic treatments become necessary, subsequent probiotic treatments and protein nutrition may also be essential to prevent establishment of parasites e.g., [36; 37; 38]. We hypothesize that this disruption of gut microbial communities led to higher _Vairimorpha_ spp. intensity in the treatment groups seen in this study. The _Vairimorpha_ species dominant in each experiment could influence the efficacy of the treatments used in these experiments. _Vairimorpha ceranae_ and _V. apis_ have been shown to differ in their respective biology and their impacts on honey bee colonies [10; 39; 40]. In Experiment 1, we confirmed _V. ceranae_ as the dominant species of _Vairimorpha_ via molecular detection. However, the species of _Vairimorpha_ was not confirmed in Experiment 2. Nevertheless, this experiment was performed between late 2017 and early 2018. At that time, _V. ceranae_ was the dominant species in honey bees throughout most of the world [40]. Experiments 3 and 4 were performed in early 2009 and from late 2009-early 2010, respectively. During these years, _V. ceranae_ was present but likely not the dominant species. There may have been a mix of _V. apis_ and _V.