Nosema ceranae rebounds from fumagillin control

Fumagillin is the only approved antibiotic to control nosema disease in honey bees and has been extensively used in United States apiculture for more than 50 years. It is known to be toxic to mammals and must be applied periodically and with caution to avoid residues in honey. We show that the current application protocol for fumagillin may exacerbate microsporidia infection rather than suppress it, allowing hyperproliferation of the pathogens, particularly Nosema ceranae, when the drug is naturally degraded or diluted to low levels as occurs in hives over the spring and summer. Further investigations suggest that fumagillin continues to alter proteins in the honey bee midgut under very low dosages. N. ceranae is apparently released from the suppressive effects of fumagillin at dosages that continue to impact the bee midgut tissues, resulting in spore production that is significantly higher than in untreated bees.