>   and*N. apis*  could be present in these beehives without causing
> disease symptom and that there is no evidence for the replacement of*N. apis*  by *N.
> ceranae*, supporting the hypothesis that nosemosis is not the main
> reason of the collapse and death of beehives.

This study did not count how many spores per bee. Therefore, the top conclusion is misleading. It is important to know the level of nosema to determine the damage to bees. We might have differences about the economic  threshold which can vary based on geographical locations. Simply Nosema Kills bees and yes simply Nosema Kills bees.

Nosema has been known for a long time to be the silent killer of bees even before Varroa mites. Looking at 75 beekeeping operations (total 180,000 colonies) and testing 24 hives in spring and 24 hives in the fall per operation for 5 years (Total 18000 samples) showed that Nosema kills. In Alberta Canada we use 1 million spores per bee as our threshold.  Keeping in mind bees in Alberta can't defecate for 3-4 months a year during winter time. This can cause serious stress in case of nosema infections. As recent as winter 2011, I have 4 operations lost >75% of the bees NOT FOR VARROA BUT FOR NOSEMA. Two operations winter indoors and 2 operations winter outdoors. Testing bees in early spring from dying colonies,  levels of spores were as high as 18, 22 million/bee.
Nosema can be serious and yes it kill bees.  Bees in Spain can defecate all times and no stress! I wish that we winter our bees in Spain. Nice place to spend winter for bees and humans, too.

Medhat

Dr. Medhat Nasr
Alberta Provincial Apiculturist
Pest Surveillance Branch
Research and Innovation Division
Agriculture and Rural Development
17507 Fort Road NW
Edmonton, AB T5Y 6H3 Canada
Tel: 780-415-2314             Fax: 780-422- 6096
E-mail:  [log in to unmask]
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