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Vairimorpha

Vairimorpha apis (previously known as Nosema apis) was first discovered in the early 1900s and for a long time, it was the only Vairimorpha species infecting Apis mellifera.

• In 1996, Vairimorpha ceranæ (previously known as Nosema ceranæ) was discovered to be infecting the Asian honey bee, Apis cerana. It produces more spores in the bees' guts than Vairimorpha apis.
• Ten years later in Spain, the Vairimorpha ceranæ infection was observed in Apis mellifera. (Older samples confirmed that it crossed over to Apis mellifera in the late 1970s.)

In early 2020, a genetic analysis revealed that the fungal species infecting honeybees which are commonly called Nosema are actually members of the genus Vairimorpha. Thusly, they have been renamed:

Overview

Vairimorpha is a fungal disease which affects the digestive system of adult bees.

• It is very common throughout the world.
• It is not a major cause of honey bee colony losses in the USA; other nutritional causes are more likely.

Vairimorpha produces spores, and once the spores are consumed, they travel to the bee’s intestine where they become active and infectious. The active fungus feeds on the bee to acquire all the nutrients and energy it needs. It reproduces by producing spores, which then exit the bee's body in defecation. Infected bees can contain as many as 30 to 50 million spores in their midguts. The presence of spores does not cause symptoms in bees, but the active fungus can.

• It can infect all castes: queens, drones, and workers
• It usually develops in Spring or Fall
• Pesticide exposure increases probability of infection (esp. imidacloprid)
• It can only be diagnosed through microscopic examination or molecular analysis

Vairimorpha ceranæ can infect a number of bee species:

Vairimorpha ceranae has increased in prevalence worldwide, and the documented cases in North American show that it outcompetes Vairimorpha apis over 99% of the time.

Symptoms are below.

Integrated Pest Management

Control Methods

Cultural

1. Ensure your apiary has good drainage & sun in Winter
2. Ensure you use clean hive tools
3. Reduce hive moisture
4. Increase hive ventilation
5. Reduce pesticide exposure
6. Rotate brood frames out

Treatment Methods

Cultural

1. Discard frames with >10% infection

Genetic

1. Re-queen

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Additional pictures of this

More Information

Web Sites

• Vairimorpha apis (Wikipedia)
• Vairimorpha ceranæ (Wikipedia)