Bee Brothers Apiary
Silver Bay, New York
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Bee Diseases & Pests: American Foulbrood
American Foulbrood (AFB) is an infectious brood disease
caused by the spore forming bacteria Paenibacillus larvae.
It is a highly contagious and destructive disease. The
spores can remain viable for long periods of time, under
adverse environmental conditions, making is difficult to
control its spread. However, AFB is destructive to the
larvae only and it does not affect adult bees or older larvae.
A colony that is infected with AFB will have a scattered and irregular pattern of capped and uncapped cells. The infected cells are discolored, sunken, and can have punctured or perforated cappings. As the cells die off, they turn from a healthy pearly white to a dark brown color. Death usually occurs in the final days of the larval stage or the first few days of the pupal stage. After death, additional bacteria spores form, therefore, increasing the potential for its spread.
For up to 3 weeks after death, these cells have a glue-like consistency. When a cell is mixed with a toothpick, the contents can be drawn out an inch or more when the toothpick is withdrawn. If death occurs during the pupal stage, the pupae will go through the same change in color and consistency as the larvae. In addition, the pupal tongue will stick up from the remains toward the top wall of the cell. This, along with a foul order, is one of the most characteristic symptoms of the American Foulbrood disease.
The spread of AFB can be caused in a number of ways. The following are the most common means of a hive becoming infected:
- Nurse bees feed infected honey to the young.
- Healthy bees robbing an infected hive.
- The use of second-hand equipment which contain spores.
- Beekeepers interchange combs of brood and honey between infected and healthy hives.
There are also many precautions that, as a beekeeper, you can take to prevent the onset and infection of AFB. Below is a short list of precautions you can take to reduce the likelihood of an AFB outbreak.
- Never allow bees access to honey, cappings, and hive scrapings.
- Never interchange comb between a healthy and a infected hive.
- Do not use second-hand material.
- Never allow a hive to become neglected. If proper management and maintenance of the hive is no longer possible, sell or give it away.
- Always inspect all brood combs each spring for the presence of AFB. Early detection increases the chance of saving the hive from destruction.
- Always sterilize the hive tool and wash the smoker, hands and/or gloves after working on a hive that you may suspect to be infected. We recommend you follow this practice when moving from hive to hive or apiary to apiary.
- Never remove a hive with AFB from an apiary until the infection has been eradicated.
- Testing samples for the presence of AFB. (Diagnostics kit or matchstick test).
Along with above mentioned preventative measures you can take for AFB, many beekeepers use terramycin. It is an approved antibiotic for preventative treatment against American Foulbrood. This antibiotic does not kill the Paenibacillus spores, but prevents or delays their growth when present in low concentrations in the food fed by workers to susceptible larvae. While this treatment allows individual larvae to survive, it does nothing about the virulent spores that are already in the contaminated equipment. Thus, the disease usually reappears once the drug feeding stops.
Preventative terramycin treatments are normally made in early spring well in advance of the major nectar flow, and again in the fall after the honey crop has been removed. There is the pre-mixed form, which you would scatter a few tablespoons over the top bars. There is a pure form terramycin for those Beekeepers interested in making their own patty or powder. Finally, a patty form Terramycin that gives the bees a continuous supply for a few weeks. The patty form is applied by squashing the patty down on the top bars of the brood chamber that contains the majority of your bees. These are typically used for the fall treatment.
Although AFB cannot be transmitted to humans and has no effect on honey for human consumption, due to the highly contagious and devastating action of the disease, every Beekeeper should know the symptoms and be able to recognize AFB in its early stages. If you suspect that your hive is contaminated, and need help in the diagnosis, contact your local apiary inspector.