Over the years I have had very good wintering results where most of my colonies would survive the winter and go on to be productive colonies. In 2017-18 I had my 1st winter losses that I traced back to the colonies being full of honeydew honey with very low glucose+frustose sugar levels (50g vs a typical 70 to 75g per 100g). This also told me that the honey contained much more material that the bees would not be able to digest (complex sugars and "ash"). The energy output would also be lower requiring the bees to consume more to get the same energy output than an average honey. This explained the excessive dysentery observed in the failed colonies. Nosema c is also known to be an energy robbing disease that exacerbated this problem. Defecating inside of the hives likely also spread the infection (Nosema c + Amoeba). At the time, I was not familiar with Amoeba disease which I later learned to identify using microscopy and basic bee dissection.
Nosema in combination with Amoeba disease has been my main source of winter colony failures. Initially, prior to me noticing the amoeba "globes" in my winter bee feces I would notice very high Nosema c counts in my struggling colonies. However, even healthy colonies would sometimes have bees with very high Nosema spore counts. The only difference between healthy and struggling colonies was the hive front bee mortality.
Last year, I decided to determine what the observed globes were that I was observing in the dead bees from the colonies with high mortality. I first taught myself to dissect out the bees digestive tract (mid & hind gut and the malpighian tubules). https://youtu.be/6QFAjMBtBvI
I reached out to Dr Ellis from the University of Florida who put me in touch with one of his PhD students Dr Iredale who helped ran some DNA tests using a newly released PCR protocol from Germany and did further analysis on my sick bees. The test confirmed my diagnosis.
What is Amoeba Disease? Also known as Malpighamoeba mellificae
Malpighamoeba mellificae is a single celled parasite which affects excretory organs (malphigian tubules) of adult bees, causing the contagious disease called amoebiasis, which ultimately leads to death of the host.Worker bees are most prone to being infected. It is commonly found in collaboration with nosemosis. In order to diagnose the 3 - 15 μm size parasite, removal of the malphigian tubule is necessary. Because of there being no viable treatment against this parasite, preventional measures such as providing a clean food supply for the hive are crucial.
Hive front bee mortality during winter. Increases during cold snaps < -30C.
Bees die in a spasm at hive front.
Microscopy checks of these dead bees typically have high Nosema counts and the presence of Amoeba cysts in the feces.
Dissecting individual bees and observing malpighian tubules will show them severely infected with cysts
Severe dysentery was only observed with the presence of honeydew honey in colony. Some minor feces however is present.
Note: Frame and hive equipment feces was tested. It all showed a high concentration of Nosema spores and Amoeba cysts.
Infection History and Probable Transmission
I keep very good notes and activvely share my observations and findings on our shared north of 60 beekeeping group on Facebook. I was able to look back in my notes to track and look back at some of my older microscopy images to observe Amoeba cysts and trace back the likely infection transmission sequences. (Document link)