Nosema ceranae has infected Apis mellifera in Europe since at least 1998 and may be more virulent than Nosema apisRobert J. Paxtona, Julia Kleea, Seppo Korpelab and Ingemar Friesc
a School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK
b MTT Agrifood Research Finland, Plant Production, 31600 Jokioinen, Finland
c Department of Ecology, The Swedish Agricultural University, Box 7044, 75007 Uppsala, Sweden
(Received 13 March 2007 - Revised 4 September 2007 - Accepted 7 September 2007 - Published online 14 December 2007)
Abstract - Nosema ceranae, a microsporidian formerly regarded as confined to its Asiatic host Apis cerana, has recently been shown to parasitise Apis mellifera and to have spread throughout most of the world in the past few years. Using a temporal sequence of N = 28 Nosema isolates from Finland from 1986-2006, we now find (i) that N. ceranae has been present in Europe since at least 1998 and (ii) that it has increased in frequency across this time period relative to Nosema apis, possibly leading to higher mean spore loads per bee. We then present results of a single laboratory infection experiment in which we directly compare the virulence of N. apis with N. ceranae. Though lacking replication, our results suggest (iii) that both parasites build up to equal numbers per bee by day 14 post infection but that (iv) N. ceranae induces significantly higher mortality relative to N. apis.
Key words: Microsporidia / disease / exotic / emergent / PCR-RFLP
© INRA, DIB-AGIB, EDP Sciences 2007