>> I tried feeding the observation hive...
>> but they were not interested in any syrup.

> Not taking feed is classic of nosema cerana.

Agreed.  
This is the simple answer, the one that fits the
list of symptoms described.

> All the comb is dry, with no brood, no stores 
> of pollen or honey.  

As resources became more limited, less brood
was raised.  If you would have video taped
the ob hive, you might have seen the queen
laying in cells that would later found to 
have no egg or larvae.  The bees would 
consume the eggs, knowing that there was
no incoming nectar or pollen to raise
brood.

> There are no dead bees in the hive.

One does have to wonder if a minimal set
of bees and the queen absconded at the
end of the process.  No brood to keep them
at home.

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