What is a sanitary transfer?

It is a beekeeping operation consisting of reducing a colony to the state of a bare swarm by placing it in a clean and fully disinfected hive (or nucleus box) containing only frames with foundation, without any addition of brood.

Why carry out a sanitary transfer? To rid the colony of the pathogen (the bacterium Paenibacillus larvae) and its highly resistant spores (contaminating elements), or at least to considerably reduce their pressure, by destroying all brood in which the pathogen multiplies as well as the materials and substances in which spores persist.

Under what circumstances must it be carried out?

Every beekeeper is required to comply with the specific sanitary regulations for American foulbrood once this disease has been diagnosed in the apiary. In particular, all weak colonies must be destroyed, even if they show only minor symptoms, as well as any severely affected colony regardless of its strength.

A transfer onto foundation must be carried out for any diseased colony provided that:

• it is only mildly affected,
• it is sufficiently populous,
• it has retained good vitality,
• the period lies between spring and early summer.

On what principles does the effectiveness of the transfer rely?

• During the two days following the transfer (the time required to build combs), bees eliminate most of the spores they carry on their bodies through intensive cleaning. These spores enter the digestive tract and are excreted with faeces at a sufficient distance from the hive. The sanitary fasting period, even if only partial (see below), promotes spore elimination.
• New food stores are therefore not contaminated, as they should only be stored a few days after the transfer.
• In the new hive, after reduction to the state of a bare swarm, a period of at least 4–5 days elapses before new larvae appear (after comb construction and resumption of egg laying by the queen), creating a sanitary gap. During this period, susceptible larvae—within which spores can germinate and the bacterium multiply in large numbers—are absent.
• Furthermore, adult bees (nurse bees) cannot contaminate larvae orally, as there are none present.

What conditions are required for a successful transfer?

• The colony must be strong enough to restart from the state of a bare swarm.
• The operation may only be carried out in spring and up to early summer: beyond this period, bees no longer have the capacity to rapidly build combs and accumulate sufficient reserves for winter survival. In addition, the risk of robbing is quite high at the end of summer.
• It must be carried out outside periods of heavy nectar flow: during strong nectar flows, bees are able to build both sides of a frame overnight to store their harvest. In this case, they do not have enough time to eliminate spores present in or on their bodies and may contaminate new stores.
• The transfer must be carried out during the day, placing the new hive exactly at the location of the diseased colony, so that foragers do not drift and contaminate the entire apiary.
• During the transfer, no brood frames must be added to the transferred swarm, so that for several days there are no susceptible larvae allowing the bacterium to multiply.
• Following the operations, at least two careful inspections at one-week intervals must be carried out on all colonies (transferred or not) in order to monitor any reappearance of symptoms (thorough brood examination) and the proper development of the swarms.

 

What equipment is required? Hive or nucleus box complete (bottom board, body, cover) and divider, clean and fully disinfected. As the colony is reduced to the state of a bare swarm, it is recommended to place it initially in a reduced volume: a nucleus box or a hive with divider. Frames with foundation in quantities adapted to the strength of the colony Large intact sheets of paper or cloths intended for destruction If necessary, a queen cage Disposable gloves (destroyed at the end of operations) or disinfectable gloves Usual equipment: smoker, hive tool, brush, protective gear (to be cleaned and disinfected after the transfer) Large, sturdy bags or boxes with lids to receive contaminated material prior to destruction (frames, papers, cloths, debris) and tools before cleaning and disinfection.

 

How is the transfer carried out?

• Smoke the affected hive.
• Move it 1–2 m forward, directing the entrance toward the original location (180° rotation).
• Place a hive or nucleus box equipped with frames with foundation at the location of the affected hive.
• Lay large sheets of paper or a cloth between the entrances of the two hives, fixing one end at the landing board of the hive to be repopulated so as to collect contaminated debris (and facilitate the bees’ entry).
• When possible, isolate the queen and place her in the new hive once some bees have entered, so that the rest of the colony follows more reliably.
• Shake or brush the frames of the affected hive one by one over the cloth so that the bees fall onto it and gradually enter the new hive.
• Burn the papers or cloths with the contaminated debris collected during handling, as well as all brood and food frames from the affected hive. Thoroughly clean and disinfect the hive body, bottom board and cover, as well as any equipment that may have been contaminated (brush, hive tool, smoker). Warning: take all necessary precautions to avoid any risk of burns or fire.
• Bury the burned residues in the ground.
• If burning on site is not possible, place all material to be destroyed in strong, airtight bags that will not tear during handling, so that no bees attracted by honey can access them. These can then be disposed of in containers or at a waste facility for incineration, or their contents can be destroyed by fire by the beekeeper in a secure manner away from the apiary.

Should feeding be provided after a transfer?

“The rule” is that transferred colonies should undergo a sanitary fast of approximately 48 hours and therefore should not be fed before this period has elapsed. This is feasible in the case of small operations or when the apiary is close to the beekeeper’s home.
Otherwise, when transferred colonies will not be visited again for about a week, feeding may be provided at the time of transfer, but the amount of syrup (50/50) given to the swarm should be limited to 0.5 or 1 litre depending on its population, so as only to meet the bees’ vital needs for a few days without allowing storage.

In conclusion:

Sanitary transfer constitutes a particularly simple method of controlling American foulbrood: it requires only standard beekeeping equipment and no medication. Despite its seemingly rudimentary nature, it has been used successfully for several centuries. Recommended as early as 1568 by a Silesian monk (Nikol Jacob) in his Treatise on Beekeeping, its effectiveness has since been regularly observed by beekeepers who have applied it while respecting all recommendations, and confirmed by scientists based on laboratory analyses showing extremely low spore levels in transferred colonies.

What other indications are there for a sanitary transfer?

Sacbrood and European foulbrood: when a large proportion of brood is affected but the colony remains sufficiently strong, transfer onto foundation with destruction of brood and food stores is necessary. The procedure is identical to that described above, but feeding can be more substantial and immediate. As in the case of American foulbrood, diseased and weak colonies must be destroyed.

Suspected contamination of wax and food stores by pesticides: in this case, transferring the colony onto new foundation or drawn frames aims to rid it of any toxic agents present inside the hive by placing it in a non-contaminated environment. Concrete cases carried out at the beginning of the beekeeping season have shown that this operation allows a good restart and good colony performance. Feeding can be provided as needed to help the colony resume its development.

Source: FNOSAD – National Federation of Departmental Beekeeping Sanitary Organisations

Photo credits: JM Hédon, JP Couix