American foulbrood

AFB is caused by a spore-forming bacterium, Paenibacillus larvae var larvae.

AFB has been detected in all states and territories in Australia. The prevalence of the disease can vary from region to region over time.

The pathogen has both a reproductive stage and a resting stage (during which it forms spores). These spores can lay dormant for 50 years or more and are not killed by regular disinfectants or moderate heat (such as the flame of a smoker).

At first, diseased larvae or pre-pupae are slightly yellow. As decomposition advances, they become coffee-coloured and extend lengthwise in the cells.

After stirring with a match or similar probe, the contents of the cell may rope out and form a fine elastic thread up to 30mm long.

In the advanced stages, the brood pattern has a pepperbox appearance.

On drying out, the diseased larvae or pre-pupae become dark brown and form a scale along the lower cell wall. Good lighting is needed to see these scales, as they are similar in colour to dark brood combs.

Cappings, if present, will be either:

• perforated—often with off centre pinhole size perforations
• if the disease is well established, most of them will be sunken and appear water-soaked.

Where death has occurred during pupation, a partly developed tongue may protrude as a fine thread upwards and backwards from the scale. Under Queensland conditions, this symptom is rare.

AFB may be confused with:

• sacbrood
• European foulbrood (EFB)
• mystery brood disorder.

AFB can spread through:

• robbing
• feeding unsterilised honey or pollen
• using contaminated beekeeping equipment
• drift.

Prevention

• Don't feed your bees honey or pollen unless it has been sterilised using gamma radiation.
• Don't use second hand or borrowed equipment on your hives without sterilising it first.
• Maintain strong bee colonies to prevent robber bees which may bring the disease with them.

Avoid robbing

Robbing behaviour may start when:

• bees gain access to sticky combs, burr comb, or dead-out hives
• day length shortens
• there is cloudy weather
• there is a lack of nectar.

As it progresses, bees fill the air and become aggressive. Weak hives will be killed-out first and many hives can be lost.

To avoid robbing behaviour:

• feed bees sugar syrup during periods of low nectar availability (dearth). This may prevent starvation and robbing
• keep any waste material, extracted combs and dead hives in bee-proof areas or wrappings.

Do not feed unsterilised honey or pollen

Never feed cappings honey or extracted honey to bees. This honey is a mixture from many hives and has a high risk of spreading disease.

Irradiate pollen before use to kill disease organisms.

If feeding honey, first test the honey for disease organisms or feed bees sugar syrup.

Do not use contaminated beekeeping equipment

Do not use any equipment unless it has been decontaminated after handling infested hives. Refer to the Control section below.

Drift

Drift occurs when bees from one hive enter another.

Bees infected with spores of AFB can drift:

• from hive to hive within an apiary
• during open entrance loading and migration on trucks or trailers.

AFB affects unsealed and sealed brood. Young larvae, less than 24 hours old, are most susceptible to the infection.

Check your hive regularly for AFB, preferably at 6 to 12 weekly intervals.

You need:

• a hive tool
• a smoker
• protective clothing
• a matchstick
• a sealed container for waste
• a small clean plastic jar for sending away disease samples.

Method:

• Remove the hive lid, any supers (boxes of frames on the top with only honey) and the queen excluder and place them to the side of the hive.
• Remove brood frames (frames in the bottom box) one at a time—use the hive tool to loosen them if necessary.
• If you can identify your queen, check each frame for the queen, and gently replace the frame containing the queen, before checking the remaining frames.
• If you can't identify your queen, you can still inspect the brood—ensure you shake the bees on the frame back into the same box they came from.
• Shake bees off the frame so you can clearly see the brood—ensure you shake the bees on the frame back into the same box they came from.
• Closely examine the brood for any cells which look abnormal.
• Poke a matchstick into one of the dark and shrunken brood cells and swirl it around the cell.
• Pull the matchstick out. If a thick ropey brown decomposed gooey material comes away with the matchstick it is very likely you have AFB or European foulbrood (EFB) disease.

It is difficult to identify the difference between AFB and EFB. You can send samples to the Biosecurity Sciences Laboratory to determine whether your hives are infected with American foulbrood.

It is essential that you prevent the spread of the disease to minimise its impacts on:

• your and other beekeepers' hives
• the honey bee industry
• plant industries that rely on pollination and the environment.

Kill bees in infected hives

Wait until evening when all the bees have returned to the hive from foraging.

Either:

• Shake bees off any honey frames into the brood box and place the brood box with bees in the freezer for a week. Ensure there is no honey present as the bees will stay alive. After a week, remove the brood box from the freezer, check to see that all the bees are dead. If there are still some live bees return the brood box to the freezer for several more days.
• Use sufficient dishwashing liquid to make water soapy. Use a spray bottle or tank and hose, and spray bees with enough soapy water to wet all bees at once. Alternatively, use a large tub to submerge the bees or hive. Refer to Australian Pesticides and Veterinary Medicines Authority permit PER90262 (PDF, 100KB).
• Use unleaded petrol to euthanise bees. Refer to Australian Pesticides and Veterinary Medicines Authority permit PER92753 (PDF, 112KB) for detailed instructions.
• Use specific permethrin formulations to euthanise bees. Refer to Australian Pesticides and Veterinary Medicines Authority permit PER88802 (PDF, 80KB) for detailed instructions.

Secure any potentially contaminated items

Until you can decontaminate or destroy contaminated items, secure them in a sealed container which bees cannot access:

• anything that you take out of the hive
• any tools or protective clothing that you have used while working an infected hive.

Decontaminate hives, frames, bee products, tools and clothing

Decontaminate all potentially contaminated items:

• hives
• hive tools and other tools such as knives that you may have used on the contaminated hive
• protective clothing worn while working with infected hives
• other beekeeping tools such as smokers
• other items from hives such as beetle traps
• all workers should wash their hands, shoes and clothing.

There are 4 options for decontamination.

Burn and then bury all potentially contaminated material:

• Ensure that you have a fire permit if required and that there isn't a fire ban in place.
• Burn all your frames, bee products, hives and protective clothing in a hot fire.
• Scrape or use hot water to remove the wax from any tools used on hives and then use a blowtorch to scorch the equipment.
• Bury the remnants of all burned material (excluding scorched tools) at a depth of at least 30cm.

Sterilise hives and equipment using gamma radiation:

1. Remove any wax or honey from the hive to prevent leaking during treatment. Burn and bury any removed material.
2. Wrap hives and any equipment in thick plastic to ensure that bees cannot access the hive. Clearly label each package with your name.
3. Send hives to be sterilised with gamma radiation. Currently the only commercial service for gamma radiation sterilisation in Queensland is Steritech.

Dip hives in a hot wax dipping unit and treat all other potentially contaminated items using option 1 or 2:

1. Heat wax to 160°C.
2. Immerse the entire hive in the hot wax for at least 10 minutes.

Heat sterilisation boxes are also an effective method of treating AFB infected hives, if constructed and used following the instructions provided by the Department of Agriculture and Fisheries.