On Fri, 23 Feb 2007 21:03:02 -0600, Peter Dillon <[log in to unmask]> wrote:
>Did N. ceranae pass to Apis mellifera from Apis cerana or, from Apis
>cerana to Apis mellifera?

Good question.  I wonder the same thing myself.  The short answer is that 
no one I have talked to knows for sure, but there is considerable 
speculation.  The long answer is below and is entirely derived from my 
reading of the following review on this subject:

Natural infections of Nosema ceranae in European honey bees.  I Fries, R 
Martín,A Meana, P García-Palencia,M Higes.  Journal of Apicultural 
Research 45(3): 230–233 (2006)

Nosema spores have been observed in A. mellifera and A. cerana (the small 
SE Asian honey bee) for a while now.  Up until recently no one knew very 
much about how many species of Nosema infected honey bees.  This is 
because it is difficult to differentiate Nosema species microscopically. 
As the review states:

"Many species of microsporidia cannot be distinguished using light 
microscopy and only with difficulty using electron microscopy (Larsson, 
1986; Rice, 2001) and it cannot be excluded that some earlier observations 
of microsporidia infections in A. cerana, and possibly also in A. 
mellifera, may in fact have been observations of N. ceranae".
 
In 2005 it was reported that N. ceranae was found in A. mellifera in 
Taiwan.  The report explains: "The apiary where the infection was detected 
had harboured both A. mellifera and A. cerana".  

The review continues: "Almost at the same time and following progressively 
increased incidences of problems with nosema disease in Spain diagnosis of 
honey bee diseases, confirmed for the first time in Europe N. ceranae in 
field samples of European honey bees(Higes et al., 2006)".

The authors conclude: "Using stored samples of microsporidian-infected in 
honey bees, it may be possible to trace the infection back in history, but 
we are unlikely to unravel all relevant details. The two parasite species 
may in fact have existed as parallel infections for a considerable amount 
of time. The increased detection of Nosema spores in honey bees in recent 
years with absence of typical signs associated with N. apis and the recent 
report of N. ceranae from Europe, suggests that there may be a link 
between these phenomena. However, research is needed before it can be 
established if N. ceranae has different effects on European honey bees 
compared to N. apis".

This is all that is known in print.  I expect the picture will become 
clearer soon, as several labs are actively working on this problem. 

Adony

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