Honey bee (Apis mellifera L.) colony losses are a recurrent problem worldwide for beekeepers and they have reached a very high incidence in the past few years. Pathogens seem to play an important role in most reports from different regions around the world over the last decade (Faucon et al., 2005; Higes et al., 2006; Martín-Hernández et al., 2007; Blanchard et al., 2008; Johnson et al., 2009; Neumann and Carreck, 2010). In April 2004 the beekeepers of the Groupement de Défense Sanitaire Apicole (GDSA) from the Jura Region, France, reported very heavy colony losses in their apiaries that had occurred during the previous winter. These losses were higher that those detected in any other year and they were confirmed in 10 apiaries visited by the GDSA inspectors. In this region, wild vegetation is the most representative flora, and crops such as maize or sunflower are not prominent. The symptoms detected in the affected colonies in the previous winter were similar to other clinical features provoked by Nosema ceranae infection, as described previously (Higes et al., 2008; 2009). Briefly, they included the disappearance of adult bees, unattended brood, reduced colony vigour (only a few bees surrounding the queen), no dead or trembling bees around the hives, and colony death. Nosema ceranae was detected in 64% of the samples, all of them from weakened or dead colonies, whereas N. apis or A. woodi were not detected in any colony (Table 1). All the positive N. ceranae samples were also positive for M. mellificae cysts and the Malpighian tubules developed lesions compatible with infection by this pathogen. Varroa destructor was present in 85% of samples, although the highest parasite ratio was only detected in the samples co-infected by N. ceranae. CBPV was the only virus detected in 10 samples, although only one colony developed symptoms compatible with this infection by this virus. In conclusion, clinical anamnesis, examination and laboratory analyses support the hypothesis that N. ceranae played a central role in these massive losses detected in the Jura Region, either alone or due to co-infection with other pathogens.
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