Detection & Control of Brood Diseases

Healthy brood

• Pearly white larvae and convex (puffy) cappings on sealed brood 

Bacterial diseases

• Foulbrood; smelly
• American Foulbrood Disease (AFB): light to dark brown, dead larvae in a cell with a perforated capping. Consistency of dead larva is gooey or “ropy”. Atypical symptoms may be related to antibiotic treatments that work partially. 
• European Foulbrood Disease (EFB): yellowish, twisted dead larva in an uncapped brood cell.

Fungal diseases

• Chalkbrood and stonebrood diseases; dead larvae dry and hard; shape and size similar to a shelled, sunflower seed; not usually serious but individual colonies or even whole apiaries appear to be damaged by the chalkbrood disease occasionally.
• No treatment available. 

Viral diseases

• Sacbrood; larval skin is intact, but insides breakdown to watery consistency; seldom serious although individual colonies may suffer damage.
• No treatment available. 

Parasitic Mite Syndrome

• Looks like a combination of the above symptoms, sometimes difficult to distinguish from above diseases but the foul odor is missing. Seems to be related to mite infestations and is possibly caused by viruses.
• Treat for mites and the condition seems to clear up when mite populations are reduced.

Controlling Foulbrood Diseases (AFB & EFB) 

If AFB is detected the disease must be cleaned up in a timely manner so that the disease does not spread to neighboring colonies in the same apiary or nearby apiaries (within 2 miles).

Terramycin

Antibiotic available in different concentrations to be mixed with powdered sugar, salt, extender patty, in sugar syrup for EFB, Tetra B mix or other commercial formulation. Terramycin is to be used only as a preventative treatment.

Tylosin or “Tylan”

Alternative antibiotic to Terramycin. More research is necessary before a strong recommendation can be made.  Tylan could become important as AFB strains develop resistance to TM.  Tylosin is to be used as a preventative treatment only.

Fire

Destruction of equipment (woodenware, frames, combs…) by fire is still the only way to be confident the infection has been eliminated.

Disinfecting equipment

In some cases, woodenware (not combs) may be salvaged by scorching, lye water (one can of lye in 15 gallons of water and boil for 20 minutes), ETO fumigation, formaldehyde, hot paraffin dip or irradiation. 

Terramycin-Tolerant American Foulbrood Bacteria

• Must be treated as a new disease for which we have no drug cure.
• Therefore, destruction of all diseased material is mandatory.
• Samples of AFB may be sent to the Beltsville Bee Research Laboratory for testing for tolerance to Terramycin.
• Usually discovered because AFB persists after several treatments of Terramycin.
• Antibiotic extender patties may not work at all with this disease because the colonies may be getting under-dosed.
• Some colonies do not consume the whole patty or eat the patty so slowly that they do not get the full dosage of antibiotic. 

American Foulbrood Disease (AFB)

Cause

Paenibacillus larvae: a microscopic, rod-shaped, spore-forming bacterium

Effect

American foulbrood is the most widespread and destructive of the brood diseases.  

At first, the strength of an infected colony is not noticeably affected and only a few dead larvae or pupae may be present. The disease may not develop to the critical stage where it seriously weakens the colony until the following year, or it may advance rapidly and seriously weaken or kill the colony the first season. 

AFB spores infect very young larvae by entering the gut, germinating, then multiplying and growing while digesting the bee larvae for nourishment.  The honeybee larvae is killed in the process, but not before the bacteria have produced around 100 million spores.  These spores are then readily spread from the original brood cell throughout the colony by the bees and by basic beekeeping practices.  From the colony, the disease may then spread throughout the apiary, and further.  

Symptoms 

Death of an infected larva takes place after the cell has been sealed and the cocoon has been spun. First, the capping of the diseased cell becomes moist and darkens in color. Then, as the larva shrinks, the capping is drawn down in the mouth of the cell so the convex capping becomes concave. Worker bees may puncture this sunken capping and it may change from a normal pearly white color to a creamy brown, then gradually darkens. These larval remains can be drawn out into a brown thread or a rope. As the larva dries up, it becomes dark brown. The final state is a very dark brown, rather rough scale that lies uniformly on the lower side of the cell and extends from just below the mouth of the cell down to the base. These scales stick very tightly to the cell and can be removed only with great difficulty. 

The overall appearance of a brood comb infected with American foulbrood is spotty because of the intermixed diseased and healthy cells and also because the remains vary from the ropy moist larvae in cells with dark sunken or perforated cappings to the dry scales lying in open cells whose cappings have been chewed away completely by the bees. 

Transmission 

The bacterial spores are fed to young larvae by the nurse bees. They then germinate in the gut of the larva and multiply rapidly, causing the larva to die soon after it has been sealed in its cell. By the time of death of the larva the new spores have formed. When the house bees clean out the cell containing the dead larva these spores are distributed throughout the hive and more and more larvae become infected. 

The honey in an infected colony becomes contaminated with spores and can be a source of infection for any bee that gains access to it. For example, as a colony becomes weak, it cannot defend itself from attacks by robber bees from strong nearby colonies; these robbers take back the contaminated honey to their own colony and start again the cycle of infection and robbing.  

The beekeeper may inadvertently spread the disease by exposing contaminated honey to other bees or by the interchange of infected equipment (woodenware, comb) between colonies.  

Drifting bees or swarms issuing from an infected colony may spread the disease. 

Treatment for AFB Infected Colonies

Disease control is primarily the responsibility of each beekeeper, who must learn the symptoms of the diseases and inspect the colonies carefully for the presence of American foulbrood. Inspect your colonies several times per year. Bee diseases are spread more often within beekeeping operations than between them, and lack of inspection is a major cause of such spread. Get to know your bees. Familiarity with healthy colonies is essential to the detection of problems when they arise. Also, take advantage of your State Apiary Inspectors. Our program exists to advance beekeeping. In Iowa, apiary inspection is provided with no fee for the service. Contact the State Apiarist for details. 

The ONLY treatment for AFB infected colonies is destruction of all Bees and Comb. Woodenware may be disinfected, but the beekeeper should evaluate the costs / benefits / risks involved with disinfection rather than destruction of woodenware. For smaller amounts of equipment destruction by fire may be the most practical method of disease eradication. For any amount of contaminated equipment, the safest method of AFB eradication is destruction of all infected bees and all infected equipment. Questions concerning the destruction of contaminated equipment should be directed to the State Apiarist.

The best methods of control are Apiary Inspection and treatment for prevention prior to the existence of AFB symptoms. Countless attempts of saving and treating diseased colonies have been tried and found to be ineffective. Methods of “saving” / “salvaging” infected woodenware sometimes require more expense and labor than the value of the diseased colonies. When not done properly, the treatments often spread disease.

Chemical treatment of existing AFB with Terramycin (TM) will only control the symptoms of the disease. TM only serves to prevent bacterial growth during the duration of time when TM is present in low concentrations in the food fed by the workers to larvae. 

Terramycin treatment does NOT destroy the bacterial spores. The spores remain viable in the hive for decades.   

The colony may recover from the symptoms of the disease, but the bees will NOT be free of the AFB bacteria.

AFB from TM treated colonies may still be spread to other hives.

Disinfecting Woodenware  For AFB Eradication

Viable American Foulbrood (AFB) spores remain in comb and woodenware for decades. Destruction of entire frames, comb, and boxes by fire is the safest method of killing the spores and preventing further infection of colonies. 

Comb and bees must not be salvaged from diseased colonies. 

For those wishing to save their contaminated woodenware from destruction, there are a few methods of killing the AFB spores from the woodenware surfaces.

The inside surfaces of the woodenware can be scorched by fire. This can be done with a propane torch, completely blackening the surface so that all wax and propolis is removed. This can also be accomplished by “painting” the surfaces of the boxes with kerosene, stacking the boxes, and setting them alight. When surfaces are significantly charred, the flame should be smothered by covering the top of the stack of boxes. 

Boiling woodenware in lye water for 15 minutes (1 can of lye per 5 gallons of water) can disinfect boxes and scraped frames. This can be accomplished by bringing a barrel of lye water to a boil and submerging the woodenware for the full duration of time. F

inally, beekeepers in some locations may have access to ethylene oxide fumigation or irradiation facilities.