What Is Nosema? Research-Backed Advice For Beekeepers
Nosemosis, commonly called Nosema disease, is triggered by two fungi: Nosema apis and Nosema ceranae. It affects the bee’s digestive system and can cause severe colony losses in spring and fall.
N. apis originally affected European honey bees, while N. ceranae targeted Asian honey bees. However, N. ceranae has recently begun harming European bees and is more destructive than N. apis.
The infection causes young adult bees to become early foragers, skipping the nursing phase. Their lifespan shortens, and if queens get infected, they lay fewer eggs. Nosemosis harms the bee colony’s health and size, potentially leading to its collapse.
Important: Low numbers of Nosema-infected bees is common in hives. A healthy, thriving colony will usually fight off the disease.
Symptoms of Nosema
Nosema-infected bees typically exhibit no symptoms; any signs can be attributed to other threats. Beekeepers should get a sample of bees laboratory tested for a reliable diagnosis.
A heavily impacted colony may experience adult bee deaths at a rapid rate. Expect minimal dead bees at the hive’s entrance; dying bees will crawl away from the hive.
The colony is impacted my Nosema in several ways, including:
- Dysentery in adult bees.
- Life expectancy of infected bees is reduced by up to 50%.
- Nurse bees are unable to produce royal jelly.
- Young bees prematurely start foraging or guarding.
- Queens stop laying eggs and soon die.
Nosema ceranae vs. Nosema apis – what’s the difference?
Nosema ceranae and Nosema apis are both microsporidian parasites that infect honeybees. Nosema ceranae was initially identified in Asian honeybees but now impacts the Western bee in most parts of the world.
Although knowledge is limited on N. ceranae, most of its characteristics are shared with N. apis. Nosema ceranae has a more severe effect on a bee’s digestive system than Nosema apis.
Nosema Apis was identified over a century ago, while Nosema ceranae wasn’t found until 1994.
Comparison summary table:
| Nosema apis | Nosema ceranae | |
| Family | Nosematidae | Nosematidae |
| Genus | Nosema | Nosema |
| First discovered | 1909 | 1994 |
| Detected | Mild weather | All year round |
| Number of gut cells affected | Less | More |
| Bee mortality rate | Lower | Higher |
| Dysentery symptoms | More pronounced | Less pronounced |
Life cycle and spread
Nosema is spread on honey and pollen. When bees ingest Nosema apis spores, they germinate in the stomach within 30 minutes. The organism then invades the stomach cells, proliferating rapidly by consuming cell contents.
In 6-10 days, vast spores form in these cells. The parasite can also infect neighboring cells, spreading the disease.
During digestion, bees naturally shed stomach cells, releasing enzymes. Infected cells, however, release nosema spores instead. These spores can infect other stomach cells or exit with the bee’s feces.
Young bees get infected when they consume spores while cleaning tainted combs. In summer, many bee colonies have a few infected bees, but the impact is often minimal.
In fall and winter, spores within the hive may trigger a Nosema outbreak. Bees trapped inside by bad weather may defecate inside the hive, contaminating it with spores.
The infection may result in severe casualties until the weather warms, allowing bees to leave the hive.
Related reading:
- A beekeeper’s guide to black queen cell virus.
- A beginner’s guide to sacbrood disease.
- What is Kakugo virus?
- How does stonebrood impact the colony?
- What is IAPV? Guide to Israeli acute paralysis virus.
Fast facts
- Rapidly reducing colony numbers is also referred to as “spring dwindle.”
- Common symptoms of Nosemosis, like dysentery and sick crawling bees, are also associated with many other hive problems.
- Infected adult bees rarely transmit the disease directly to their brood.
- When N. ceranae spores are chilled or frozen, they lose viability.
Prevention
Beekeepers can help prevent Nosemosis in their apiaries by reducing nutritional stress and pesticide exposure. Research has found these two factors play a huge role in the disease’s impact on bees. Source.
Other preventative measures include:
- Locating hives in a sunny location away from damp gullies and areas that are wind prone.
- Keeping prolific queens that lay a lot of eggs.
- Ensuring there is a large number of young bees as winter approaches.
- Making sure bees have adequate supplies of honey for winter.
- Avoiding hive inspections or other disruptions to the hive unless essential.
- Reducing hive space during winter helps keep the colony warm and reduces the area to guard.
- Avoiding crushing bees during hive management, as undertaker bees will spread the spores if the deceased bees are infected.
- Removing the oldest, darkest comb each spring and replace it with fresh, new foundations.
Recommended reading: A practical guide to chalkbrood.
Commonly asked questions
How is Nosemosis diagnosed?
Nosema infection is diagnosed using microscopy and nucleic acid technologies; only electron microscopy and PCR reliably differentiate between Nosema Apis and Nosema Ceranae spores.
What is the impact of Nosema on honey bee colonies?
Nosema typically reduces the lifespan of worker bees, decreases honey production, and weakens the overall health of a colony. In severe cases, it contributes to colony collapse.
Is honey from Nosema-infected colonies safe for humans?
The honey produced in hives with Nosema is safe for consumption.
Can Nosema disease affect humans?
Nosema is not transmissible to humans.
How to treat Nosemosis
Treatment of Nosema varies by country, and beekeepers should consult local authorities before implementing eradication strategies.
Fumagilin-B is a chemical treatment that is effective against Nosema disease. It is commonly used in the United States; however, the product is prohibited in some countries like Australia. For the most part, this chemical is not authorized in Europe. Source.
Research articles about Fumagillin-B
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Sources
- https://www.sciencedirect.com/science/article/abs/pii/B9780123849847000026
- http://entomology.ucdavis.edu/files/147621.pdf
- http://scientificbeekeeping.com/nosema-ceranae-not-your-fathers-nosema/
- https://en.wikipedia.org/wiki/Nosema_apis
- https://onlinelibrary.wiley.com/doi/10.1111/j.1744-7348.1955.tb02488.x
Image attribution: “Courtesy The Animal and Plant Health Agency (APHA), Crown Copyright”
