Nosema-By Joe Myers- Cornell Univ. Master Beekeeper 

Nosema-

Nosema is a fungal gut parasite that can be harmful to honey bee health, and if severe, can lead to the total collapse of a honey bee colony. Here we provide a description of the types of Nosema, associated characteristics, and actions that can be taken to mitigate.

The two types of known Nosema are Nosema apis & Nosema ceranae, which are also known by the newly recognized name of “Vairimorpha apis and Vairimorpha ceranae”. For the purpose of using general recognized terms, we will refer to Nosema apis & Nosema ceranae in this presentation.

Specifically:

• Nosema disease is prevalent worldwide

• Nosema infection vulnerability may be increased when exposed to pesticides (such as

neonicotinoids).

• The Nosema parasite can kill colonies that are unable to clear the infection

• Spores enter the body via - ingesting fecal matter; nestmate grooming; trophallaxis

(mouth to mouth transfer of liquids via proboscis); cleaning contaminated cells; etc

• Colony to colony transfer is a means of transmission

• Can be transmitted by drone sperm

Nosema apis:

• Specific to honey bees (long established parasite of European honey bees)

• In North America Nosema apis is rare

• Dysentery is associated with Nosema apis

• It is believed that Nosema apis inhibits digestion, and as such bees become dysentery, and as such defecate inside and outside of the hive (instead of in flight)

Nosema ceranae:

• Dominant Nosema species (originally infected Asian honey bees Apis cerana and later

jumped to Apis mellifera)

• Can infect honey bees and other bees and insects (such as bumble bees)

• Dysentery is normally not a symptom seen in Nosema ceranae

Symptoms:

• Colony stress

• Parasite infection reduces fat bodies

• Parasite uses up energy from host bee leading to starvation (bee has decreased energy to

perform tasks)

• Decreased adult population

• It has been noted that infected bees will die far from the hive; possibly due to lack of

energy and being disoriented.

• The only way to diagnose Nosema disease is through microscopic examination (such as

with a microscope or by sending a sample out to the Beltsville, MD Bee Research Lab)

Dysentery:

• Dysentery may or may not be associated with Nosema (there may be other contributors);

when in doubt, have tested

• Dysentery can be caused by nutrition issues:

- Consumption of fermented honey

- Unrepented honey/sugar syrup (i.e. when confined in their hive for long periods)

Dysentery “streaks” (inside of box)

Unripened honey

How to minimize risk:

1. Monitor moisture in the hive (keep well ventilated)

2. During long periods of confinement (winter) minimize uncapped honey/sugar syrup

3. Consider a microbial supplement in your bee’s diet (such as DFM *) to promote good gut

health

4. Keeping colonies healthy can reduce Nosema spore count

5. Disinfect equipment to reduce contamination risk

6. Infected hives should have frames and hive equipment treated (i.e. with acetic acid; treat

with heat 140f for .15 minutes; or other recommended methods)

7. If Nosema is suspected, consider contacting the Beltsville, MD Bee Research Lab

* SuperDFM Honeybee Microbial Supplement- can support bee gut health and microbiome

Beltsville, MD Dept of Agriculture Bee Research Lab:

https://www.ars.usda.gov/northeast-area/beltsville-md-barc/beltsville-agricultural-research-

center/bee-research-laboratory/

How to submit samples:

https://www.ars.usda.gov/northeast-area/beltsville-md-barc/beltsville-agricultural-research-

center/bee-research-laboratory/docs/how-to-submit-samples/

• Lab Test Diagnosis

General Nosema Spore Thresholds:

<1 mill → low

1-5 mill → moderate concern

5-10 → high concern

>10 mill → severe

For specific guidance on how to best manage suspected Nosema, we recommend

contacting the Maryland Department of Agriculture State Apiarist Inspector Cybel

Preston @ cybil.preston@maryland.gov