American Foul Brood, what we can learn

The BeeHolder, Autumn 2013


American Foul Brood (AFB) is a Notifiable disease throughout the European Community and therefore has legal implications. You are required to contact your Bee Inspector directly if you are suspicious of any foulbrood disease in a colony. The colony will be inspected by a Seasonal Bee Inspector who will test on the spot or send a sample to the NBU laboratory for confirmation. Colonies infected with AFB have to be destroyed and equipment sterilised. A Standstill Order will be placed on the apiary, bees and equipment.

It is a sad fact that nothing in this life is simple. If we are not dealing with summers that fail to materialise, a spring that is so short that blink and you miss it, then just when you think that you have full control of your colony ‘the mite that shall not be named’ reappears to test your patience and your nerve. Now we are faced with another threat that has the potential to decimate* our hobby for years to come.

The presence of American Foul Brood [AFB] in a colony in Newtown is not trivial and the threat to all of our colonies in the area must not be taken lightly. This is a disease that has no realistic cure other than vigilance and diligence. We must be vigilant in identifying the presence of the bacillus in the young cells of our colony so that it can be dealt with at source and diligent by constantly observing good aseptic practice when we inspect our own hives or when visiting other apiaries

This is a disease of the young as it is transmitted by the nurse bees when they feed the larvae. However larvae cannot be infected later than 53 hours after the egg has hatched. The disease is caused by a species of bacteria (Paenibacillus larvae) which actively divides in the larvae and which also produces spores. It is the spores which are most likely to be transmitted between colonies. How and when the disease appears in the first place can be difficult to determine and can often be present without the Apiarist knowledge. Brood that are affected will die when the larvae are stretched out on their backs and after the cells have been capped. The capping will sink inwards and became moist and discoloured: usually chocolate or purple in appearance. Some of the capping will be uncovered by the nurse bees in an attempt to remove the dead brood. Any uncapped dead brood is infected and as it is now open to the hive so that spores can be spread to others in the hive or distributed around the hive by the natural movement of the bees. Spores germinate in the gut of the larva and the vegetative form of the bacteria begins to grow, taking its nourishment from the larva.  The vegetative form of the bacterium will die but not before it produces many millions of spores. Each dead infected larva may contain more than 100 million spores. There are no precise measurements but in a single infected hive an approximate average of just 35 spores per larvae will result in the death of 50% of the brood. We have to remember that whilst the active bacillus can be readily dealt with the spores are highly-resistant to desiccation, heat, and chemical disinfectants. If left untouched at least 95% of hives will weaken quickly and eventually die.

We also need to appreciate that the spores can remain virulent for more than forty years in combs and honey.

AFB can be transferred from one hive to another by spores attaching to the bodies of mature bees (which are not be affected by AFB) when they clean the cells. In turn, the bees spread the disease directly by drifting to new hives, or indirectly through contaminating common foraging sites. The overall effect of the disease is to deplete the young in the colony which weakens the brood and exposes the hive to robbing by other bees in the area who are thriving. The problem is then compounded because spores from the bacillus will be present in the honey they rob and once this is transferred to a neighbouring hive, the whole cycle starts again. The general view is that all hives within three [3] kilometres of the infected hive are at most risk. The only real cure that exists is to burn infected comb and scorch the hive (not an option if you have poly units) or preferably burn the hive and contents in a pit and start againImportantly, it is considered that the most common source of cross contamination is the beekeeper. We inadvertently spread the disease by not following a set pattern of infection control or failing to be observant and identify the presence of contamination and swapping infected combs in the apiary.

The last thing you want to do is to become another link in the chain and this is where your actions need to be considered.

It is imperative that after you have visited your hives, or someone else’s in the club, that you sterilise anything that you used during the inspection. This will include the hive tool, your gloves, and boots to exclude any possibility of cross contamination. A weak solution of household bleach should suffice for tools-but remember to rinse with clean water before using again in another hive, and for those of us who use leather gloves, try wearing ‘marigolds’ over the top so that you can clean them between sessions. The bee suit can be more of a problem as many do not have the facility to remove the veil. If you can then it should be cleaned between visits. If not then you may wish to seriously consider isolating your hive equipment and protective clothing and keep it close to the boundary of the apiary so that when you leave you do not spread contamination. Importantly, try defining a small area of your shed/garage/house where your kit ‘lives’ and does not come in contact with any other clothing. If you can manage it, this should include a pair of wellies/shoes that are only used for visiting your apiary.

You should also consider your route to the hive(s) and if possible create a set path to and from the area. By having a set route you can put down an absorbent mat that you can load with disinfectant so that when you go to and from the hive you will automatically step on the mat and sterilise the bottom of your boots.

 More detailed information about cleaning and sterilisation is available from defra.

Warren and Margaret Towns

* I think the last sentence of first para, “decimate our hobby for years to come” is a bit too strong and alarmist. The incidence of Foulbrood around England and Wales in recent years can be seen on Beebase. Although it’s been rare in Mid and North Wales it is quite frequently found in some other areas and I don’t think most beekeepers in those areas consider themselves “decimated”. The point is that with more awareness and better hygiene we should be able to limit or prevent reinfection and spread.                                 Paul Aslin, SBI