Northern Nosema Monitoring
What is Nosema? Source: BeeAware
Nosemosis, or Nosema disease, is caused by two species of microsporidian parasites (a type of spore forming fungus) called Nosema apis and Nosema ceranae. N. apis is thought to have originated on European honey bees, while N. ceranae is thought to have evolved as a pest of Asian honey bees (Apis cerana) and has only started to affect the European honey bees relatively recently. N. ceranae appears to be more damaging than N. apis, affecting more cells in the bees mid-gut and killing infected bees faster than N. apis.
Infection of adult bees at a young age can cause the bee to have difficulty digesting food for the rest of its life. These bees usually do not produce brood food/royal jelly secretions from the hypopharyngeal glands and often skip the brood rearing stage of their life, becoming forager bees at a young age. The infected bee often has a shortened adult lifespan. When queen bees become infected they also have reduced lifespans and cease to lay eggs. These impacts cause reduced colony health, population and performance, which can ultimately result in the colony dying.
Both species of Nosema infect worker bees, queen bees and drones. The fungi produce spores which are ingested by adult honey bees when they feed on food and water contaminated with spores, or are picked up while cleaning contaminated combs, robbing contaminated hives or by infected bees drifting to new hives. A single spore can cause infection, and by the time that infection is fully developed in an adult bee, there could be between 30-50 million spores in the gut of the bee. The life cycle of both Nosema species are similar and consist of the following:
- Infection begins when a bee ingests Nosema spores, which then germinate inside the mid-gut of the bee.
- The fungus enters the cells of the mid-gut and begins to absorb nutrients. This causes the cell to become damaged and the bee to be more susceptible to secondary infections.
- The fungus grows and multiplies infesting more of the mid-gut cells and produces spores.
- Several million spores can be produced in a single worker. The spores either germinate within the bee’s mid-gut, infecting new cells, or pass through the bee’s digestive system.
- Faecal material containing Nosema spores can contaminate food and water sources, where they can then be ingested by other bees. Spores can also be spread to non-infected bees when they clean contaminated combs, or rob contaminated hives and ingest spores in the process.
Example of Nosema symptoms:
Dysentery is not a symptom of Nosema but a mechanism of Nosema transmission from a sick bee to healthy ones in the hive when we don’t have cleansing flights for 4-5 months... Some honeys may increase the risk of dysentery (e.g. Honeydew honey is high in ash content so bees fill up quickly on it and then have to defecate in the hive) thus potentially exposing other bees to Nosema if the pooping bee is infected... once Nosema takes hold bees need to eat more to get the same energy output thus increasing the defecation in the hive. Add a week of -40C and the cycle speeds up. That’s why I am moving away from top entrances due to the magnitude of heat loss through it in my cold climate. Several studies have shown better overwintering when bees were fed 2:1 sugar syrup as part of the winter preparation. Bees are better able to go longer periods in between cleansing flights. Stay away from organic or any "brown" sugars as they contain more impurities. Stick with pure white sugar!!
Picture on right was after -40C morning
•Dead bees in the 1000s likely due to dark honey left in hive causing severe dysentery and bees flying out to defecate and dying after hitting cold air.
•Nosema (bee disease) was found after randomly sampling these bees
Dysentery – I can’t hold it in anymore
(This was a perfectly healthy hive before winter – 3rd winter)
Since bees can only retain about 30 to 40 percent of their body weight in fecal matter, when the time between cleansing flights is too long, they will void inside the hive or just outside of it. This is what we call dysentery.
This re-enforces the importance of feeding 2:1 sugar syrup as part of your winter preparation.
Bees are maintaining a very high hive temperature (>30C) with a lot of fluctuation.
Testing for Nosema
You can send a dead bee sample to the National Bee Diagnostic Centre or purchase / borrow someones microscope.
To get a basic Positive/Negative result
- Collect 10 random bees (dead or alive) and place them in a small ziplock
- Crush them with a hard round object (empty glass jar)
- Add 1ml of distilled water per bee
- Blend solution with your hand by squishing ziplock bag throughout dead bees
- Use plastic spoon to collect several drops of liquid and place on clean slide, add top cover
- At X400 look at slide through your microscope
Visit Randy Oliver's Scientific Beekeeping for detailed approach
Here is a YouTube video of Randy Oliver demonstrating the simple test procedure
Figure Below: Example of a hive with a very high Nosema infection with a obvious signs of HDE (aka Cattails and Fried Eggs spores). Bees infected with Nosema will consume higher amounts of winter stores. (Picture of Bee guts under at x400). This hive was installed in equipment from a previous dead out (Nosema/Dysentery). The hive was disinfected, frames were sprayed with peroxide solution and sun baked for 3 days per side. It is likely the new colony got infected through infected parts. 3 other similar hives (installed in dead out equipment) show no signs of infection. Lab results for below hive confirmed Nosema Ceranae with a count of 21M.
Picture Below: (2018) shows winter mortality rate of infected hive (left) vs non infected hive (right). Sick hive consumed most of its winter reserves as well as its candy board. Normal hive still had plenty of stores and hadn't touched its candy board. Moisture levels are also much lower than sick hive. Spring bee mortality of an infected hive is very high once the bees re-initiate there foraging activities. The hive to the left survived until May 15. In early April this hive had 12-14 frames of bees. I soon discovered that the queen did not survive the winter. I attempted to re-queen but she soon became sick (lethargic) and died. Most of the bees were dead by early May. I sampled some of the last surviving bees and tested them for Nosema C (picture to right). They all came back with very high counts (based on my standard sampling approach).
Winter Testing (Dead Bees at Front of Hive)
Here is my ranking approach. In a lab setting I would do more individual bee crushes x 10 per hive to understand infection rates, maybe some day. My #3 on mortality is a bit lite on dead bees (I couldn't find a good picture).
This ranking gives you an idea of Nosema spore concentration. It is important to always follow the same sampling/testing method. I always follow the same procedure. mash 10 to 25 bees with 1ml of water per bee. The challenge is you sometimes get a bee that skews the result due to extremely high infection rates. That's why Randy Os approach of brushing 10 bees one at time makes sense to me.
my goal is to identify hives that will need special attention in spring. That’s why I added the mortality number... as most of dying bees died for a reason... remember my winters are on average -10 to -20C... with typically a a week or 2 of -35 to -45C. Intense cold has an interesting effect on mortality rates. A really sick hive will get mounds of dead bees after it warms up back to average. Healthy hives don’t get this. Also my wrapping is not coming off so I have to develop a non intrusive process that works under my local conditions. Most of Nosema research is done under lab conditions and non in sub-Arctic conditions. I usually have N Ceranae but my spores look rounder this winter. I sent a sample to the lab to confirm type... most research doesn’t associate N Ceranae with this type of increased mortality during winter.🙂 my counts where zero in August for Nosema from bees off combs. The older forager bees will have the higher counts. So for me if those are clean then I am happy
Cleaning out Potentially Infected Equipment
Picture Below: Used vinegar on the poly boxes, plumber's torch on the wood frames, a peroxide solution on the wax frames and 48hrs of sunlight per side to disinfect my infected equipment (3 dead hives due to Nosema). The equipment was then re-used in 2018 in 4 new colonies (3 out of 4 show no signs of Nosema).
I am currently trialing Nozevit+ as a means of treating and helping my bees deal with Nosema. The treatment consists of mixing the "Oak Bark Extract" with 1:1 sugar syrup and feeding it to the bees once in spring and another time in fall.
I have also learnt to identify and deal with my honeydew honey.