Evaluating Efficacy of Fumagilin-B^® Against Nosemosis and Tracking Seasonal Trends of Nosema spp. in Nova Scotia Honey Bee Colonies

Abstract

The efficacy of the antimicrobial Fumagilin-B® against nosemosis was evaluated in both spring and autumn feeding treatments following label directions in seventy-two honey bee (Apis mellifera) colonies across three apiaries in Nova Scotia, Canada. The seasonal trend of Nosema spp. spore loads was also tracked in these same colonies throughout a thirteen-month period (February 2018 – March 2019). We found the spring Fumagilin-B® treatment to be effective at significantly suppressing Nosema spp. spore levels below the recommended treatment threshold. There was no effect of Fumagilin-B® treatment in the autumn based on low spore levels at this time. We detected a drastic increase in Nosema spp. spore loads as May progressed but a decline in spores in summer (June–September). By October, there was another increase in spore levels, but this increase did not exceed the economic treatment threshold. Across seventeen collection periods in both control and Fumagilin-B® colonies, 74% (25) of samples tested positive for Nosema ceranae, while 26% (9) contained no Nosema spp. spores. No Nosema apis spores were detected during this trial. Our results indicate that Fumagilin-B® is an effective management practice in the spring, but colonies should still be monitored in the autumn. Our data also support that the Nosema species profile is shifting to be exclusively N. ceranae and the treatment threshold for Fumagilin-B® may need to be updated to reflect this, as the threshold was originally developed for N. apis.

Potential of Fumagillin and Agaricus blazei Mushroom Extract to Reduce Nosema ceranae in Honey Bees

“…On day 9, and at the end of the experiment (on day 15), the highest spore load was in the infected but not treated (I) group as compared to the treated group ( Figure 3 ), indicating the anti- Nosema effect of the applied treatments. For fumagillin, the highest spore number (excluding the I group) was in the group treated from day 6 (I-F6), and the lowest was in the group treated from day 1 (I-F1), which proves the direct relation between fumagillin treatment and the number of Nosema spores, confirming the known anti- Nosema effect of fumagillin [ 3 , 28 , 45 , 57 , 85 , 86 , 87 ].…”

“…Moreover, fumagillin showed a beneficial effect in terms of reducing some negative effects of Nosema infection (by decreasing Nosema loads and consequently preventing Nosema -induced immune suppression and oxidative stress). Bearing in mind the observed negative effects of fumagillin and the absence of registered fumagillin formulations in Europe [ 45 , 46 ], it is justified to look for a natural alternative for Nosema control. The positive protective effect of completely natural A. blazei extract proven in this research shows potential in combatting Nosema and deserves to be further investigated.…”

“…It is available in a few commercial formulations (Fumagilin-B, Fumidil B, Fumagilin DCH, etc.) registered in the USA [ 44 ], Canada [ 45 ] and Argentina [ 46 ], while there are no registered formulations in Europe [ 46 ]. Due to severe bee losses and the high prevalence of N. ceranae in several European countries: United Kingdom, Spain, Belgium, Greece, Hungary, Romania, etc., provisional approvals were obtained for the use of fumagillin under veterinary supervision for the treatment of Nosema -positive colonies [ 44 ].…”

Effects of Agaricus bisporus Mushroom Extract on Honey Bees Infected with Nosema ceranae

“…Greater stimulation of gene expression in group I-Abs1 and I-Abs3 compared to I-Abs6 indicates better efficacy of the extract before and at the moment of infection with N. ceranae. A better protective effect is expected as the extract is rich in polysaccharides [5,[36][37][38], while the anti-Nosema effect is more typical for antibiotics such as fumagillin [5,29,30,[33][34][35]. Moreover, we used crude water extract which, besides polysaccharides (almost 70%), contains proteins (5.31%) and phenolic compounds (2.7%) as well [71,81].…”

“…The control of nosemosis includes a wide range of beekeeping practices [3] and application of chemicals, such as fumagillin, an antibiotic derived from the fungus Aspergillus fumigatus [26,27]. Although fumagillin use is prohibited in most of European countries due to risk of its commercial formulations (Fumagilin-B, Fumidil-B,) to leave residues in bee products [28][29][30], to affect food safety [31,32], and to increase bee mortality [30], however, it is still licensed in the United States [33], Canada [34], and Argentina [35]. Moreover, its effectiveness has been questioned [28], imposing a constant effort of scientists to discover alternative substances, which would be effective against Nosema spp.…”