High-Level Resistance of Nosema ceranae , a Parasite of the Honeybee, to Temperature and Desiccation

Abstract

Resistance of Nosema ceranae to different exposure conditions has been evaluated by using Sytox green and DAPI (4,6-diamidino-2-phenylindole) to test spore viability. High thermotolerance at 60 and 35°C and resistance to desiccation were observed. However, a significant decrease in viability after freezing and a rapid degeneration of spores maintained at 4°C were also detected.Two Nosema species have been related to pathology in the honeybee: Nosema apis (18) a parasite of Apis mellifera, the western honeybee, and Nosema ceranae (4), a parasite of Apis cerana, the eastern honeybee. Currently, however, N. ceranae is considered an emergent and important parasite of Apis mellifera (4).Over the last few years, an increase in infections by this microsporidian has been detected in several European countries, together with an increase in honeybee colony deaths and a consequent decrease in the production of honey (9). However, it is not clear if N. ceranae infection may be the only factor related to this disorder, since this pathogen has also been found in healthy colonies (14). In Spain, Higes et al. (7,9) have demonstrated the presence of this parasite in honeybee samples from colonies with clear signs of population depletion, relating the colony collapse disorder to N. ceranae. The presence of this microsporidian is not exclusive to Europe, since it has also been described in bee samples collected about a decade ago in the United States (3).The pathology produced by N. ceranae in A. mellifera bees may be higher than that produced by N. apis, showing a rapid autoinfective capacity of the spores to spread the infection among epithelial cells, producing high mortality (6). On the other hand, reduced longevity of caged N. ceranae-infected worker bees compared to bees infected by N. apis has also been found (15).To date, continuous cultures of N. ceranae are not available and there is no effective treatment. For this reason, it is important to study the effects of different exposure conditions, such as time, temperature, and desiccation, on the viability of spores kept in the laboratory for use in the search for new treatments and for development of culture protocols. In addition, as different levels of thermotolerance in the environment and different epidemiological patterns have been described for these microsporidia, available data on resistance of N. apis spores cannot be extrapolated to N. ceranae.Spores. Spores from N. apis and N. ceranae were provided by the experimental apiary of the Regional Apicultural Center in Marchamalo, Spain. Recently collected spores were purified as described previously (8). The spore concentration was determined by counting with a hematocytometer chamber. Two stocks of N. ceranae spores were used (S1 and S2). All studies were carried out at a concentration of 5 ϫ 10 5 spores/ml. The Nosema species was determined by multiplex PCR, which amplifies the 16S rRNA locus (12).Spore treatments. The effects of time, temperature, and desiccation on viability were measured at different points. All ...

Five-Year Cohort Study of Nosema spp. in Germany: Does Climate Shape Virulence and Assertiveness of Nosema ceranae ?

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A Comparative Study of Environmental Conditions, Bee Management and the Epidemiological Situation in Apiaries Varying in the Level of Colony Losses

“…The development of N. ceranae is highly determined by the temperature. This species is less resistant to low temperatures than N. apis (Fenoy et al, 2009;Fries, 2010;Gisder et al, 2010;Chen et al, 2012). Considering this fact, we expected the distribution of N. ceranae in our climate to be similar to those levels identified for cooler regions Forsgren and Fries, 2013;Meixner et al, 2014).…”

Prevalence of Nosema species in a feral honey bee population: a 20-year survey

“…A recent study tested the survival capability of N. ceranae in different extreme temperature and desiccation settings (Fenoy et al 2009). The authors found that compared to control spores that were kept at 4°C, about 90 % of N .ceranae spores heated at 60°C for 6 h remained viable.…”