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American Foulbrood Disease

American Foulbrood Disease was seen in a recent outbreak in the Dartmouth Cole Harbor area 2021 and so this blog post on the disease seems timely.

Caused by the spore forming bacterium Paenibacillus larvae, it attacks weak and strong hives alike, without preference and is fatal for the affected colony. After attacking the larvae, infected brood dies at the pupae life stage. Once infected, there is no treatment regime that will kill off the AFB spores, therefore biosecurity of the affected hive becomes paramount so that spread does not occur. Provincial Bee Acts are very clear when it comes to follow-on actions once detected. More to come on that requirement.

But first we will look at detection. It smells bad, almost like rotting fish which speaks to the name "Foul Brood" and is probably the reason the hive is not growing well!

AFB infected hives usually have a brood pattern shown in the picture as irregular or "shotgun " pattern. Brood caps are normally sunken, dark and concave, and maybe a bit greasy looking. Caps often have irregular perforations and or caps completely removed, exposing rotting larvae and pupae.

A frame infected by American Foulbrood Disease
American Foulbood Infected Frame

Enter the rope test. Brood infected by AFB will change in color from off white to darker coffee brown, a part of the process that happens in capped cells as the larvae die and rot, Once dead, the contents of the cell become very sticky. The rope test is accomplished by slowly inserting a twig into the affected cell and slowly pulling it out. If there is what looks like brown mucus stringing out from the twig to cell, the beekeeper should consider that AFB is present. Left untended, the dead larvae dry into a black scale that is near impossible to dislodge without damaging the cell.

Confirmation of your Diagnosis:

Use a commercially available foulbrood testing kit that will provide a definitive confirmation. A google search reveals this kit as a popular choice and they are normally available at bee supply outlets.

What do you do now its confirmed?

The first thing you must do in Nova Scotia in accordance with the NS Bee Act is to report the disease to the provincial Apiarist.

American Foulbrood Field Test Kit
AFB Field Test With Positive Indications

Current practice is to euthanize the colony and destroy all the woodenware by burning.

Remembering that there is no recognized cure for the disease, it remains very important to treat with "prevention in mind" any other hives in the apiary or close by. Colonies in high risk areas are normally treated with Oxitet-25 (Oxytetracycline) as a prophylactic measure.

You will need a veterinarian prescription to buy Oxitet - 25 in Nova Scotia.

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