On Sep 21, 2013, at 8:56 AM, randy oliver <[log in to unmask]>

 wrote:



> N apis appears to be more prevalent in colder climates.  But when I was

> speaking of cold, I was referring to seasonal cold, rather than the

> absolute value.



Genersch writes:

> While N. apis, the ‘classical’ Nosema-species infecting A. mellifera, is considered a rather benign honey bee pathogen rarely causing any colony losses, N. ceranae has been associated with or identified as causative agent of colony losses in some geographical regions leading to the assumption that N. ceranae is more virulent than N. apis (Higes et al., 2007). 



> However, reports on the virulence of N. ceranae for individual bees and for bee colonies are contradictory and several studies indicate an influence of climatic parameters like temperature on the virulence and assertiveness of N. ceranae



> The interpretation of the results of all these studies comparing the epidemiology and virulence of N. ceranae and N. apis rely on the correct identification of and differentiation between these two microsporidian species infecting A. mellifera.  



additionally, as far back as 2009:



> in Germany, involving about 220 honeybee colonies and a total of 1,997 samples collected from these colonies each spring and autumn and analyzed via species-specific PCR-restriction fragment length polymorphism (RFLP), are described. Statistical analysis of the data revealed no relation between colony mortality and detectable levels of infection with N. ceranae or N. apis. In addition, N. apis is still more prevalent than N. ceranae in the cohort of the German bee population that was analyzed. A possible explanation for these findings could be the marked decrease in spore germination that was observed after even a short exposure to low temperatures (+4°C) for N. ceranae only. 



> Reduced or inhibited N. ceranae spore germination at low temperatures should hamper the infectivity and spread of this pathogen in climatic regions characterized by a rather cold winter season.



More recent work:



> The honeybee pathogens Nosema ceranae and deformed wing virus (DWV) cause the collapse of honeybee colonies. Therefore, it is plausible that these two pathogens act synergistically to increase colony losses, since N. ceranae causes damage to the mid-gut epithelial ventricular cells and actively suppresses the honeybees' immune response, either of which could increase the virulence of viral pathogens within the bee. To test this hypothesis we exploited 322 Hawaiian honeybee colonies for which DWV prevalence and load is known. We determined via PCR that N. ceranae was present in 89–95% of these colonies, with no Nosema apis being detected. We found no significant difference in spore counts in colonies infected with DWV and those in which DWV was not detected, either on any of the four islands or across the entire honeybee population. Furthermore, no significant correlation between DWV loads (ΔCTlevels) and N. ceranae spore counts was found, so these two pathogens are not acting synergistically. 



> Although the Hawaiian honeybees have the highest known prevalence of N. ceranae in the world, with average number of spores been 2.7 million per bee, no acute Nosema related problems i.e. large-scale colony deaths, have been reported by Hawaiian beekeepers.







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