American foulbrood

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American foulbrood disease (AFB) is prescribed as restricted matter category 1 under the Biosecurity Act 2014.

AFB is a highly contagious, fatal bacterial disease affecting honey bee larvae and pupae. It can reduce hive productivity and lead to hive collapse and death. If not controlled, it can lead to large numbers of infected or dead hives.

You must take all reasonable actions to:

• minimise the incidence of AFB in your apiary
• prevent the disease from spreading to other apiaries.

Cause

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

Distribution

AFB has been detected in all states and territories in Australia. The prevalence of the disease varies by region and can change over time.

Life cycle

The pathogen has 2 stages:

• The reproductive (vegetative) stage is an active stage in which bacteria multiply inside the infected bee larva.
• The resting (spore) stage is a dormant, highly infectious stage in which the bacteria form the spores that transmit and spread the disease. 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).

Animals affected

• European honey bees (Apis mellifera)

Clinical signs

Early signs

In the early stages of infection, the diseased larvae or pre-pupae turn slightly yellow. As decomposition progresses, the infected larvae or pre-pupae become coffee-coloured and slump lengthwise along the bottom of the cells.

When infected larvae are probed with a matchstick or similar tool at this stage, the contents of the cell may repeatedly rope out, forming a fine elastic thread up to 30mm long.

Later signs

As the infection advances, the diseased larvae or pre-pupae turn dark brown and dry into a hard scale that adheres tightly to the lower cell wall. Good lighting is needed to see the scale, as it closely matches the dark colour of older brood combs.

If death has occurred during pupation, a partly developed pupal tongue may protrude as a fine thread projecting upwards towards the top of the cell.

In the advanced stages of infection, the brood pattern has a patchy, irregular ‘pepperbox’ appearance.

Cappings, if present, will be either:

• perforated (often with off-centre, jagged pinhole-sized perforations)
• or
• dark, sunken and greasy in appearance.

Similar disorders and AFB diagnosis

Signs of the following disorders are similar to those of AFB:

• parasitic mite syndrome
• sacbrood
• European foulbrood
• disappearing disorder (also known as ‘the muck’).

To have a diagnosis of AFB confirmed, send samples to the Biosecurity Sciences Laboratory.

How it is spread

AFB can spread through:

• natural bee behaviour such as
  • robbing
  • drift
  • swarming

• beekeeper activities such as
  • interchanging bees and hive components
  • feeding
  • poor hygiene practices.

Tips to minimise spread

To reduce the chance of spread by these methods, follow these tips.

Robbing

Robbing occurs when bees from 1 colony invade another to steal food stores. To prevent robbing:

• Reduce the number of hive entrances.
• Keep all equipment and hive waste strictly bee-proof and closed.
• Feed bees sugar syrup during nectar shortages.

Drift

Drift occurs when bees lose their orientation and mistakenly enter a neighbouring hive instead of their own. To prevent drift:

• Break up uniform, straight rows of hives.
• Arrange colonies in irregular patterns, facing entrances in different directions.
• Use distinct paint colours, symbols or natural landmarks to give foragers clear visual navigation cues.

Swarming

Swarming is a colony's natural method of reproduction. To prevent or reduce swarming behaviour, provide timely hive space:

• Add supers (honey boxes).
• Split strong colonies.
• Replace old queens.

Interchanging bees and hive components

To avoid introducing infected bees or hive components:

• Only introduce bees, brood and queens from inspected, disease-free sources.
• Avoid or reduce swapping of frames.
• Label equipment for each hive.

Feeding

Using contaminated honey or pollen can spread infection. To avoid this:

• Do not feed your bees honey or pollen unless it has been sterilised using gamma radiation.

Poor hygiene

Poor apiary hygiene can spread infection. To avoid this:

• Sterilise all borrowed gear before use.
• Disinfect equipment and tools after each use.
• Maintain a strict barrier system.

Risk period

AFB spores can lie dormant in hive materials and equipment for 50 years or more. Extensive decontamination methods, such as irradiation or burning, are needed to kill AFB spores.

Reinfection happens when larvae are fed contaminated food. Young larvae (less than 24 hours old) are most susceptible to the infection. Infection can develop in both unsealed and sealed brood.

Monitoring and action

Check your hives regularly for AFB. Good practice is to check:

• every 6 to 12 weeks
• when you remove or insert frames or equipment
• when you move materials between hives.

You will need:

• protective clothing
• a hive tool
• a smoker
• a matchstick
• a small clean plastic jar or paper towel (for collecting and submitting samples)
• a sealable plastic bag
• decontamination equipment.

Method

• Open the hive by removing the lid, supers (honey boxes) and queen excluder. Place them to the side of the hive.
• Remove the frames from the bottom box (brood box) 1 at a time—use the hive tool to loosen them if necessary.
• Check each frame for the queen and gently replace the frame she's on before checking others. If you can't find her, you can still inspect the brood.
• Once you have a brood frame, shake the bees off the frame back into the same box so you can see the brood clearly.
• Closely examine at least 3 brood frames for any signs of AFB.
• If you see signs of AFB, poke a matchstick into a suspect cell, swirl it around and pull it out slowly. If thick, ropey brown material sticks to it, you are likely to have a brood disease or disorder and you should collect and submit a sample for testing. Follow the guidelines for submitting samples.
  • Place the matchstick in a clean plastic jar or cut a 10cm by 10cm piece of suspect comb (without honey) and wrap it in paper towel.
  • Place the jar or wrapped comb in a plastic bag and seal it.
  • Place the plastic bag in a padded postal bag or a small sturdy cardboard box.
  • Send the matchstick or comb sample to the Biosecurity Sciences Laboratory.
  • Enclose a completed specimen advice sheet for bee diseases.
  • Ensure no live bees are sent with the sample.
• Decontaminate all potentially contaminated items, such as your hive tools and smoker.
• Report positive findings to:
  • Biosecurity Queensland on 13 25 23
  • or
  • the Exotic Plant Pest Hotline on 1800 084 881.

Control

There is no treatment for AFB.

If your colony has AFB, you must prevent the spread of the disease to minimise its impacts on your remaining hives, neighbouring apiaries and the wider industry. To do this, follow these steps:

• Euthanise the infected colony.
• Secure and then destroy or decontaminate any potentially contaminated items.
• Implement barrier systems.

Euthanise bees in infected hives

Wait until evening when all the bees have returned to the hive from foraging. Then close the hive entrance and complete the steps shown for 1 of the following options.

Any bees that escape when you are working through your chosen option will cluster at the original hive site. Check back after an hour and bag any remaining bees, then seal the bag and freeze it.

Option 1: Freeze

• Smoke the honey super to drive the bees down into the brood box. Shake any bees that may remain in the honey super into the brood box.
  • Place the brood box with bees inside a large garbage bag.
  • Alternatively, bang the brood box firmly down into an upturned lid to dislodge the bees, then transfer the bees into a large garbage bag .
• Seal the bag and freeze it for 48 to 72 hours.

Option 2: Spray or submerge

• Add dishwashing liquid to a bucket or large tub of water until the water is visibly soapy, then follow 1 of these methods:
  • Shake the bees into the bucket.
  • Spray the bees directly using soapy water in a spray bottle.
  • Submerge the brood box and bees in the large tub.
• All bees must be wet at once.
• For more information, refer to Australian Pesticides and Veterinary Medicines Authority permit PER90262 (PDF, 100KB).

Option 3: Use petrol

• Use unleaded petrol to euthanise bees.
• Refer to Australian Pesticides and Veterinary Medicines Authority permit PER92753 (PDF, 112KB) for detailed instructions.

Secure potentially contaminated items

Until potentially contaminated equipment can be destroyed or decontaminated, keep it tightly sealed and inaccessible to bees. This equipment includes:

• hive components removed from the infected hive
• tools used on the hive
• protective clothing used while handling the hive.

Destroy or decontaminate potentially contaminated items

Destroy or decontaminate all potentially contaminated items. This includes:

• infected hives
• hive tools and other tools (such as knives) that you used on the contaminated hive
• other beekeeping tools (such as smokers)
• other items from hives (such as beetle traps)
• protective clothing worn while working with infected hives.

Every worker should disinfect their hands, shoes and clothing. Wash protective clothing and boots in hot soapy water and then soak them in a bleach solution.

There are 3 options for decontaminating or destroying other items that may be contaminated with AFB spores.

Option 1: Burn and bury

This option can be used for wooden hive components and hive materials such as honey, comb, propolis and dead bees. However, do not use a fire pit for metal tools and hiveware or for plastic hiveware.

1. Ensure that you have a fire permit if required.
2. Check that no fire bans are in place.
3. Dig a pit in soil. Make the pit large enough to contain all hive material and to allow for complete burning.
4. In the pit, light a hot fire and burn the wooden hive components and hive materials.
5. Bury the remnants of all burned material at a depth of at least 30cm. Ensure all material is thoroughly covered.

For metal tools and hiveware:

1. Remove all honey, wax and propolis.Burn and bury the removed material.
2. Extensively scorch the tools and hiveware with a blowtorch to kill AFB spores. (Alternatively, soak the tools and hiveware in a bleach solution.)

You do not need to bury the metal tools or hiveware after burning or soaking them.

For plastic hiveware:

1. Remove all honey, wax and propolis. Burn and bury the removed material.
2. Soak the hiveware in a bleach solution or send it for irradiation (option 2).

You do not need to bury the plastic hiveware after soaking or sterilising it.

Option 2: Sterilise using gamma radiation

This option can be used for wooden, metal and plastic hive components and beekeeping equipment, such as hive boxes, frames, smokers and tools .

1. Ensure all equipment is free from honey, bees, small hive beetles and brood. If you do not do this, additional charges may apply .
2. Burn and bury any removed material that cannot be sent for irradiation (see option 1).
3. Wrap the hive components and any equipment in thick plastic. Ensure the plastic is tightly sealed so bees cannot gain access to the hive components and equipment. Clearly label each package with your name.
4. Send the hive components and equipment to be sterilised with gamma radiation. Currently the only commercial service for gamma radiation sterilisation in Queensland is Steritech.

Option 3: Dip in paraffin wax

This option can be used for wooden and metal hive components and beekeeping equipment.

Treat all other potentially contaminated items by sterilising or burning.

1. Place paraffin wax in a dipping unit and heat it to 160°C.
2. Immerse the hive boxes or components in the hot wax for at least 10 minutes.

Implement barrier systems

A barrier system divides a beekeeping operation into isolated, marked units. Restricting the movement of hives, components and tools between these units will help to contain any outbreak to a single group.

Follow these steps:

• Visually mark all gear by numbering or colour-coding and keep it within the designated units.
• Use site-specific equipment—dedicate each hive component to a single unit.
• Disinfect all equipment and footwear before moving to another unit.
• Use dedicated quarantine sites—monitor new or sick hives in an isolated yard.
• Visit clean hives or apiaries before visiting sites that have a history of pests or disease. That is, move from low-risk sites to high-risk sites, not from high-risk sites to low-risk sites.

Further information

• Read the Australian honey bee industry biosecurity code of practice (PDF, 14.2MB).
• Find out more about barrier systems.
• Learn more about American foulbrood.
• Read about the legal requirements for beekeepers.