Abstract
Two species of Spiroplasma (Mollicutes) bacteria were isolated from and described as pathogens of the European honey bee, Apis mellifera, ∼30 years ago but recent information on them is lacking despite global concern to understand bee population declines. Here we provide a comprehensive survey for the prevalence of these two Spiroplasma species in current populations of honey bees using improved molecular diagnostic techniques to assay multiyear colony samples from North America (U.S.A.) and South America (Brazil). Significant annual and seasonal fluctuations of Spiroplasma apis and Spiroplasma melliferum prevalence in colonies from the U.S.A. (n = 616) and Brazil (n = 139) occurred during surveys from 2011 through 2013. Overall, 33% of U.S.A. colonies and 54% of Brazil colonies were infected by Spiroplasma spp., where S. melliferum predominated over S. apis in both countries (25% vs. 14% and 44% vs. 38% frequency, respectively). Colonies were co-infected by both species more frequently than expected in both countries and at a much higher rate in Brazil (52%) compared to the U.S.A. (16.5%). U.S.A. samples showed that both species were prevalent not only during spring, as expected from prior research, but also during other seasons. These findings demonstrate that the model of honey bee spiroplasmas as springtime-restricted pathogens needs to be broadened and their role as occasional pathogens considered in current contexts.
Highlights
Attempts to identify pathogens associated with unusually large numbers of moribund or dead worker honey bees Apis mellifera L. (Hymenoptera: Apidae) outside of colonies in the U.S.A. (Clark 1977) and France (Mouches et al 1982, 1984) revealed heavy loads of two species of cultivable bacteria within the class Mollicutes (Entomoplasmatales: Spiroplasmataceae) during hemolymph and gut tissue examinations from diseased bees
MicrobiologyOpen published by John Wiley & Sons Ltd
The multiyear variation in S. apis and S. melliferum we have shown here provides a congruous explanation for the disparate disease cycles observed in the past and support that these species may be unrecognized pathogens involved in modern disease cycles of honey bees that must be considered under the novel context of at least three newly emergent parasites not believed to be present at the time of original honey bee spiroplasma investigation: Nosema ceranae fungus, Varroa destructor mite, and Varroa Destructor Virus-1
Summary
Attempts to identify pathogens associated with unusually large numbers of moribund or dead worker honey bees Apis mellifera L. (Hymenoptera: Apidae) outside of colonies in the U.S.A. (Clark 1977) and France (Mouches et al 1982, 1984) revealed heavy loads of two species of cultivable bacteria within the class Mollicutes (Entomoplasmatales: Spiroplasmataceae) during hemolymph and gut tissue examinations from diseased bees. (Clark 1977) and France (Mouches et al 1982, 1984) revealed heavy loads of two species of cultivable bacteria within the class Mollicutes (Entomoplasmatales: Spiroplasmataceae) during hemolymph and gut tissue examinations from diseased bees. These bacteria tended to flourish in adult honey bees during spring vanish by summer from available serologic and microscopic detection, suggesting they opportunistically infected honey bee colonies between spring and summer via transmission from other hosts.
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