Tuesday 23rd of May 2017

Nosema Tolerance

Today's microsporidian:  “nosema” is frequently misunderstood, even by experienced beekeepers. The confusion appears to stem from failure to recognize the difference between the 2 types of nosema, and the fact that they manifest themselves within the hive in entirely different ways.

Its older form, n. apis, is easily identified by the prevalence of fecal spotting and streaking around the entrance of the hive, and is readily visible on the combs and top bars. The newer strain of nosema, n. ceranae disrupts the life cycle of the bee in much the same way as n. apis, but it does not have any obvious symptoms.
It too is a fungus that invades the gut wall of the bee, inhibiting nutrient absorption, shortening the life of its host by weakening and leaving it more susceptible to other diseases and pathogens. But its presence can only be confirmed under microscopic examination. As a result, it can be missed as a primary cause of dwindling leading to colony collapse.
Our breeding program is founded on a hardy pioneer stock that was introduced over a century ago into Washington State's remote Olympic Peninsula. Their unmanaged survival within the fungus-rich environment of the world's largest temperate rainforest presented a unique opportunity for us to capture study and develop these feral swarms.
Because of our apiary's cool damp location we have continually tested and selected for queen breeding stock that demonstrates characteristics of nosema tolerance.
But when a series of environmental stressors converged on western Washington bringing the devastating effects from the arrival of nosema ceranae, our apiary was not spared.  Withholding chemicals to pursue a path of accelerated natural selection in conditions of extreme exposure to this new fungus was a high risk choice for us to make.
Committed to chemical free apiary management, our experience told us that decades of un-medicated exposure to nosema apis had resulted in successful adaptation.  Except for a single emergency application of fumagillin to stabilize our remaining colonies we decided to gamble on the prospect that our bees could develop a natural resistance to this new microsporidian as well.
Four disheartening years of 90% losses followed that decision.  So when the spring of 2012 arrived and only 10% of our colonies had failed, we were encouraged that achieving our goal of nosema tolerance was possible.
Later that year a Danish study was published that supports our belief. In part it concludes:
“…After decades of selective breeding for Nosema tolerance in the Danish strain, it appears these bees are tolerant to N. ceranae infections”.
Those long years of heavy winter losses  resulted in producing hardy un-medicated bees that continue to maintain healthy populations in spite of USDA Beltsville laboratory results confirming the presence of staggering n. ceranae spore loads...50 million spores per bee!
Since recovering from those extreme losses we have begun to identify another significant trait in our surviving colonies:  they have naturally adapted themselves to become extreme pollen hoarders
Because the importance of good nutrition cannot be overstated in the maintenance of healthy hives, we see this remarkable adaptation as integral to the successful survivability of our stock....see Better Fed Bees>
We are further gratified that our decision to withhold fumagillin proved to be even more fortuitous than we could have initially imagined.  Research by Dr. Huang et al points to the alarming effects of the practice of continuous feeding of that antibiotic  during commercial queen and package bee production which disrupts the microbial balance necessary to promote healthy honeybee digestive systems. "Nosema Ceranae Escapes Fumagillin Control In Honeybees"  states:
Protein profiles of bees fed fumagillin confirmed our hypothesis that fumagillin affects bee physiology at concentrations that no longer suppress N. ceranae.  Use of fumagillin may increase the prevalence of N. ceranae and is potentially a factor in replacement of N. apis by N. ceranae in US apiaries.
By carefully monitoring and selecting our breeder queens from this core group of survivors, we are confident that the regionally unique feral hybrid queen lines we are offering demonstrate genetics capable of withstanding many of the lethal pathogens that threaten honeybees everywhere.