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American Foul Brood

Overview

American foulbrood (AFB) is a bacterial infection caused by the bacterium Paenibacillus larvae. The bacterium have two states:

1. the vegetative state (when it actively causes infection and reproduces) and
2. the spore state (when it does not cause infection).

The vegetative bacterium reproduces by creating many spores, which can be found in honey and bee bread, as well as on wax and woodenware.

How it is Transmitted

Nurse bees pick up the spores from food or from feeding an infected larva. Those nurse bees then feed the spores to young larvæ when feeding them.

All castes of bees a susceptible to being infected, but only within the first three days after they hatch from the egg.

What's the Big Deal?

In may states, the incidence may be relatively low, but elsewhere the problem persists. And the real problem is that the bacteria remain alive in the spore state for over 40 years. The long-lived spore is resistant to changes in the weather, hot and cold temperatures, bactericides, and antibiotics. Colonies that are positively diagnosed need to be managed carefully and immediately to reduce the chances of the infection spreading.

Symptoms

The early and late stages of a colony infection have different symptoms. In the early stages, you can expect to observe the following:

• Spotty brood pattern with sunken/concave or perforated cappings.
• Caramel or coffee-coloured prepupæ.
• Prepupæ laying flat on the lower cell wall with a mucous consistency.
• Prepupæ stringing out into nearly inch-long "ropes" (2 cm) when pulled with a toothpick or small twig. (Note that prepupæ in the very early stages of infection may not rope out.)
• If death occurs in the pupal stage, some pupæ may have their tongues sticking out.
• Distinctive foul odour in some cases (though not all cases). The odour smells similar to old gym socks. It is worth noting that colonies can give off a foul odour in other circumstances, such as during infections of European foulbrood, during brood decay after prolonged colony death by any cause, and during the ripening of goldenrod honey.

In the late stages, usually after a colony has died or when the colony is nearing death, you can expect to observe the following:

• Dead prepupæ become a thin, dark scale along the lower cell wall. In this stage, they are no longer "ropy." This scale does not pick out if you scrape it with a toothpick or small twig.
• Distinctive foul odour in some cases (though not all cases).
• Few adult bees present (toward the ultimate demise of the colony).

Inspecting for an AFB Infection

Comprehensive inspections for AFB should occur thrice yearly. At those inspections, do a comprehensive inspection for AFB (spring, post honey harvest, and before wintering). This requires you to go through every brood frame in every hive, looking for the symptoms described on the previous page. To make sure you don't miss any cells, shake the bees off the frames as you check them.

Notice whether the brood pattern is solid or spotty, then carefully examine the frame to look for cappings that are concave or perforated. Anytime you see a cell like this, use your hive tool or a small twig or toothpick to open up the cell. If you see a larva or pupa that is the distinct caramel colour, it's time to do a test. Even if only one cell is affected, test it. It's best if you catch the infection in an early stage.

Testing for an AFB Infection

1. Vita Bee Health sell an AFB test kit which is a good one to use for field-testing.
2. The USDA's Beltsville Bee Lab also allows you to send them a sample to the bee lab in Beltsville, Maryland. The Beltsville Bee Lab processes samples from US sites free of charge. They test for the presence of European foulbrood, as well as antibiotic resistance. It is important to determine whether any confirmed infections are resistant to traditional antibiotics. Information on how to submit a sample to the Beltsville Bee Lab can be found at their web site, (How to Submit Samples).

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More Information

Published Articles

• American Foulbrood of Honey Bees (Paenibacillus larvae), by the USDA
• Identifying and Mitigating Foulbrood in Honey Bee Colonies and reducing the use of Antibiotics: Information for Beekeepers and Veterinarians from the Honey Bee Health Coalition

Web Sites

• American Foulbrood at The Ohio State University
• Ohio Revised Code Section 909.11 | Additional control and eradication measures