By Shelli Quattlebaum
(Apiary Inspector of America and Colorado Department of Ag, Apiary Specialist. Contacted for the 2024 season)
In early October I confirmed AFB while surveying an apiary for the National Honey Bee Survey.
First upon smelling it, then visual. American foulbrood (AFB) is a bacterial disease that affects honey bee larvae and pupae, and is considered the most destructive and widespread honey bee brood disease.
I performed a mechanical test “rope test” and finally a VitaBee Health AFB test, confirming my findings.
Samples were sent to the Beltsville bee lab for testing by the USDA
A disc diffusion assay was conducted to determine the sensitivity of the P. larvae to antibiotics.
The inhibition zone for Tetracyline was 70mm and the inhibition zone for Tylosin was 78mm.
The USDA lab test shows that this P. larvae is not resistant to medication and is treatable.
This information was forwarded on to the beekeeper.
I put the beekeeper in contact with Dr. Amy Franklin our local BeeVet to give a Veterinary Feed Directive for appropriate treatment on the day of sampling.
In addition, I gave information from the CDA about RULES AND REGULATIONS PERTAINING TO THE ADMINISTRATION AND ENFORCEMENT OF THE BEE AND BEE PRODUCTS ACT.
A few key point from the Colorado Regulations:
Upon finding what appears to be diseased material in any apiary, if the owner is present and agrees with the findings of disease, abatement procedures shall be commenced immediately as directed by the Department.
Sterilization of any and all bees infected with or exposed to any equipment exposed to a contagious bee disease, by burning said bee equipment and burying under at least 12 inches of earth.
Application of a powder consisting of approximately 3.5 percent by weight terramycin and approximately 96.5 percent by weight of one or more non-toxic substances applied to tops of brood frames at rate of approximately one tablespoon every four days for a period not less than three consecutive weeks; or by application of such other medical treatment as may hereafter be determined by the Commissioner to be equally effective. Must retain VFD for prescription for Tetracycline or Tylosin.
If any contagious disease is found in any hive, the entire apiary shall be placed under quarantine and no colonies can be sold, destroyed or moved or transferred into or out of the apiary without the written permission of the Colorado Department of Agriculture. All such diseased hives found shall be medically treated, chemically sterilized or sterilized by burning.
The method used shall be one acceptable by the Commissioner.
AFB is not a reportable disease in Colorado.
How can you identify and test for American Foulbrood effectively…
A step by step action plan
Smell:
Opening your hive and being hit with the smell of wet gym socks.
A foul smell! Infected hives may also have a sulfurous smell due to the decomposing brood.
Visual inspection:
You see irregular and patchy brood patterns.
Cell capping's on infected brood may appear sunken, darker colored or greasy. This is due to the decomposing larvae inside.
Capping's may also be perforated by bees trying to remove the dead brood (the remains of which are infective).
Closer inspection of individual cells in the advanced stages of infection will show that:
Infected brood changes from a healthy pearly white to a dark brown (a ‘ropiness test’ can be carried out at this stage – see Detection tab).
The dead larval remains become a tough, but brittle scale that is difficult to remove from the cell.
If older larvae are infected the ‘tongue’ of the pupae may become stuck to the top of the cell wall.
Field Diagnosis:
A ropiness test can be used to diagnose AFB.
Poke a brown pupal mass with a toothpick, match, or other small object, then slowly pull it out.
Beekeepers should conduct the ropiness test on suspect cells before the scale stage of infection.
The test is as follows:
Identify a suitable cell showing AFB symptoms – discolored, greasy, perforated or sunken capping's.
Push a matchstick into the infected cell
Slowly withdraw the match
If the semi-fluid remains are drawn out in a 3–5 cm long dark-brown ropy thread it indicates the hive could be infected with AFB.
If the semi-fluid remains are drawn out but only form a short (usually less than 1.5cm long) light gray semi-liquid mass, then the disease is likely to be European foulbrood (EFB; Melisococcus plutonius).
However, EFB infections with Paenibacillus alvei (a secondary infection associated with EFB) may also cause some extra ropiness which makes EFB infected brood produce a longer thread and resemble AFB infected brood.
A key means of differentiation between EFB and AFB is that EFB usually kills brood prior to capping; while AFB infected brood usually die after capping.
Always remember that these are simple field guidelines, and the only accurate means to differentiate EFB from AFB is through laboratory diagnostics.
You can also do a Holst Milk Test
Holst milk test
Make a weak milk solution containing 1 tsp powdered milk and 100 ml water (a little less than ½ cup).
When the powder is dissolved, divide the mixture into two small glass containers.
Gather as much brown pupal mass material as possible using a toothpick, match stick, or leaf stem.
Add the pupal mass material to one of the containers with the milk solution.
Put both containers in a warm place for one hour (without adding anything to the second container).
A positive test will result from the liquid turning clear brown.
The control tube (without the pupal mass material) should show a whitish liquid (Image 7).
Image 7
Common Errors to Avoid
Avoid mixing the milk too concentrated – it may be difficult to witness a change, resulting in a false negative result. Avoid sampling pollen.
While there are no known pathogens besides P. larvae that have the effect of breaking down milk proteins, similarly functioning enzymes may be found in pollen, resulting in a false positive result.
This test will not work at room temperature.
The samples must be incubated around 37°C/99°F for AFB-positive samples to clear.
Backlight visualization
AFB scales glow under a black light.
Shine the light onto the frame. Scales will glow with a greenish-bluish color (Image 6B).
6B
Good colony management practices
Beekeepers should check brood combs at least twice a year (spring and autumn) for early signs of AFB. As a precautionary measure, brood combs should be replaced every 3-4 years as old brood combs can act as a reservoir of the bacterium.
A key aspect of good colony management also involves the beekeeper reducing or preventing the interchange of hive materials that can spread AFB amongst hives, or to different apiaries.
AFB spores are very difficult to kill and easily transferable between hives.
AFB can be accidentally spread on tools or via normal beekeeping practices, so look at implementing simple measures such as cleaning tools between hives and taking care when moving material between hives in order to reduce the spread of AFB and other pests.
If you notice that some hives are infected with AFB, always clean your beekeeping gear before inspecting a new apiary.
If AFB is detected in a colony, there are two options in dealing with the hive.
The first option is to kill the colony (including the frames) and irradiate all box parts which will destroy the AFB spores.
If irradiation is not possible, it is recommended that all hive components are buried in a deep pit and burnt.
If the burn and bury option is followed, always ensure that the hive entrance and any other openings are closed so that bees are not able to escape.
Once the hives have been burnt, bury the remains in the pit.
For more information about these control measures, see the Videos tab.
More Information Information:
You can purchase AFB and EFB tests online as well from VitaBee Health. https://carolinabeefarm.com/American-Foul-Brood-Kit
If you suspect AFB, and your stat has an Apiary program, call the apiary inspector.
They will come and sample your hive for AFB and send it out on your behalf to the USDA laboratory for conformation. There are some forms of AFB that are resistant to antibiotics.
The USDA lab will tell you if your strain is resistant or not, and then you cant treat accordingly.
The apiary inspector will help connect you to the web of people you need to talk to to amend your situation. In Colorado there is no Apiary Program and no one to call at the state level. Reach out to Dr. Amy Franklin, she can providing testing and write a prescription for atibiotics to treat. and of course you can always email me for direction. Stay well and be kind to one another Shelli
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