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stock. It also suggests that old combs may harbor spores of the disease that persist to trigger the disease season after season. Research suggests that old combs should be replaced periodically to improve brood production.


Nosema is caused by the microsporidian Nosema apis (and the newly identified Nosema cerana), a small, unicellular organism that is unique to honey bees; it is the most widespread of the adult honey bee diseases. Nosema infects the epithelial cells of the honey bee ventriculus thereby causing dysentery. Queens, drones and workers are all susceptible to Nosema. The spore from the parasite must be ingested by the bee in order for infection to occur. The spore germinates in the midgut, penetrating the cell lining as it multiplies, reducing the life span of the honey bee. Nosema spores are spread to other colony members through fecal matter. Colonies in northern climates are more seriously affected than colonies in the south because of the increased amount of time bees are confined in the hive. Nosema, if left untreated, can cause queen supersedure, winter kills, reduced honey yields and dwindling populations. It is more common during times of confinement like winter and spring.

Symptoms of Nosema are vague and difficult to field diagnose. If you believe your colonies are infected with Nosema, send a sample of your bees in alcohol to your local county agent for verification.

The symptoms include: slow spring build-up (best indicator), disjointed wings, distended bloated abdomen, a lot of yellow streaks on the outside of colony and crawling bees outside of the hive. These symptoms may also be associated with tracheal mites.

Do not overlook this disease just because it is not common in the south. Prevention is the best way to keep your bees free of disease. Some good beekeeping practices are to avoid placing hives in low spots and to provide ample ventilation. Treat with antibiotic Fumidil-B® (fumagillin) according to the manufacturer's instructions.


Viruses are pieces of genetic material that parasitize a host cell, making the cell produce more viruses. No vaccines or medications are available for any of the honey bee viruses. Therefore, good sanitation practices are the key to prevention. Comb replacement and requeening are the best practical responses to a virus infection.

Beekeepers rarely consider sacbrood a serious threat; however recent estimates suggest that one larva killed by the sacbrood virus contains enough virus to kill over one million larvae.

More research needs to be conducted on the sacbrood virus since it is unknown how the virus is actually transmitted to the larvae in nature, why severe outbreaks occur only during the build-up season, or how the virus persists from year to year.  

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