>The current application protocol for fumagillin may exacerbate N. ceranae infection rather than suppress it.

> At lower fumagillin concentrations, significantly more infective N. ceranae spores were produced in treated bees than in untreated infected bees. Protein profiles of bees fed fumagillin confirmed our hypothesis that fumagillin affects bee physiology at concentrations that no longer suppress N. ceranae. Use of fumagillin may increase the prevalence of N. ceranae

> Fumagillin treatment is known to reduce microsporidian reproduction and is probably useful for protecting weak colonies [2], but the antibiotic may have unintended effects on the honey bee host, ultimately contributing to increased prevalence and pathogenicity of N. ceranae. Many variables could affect fumagillin concentration in hives post-treatment, including hive size, nectar flow and other factors. Current fumagillin application involves a treatment gap of 6 months or more and almost guarantees that the antibiotic will degrade to concentrations that allow release of the microsporidia and result in fast recovery of N. ceranae [2,8]. 

> In addition, the time period of N. ceranae hyperproliferation may reverse the benefits gained at the beginning of fumagillin treatment, resulting in indistinguishable performance between fumagillin treated and untreated hives [9]. Although field studies are necessary to determine if fumagillin use has value in specific situations, it is clear that new treatments for nosema disease are needed.  

Huang W-F, Solter LF, Yau PM, Imai BS (2013) Nosema ceranae Escapes Fumagillin Control in Honey Bees. PLoS Pathog 9(3): e1003185. doi:10.1371/ journal.ppat.1003185

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