AUTHOR=Burnham Andre J. , De Jong Emily , Jones Jayre A. , Lehman Herman K. 

TITLE=North American Propolis Extracts From Upstate New York Decrease Nosema ceranae (Microsporidia) Spore Levels in Honey Bees (Apis mellifera)

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01719

DOI=10.3389/fmicb.2020.01719

ISSN=1664-302X

ABSTRACT=<p><italic>Nosema ceranae</italic> infections in honey bees (<italic>Apis mellifera</italic>) pose a severe threat to colony health. Beekeepers have used dicyclohexylammonium fumagillin to control <italic>Nosema apis</italic>, although it may be ineffective against <italic>N. ceranae</italic>. We investigated the ability of various propolis extracts collected from Upstate New York (United States) to decrease <italic>in vivo N. ceranae</italic> infection levels when fed <italic>ad libitum</italic> to <italic>N. ceranae</italic>-infected honey bees. Propolis extracts, most notably a dichloromethane extract, significantly lowered spore levels in a dose-dependent fashion 4 days post inoculation. When testing the <italic>in vitro</italic> anti-<italic>Nosema</italic> activity of propolis extracts, we report for the first time that spore viability was unaffected after a 24 h exposure to propolis extracts. These results present evidence that propolis extracts may effectively lower <italic>Microsporidia</italic> infections in honey bees, and that direct exposure of environmental spores to propolis alone does not kill <italic>N. ceranae</italic>.</p>