Vets dispensing Oxytetracycline hydrochloride to beekeepers for European foulbrood

European foulbrood

European foulbrood (EFB) is a disease of honey bee brood caused by the bacterium Melissococcus plutonius. Diseased honey bee colonies can become weak and are unsuitable for honey production and pollination of crops.

M. plutonius may be present as sub-clinical populations in hives that show no signs of EFB. It is probable that most, if not all, honey bee colonies in Victoria carry latent infection.

EFB usually first appears in hives in Victoria in early to mid-spring. Development of the disease can be very rapid. It may only take several days after the first symptoms are seen for a large proportion of larvae to be infected.

Most diseased larvae fail to develop into adult bees and this causes rapid downsizing of the colony. Not all infected colonies die. Usually there is little or no warning of an impending outbreak and even good beekeepers may find the disease is in an advanced state and treatment must be applied immediately.

This scenario is often exacerbated by the fact that hives may be hundreds of kilometres from the enterprise's home base and inspections of brood at such locations may be at weekly or even greater intervals.

The slow natural recovery from EFB causes colonies to be unproductive for an extended period resulting in economic loss for the beekeeping enterprise.

Natural recovery is assisted by the occurrence of warm weather and improved conditions for bee foraging in late spring and early summer. Some beekeepers prefer to relocate diseased hives to an area sheltered from prevailing winds and with a good source of pollen.

While this may assist with a more rapid recovery, it may not remove the need to treat infected colonies to restore them to productivity in the quickest time possible.

Oxytetracycline hydrochloride (OTC) and approved products

This antibiotic is a prescription animal remedy (PAR) and the only treatment approved by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for control of EFB.

Vets must check that the  chemical products listed on this page are still registered for use with the APVMA prior to dispensing.

Only the following 4 products are registered for treatment of European foulbrood disease in honey bees:

• Broodmix
• CCD OTC 10 soluble powder
• CCD OTC 100 soluble powder

Some beekeepers have difficulty calculating and precisely weighing the amount of product and carrier in the proportions stipulated on the product label. Use of premixed products helps to prevent potential over- or under-treatment of hives.

OTC is applied in powder form to the brood nest of hives. Application of OTC in sugar syrup was practiced in the past, but OTC products currently registered for control of EFB have the following label statement: DO NOT USE as a wet treatment of bees.

A wet treatment can cause residues in honey that exceed the current maximum residue limit (MRL) set by Food Standards Australia New Zealand of 0.3 ppm of OTC in honey.

Dr Bill Bailey, author of 'Honey Bee Pathology' and EFB expert, advocated treatment of hives with OTC as early in the season as possible — before the time EFB symptoms are usually seen.

This prevents multiplication and accumulation of M. plutonius and decreases the severity of outbreaks in spring — or prevents them entirely.

Understand the beekeeper's enterprise

Before dispensing OTC for the management of EFB, veterinary practitioners will need to know the:

• number of apiaries owned by the beekeeper
• number of hives in each apiary
• beekeeper's brood disease management practices.

Beekeepers in Victoria must be registered with the department in accordance with the Livestock Disease Control Act 1994.

Beekeepers must:

• supply their current 'Certificate of registration as a beekeeper' which details the number of hives owned
• advise the veterinary practitioner of the number of apiaries (or yards/loads).

Without this certificate, the veterinary practitioner may not dispense OTC.

Dispensing OTC

Generally, veterinary practitioners will require confirmation that EFB is present in a beekeeper's apiary (or apiaries) to justify the dispensing of OTC.

On the first visit by the beekeeper to the veterinary practitioner, hives may not be diseased and there may be no records of disease from the previous season.

The beekeeper may however need a blanket or spot treatment as a preventative, depending on how the hives are managed. Provided the detailed documentation is supplied by the beekeeper, and they agree to record all details of OTC use, dispensing of OTC should be acceptable.

After blanket treatments have been applied, it may take several months before hives are affected with EFB again. At that time, the beekeeper must collect and provide appropriate material for diagnosis, or evidence of diagnosis, if additional OTC is to be dispensed.

The evidence can be:

• the provision of a laboratory report confirming EFB from a recently submitted bee larval smear
• the provision of a certificate from a department apiary officer after inspecting comb or a sample of comb with EFB diseased bee larvae
• inspection by the veterinarian of EFB diseased brood comb

If confirmation of EFB in hives is unavailable, OTC may be dispensed for all hives in an apiary for an early season blanket treatment, with enough to spot treat a few hives should there be a reoccurrence some months later.

At the time the disease recurs the beekeeper must collect and submit samples for diagnosis before veterinary practitioners can dispense more OTC.

If a blanket treatment is required later in the season (such as in spring) following an outbreak of EFB, then a sample must be provided by the beekeeper at that time. OTC can be dispensed once the sample has been received, with subsequent confirmation and advice to the beekeeper.

The same procedure applies for spot treatments.

The presence of EFB in one hive can be taken as presumptive evidence that M. plutonius is present in all (or the majority) of hives within the apiary. Accordingly, OTC may be dispensed for immediate treatment of all the colonies and ongoing spot treatment if EFB is detected during that season.

If there is no management of hives to avoid cross contamination between apiaries, it is likely that M. plutonius will be present in all the apiaries. The beekeeper may request sufficient OTC to treat all apiaries.

The degree of evidence to be supplied by the beekeeper to justify supply of OTC for the entire enterprise will be determined by the veterinarian in consultation with the beekeeper.

Treatment of hives on more than one occasion during the beekeeping year may result from environmental conditions (weather, nectar and pollen availability) and poor management of hives.

It could also be due to American foulbrood (Paenibacillus larvae) which is a notifiable disease, as well as other brood diseases and abnormalities. Reasons for breakdowns should be investigated before continued dispensing of OTC.

OTC record keeping requirements

Beekeepers must keep records as required under the Agricultural and Veterinary Chemicals (Control of Use) Regulations 2007 of all OTC used including:

• dates
• quantity
• number of hives
• which apiary is treated.

A copy of these records will need to be provided to the veterinarian for their records to support the quantity dispensed and used, and the basis of ongoing requirements for OTC.

Download the record keeping template:

• Treatment of bees or beekeeping equipment

Under the Agricultural and Veterinary Chemicals (Control of Use) Regulations 2007, veterinary practitioners who sell or use OTC to treat bees are legally required to make specified records within 24 hours of selling or using an OTC product.

Difference between American foulbrood and EFB

American foulbrood (AFB) disease is another endemic honey bee brood disease that invariably kills infected bee colonies. It is caused by the bacterium Paenibacillus larvae, which forms spores that remain viable for around 50 years and probably much longer.

The spores are found in honey and on the components of infected hives, as well as dead infected bee larvae and pupae. Notification of AFB outbreaks is required by the Livestock Disease Control Act 1994.

Infected colonies, bees and beeswax combs must be destroyed by burning. Hive components may be destroyed or sterilised by approved methods to render the spores non-viable.

EFB and AFB may occur simultaneously in a brood in the one hive — but never in a single larva.

More information can be found in A guide to the field diagnosis of honey bee brood diseases.

The application of OTC for control of EFB also has an effect on AFB by inhibiting vegetative growth of P. larvae. After application, the bees remove AFB infected individuals and the remaining brood shows no disease signs.

However, the spores in the hive remain unaffected, ready to initiate disease when the effect of the antibiotic wears off – usually after several months.

There is anecdotal evidence that some beekeepers treat AFB infected hives with OTC. This treatment is contraindicated on all four OTC products registered for control of EFB.

There is no mandatory requirement for beekeepers to provide evidence that their hives are free from AFB before OTC is supplied by a veterinarian for control of EFB.

The department encourages beekeepers to regularly check their hives for clinical symptoms of AFB and to submit samples of honey for laboratory detection of P. larvae spores.

Other resources

• Diseases of Bees – Agriculture Victoria
• A guide to the field diagnosis of honey bee brood diseases – Agriculture Victoria
• European foulbrood of honey bees and its control – DPI NSW
• Treating European foulbrood in Australian honeybees

Further information

If you require further information or assistance, please contact the Customer Service Centre on 136 186 or email: honeybee.biosecurity@agriculture.vic.gov.au

Glossary

Adult bee – fully-developed, bee after emergence from the brood cell.

Brood – honey bee eggs, larvae and pupae.

Brood nest, brood chamber – part of the hive in which the brood is reared. Usually refers to the lower section of multistorey hives, but may not be confined to just the bottom box.

Cell – an hexagonal compartment contained in brood and honey combs. Queen cells are peanut shaped.

Comb – comprises beeswax hexagonal cells constructed by bees on both sides of a midrib (or wax, or plastic foundation). Used to store pollen, honey and raise brood (hence honey comb, brood comb).

Larva (plural – larvae) – grub, the immature stage of the honey bee life-cycle immediately after hatching of the egg.

Super(s) – a box, or boxes, above the bottom box of the hive.