Go back - Click here to print this page

BeeData www.beedata.com

A BEEKEEPERS GUIDE TO THE FOUL BROODS

or

Healthy bees are happy bees

Let's face it - its all rather boring anyway all this stuff about bee diseases. At the end of the-day what beekeepers really want to know about is honey isn't it? Diseases are too academic - the bit stuck at the back of the book that no one ever bothers to read unless they have to. And it's never going to happen to ' our' bees after all? Diseases only happen to ' dirty' beekeepers don't they? However, to get the best out of any animals they must be in the peak of health. So, if you want honey you must know about diseases - not just as a textbook exercise but with a view to understanding how they affect your bees and what to do about it should you come across a problem. With this text I have tried to pull together information from many sources to offer serious beekeepers an insight into keeping their bees both healthy and happy.

Keeping bees productively requires many skills. One of these is the ability to 'read' the bees. In farming terms this ability would be called stockmanship. It is always difficult to explain the ideas of stockmanship. This is best learned by working with some one experienced - even then some people never get it. It is a skill primarily based on keen observation together with a thorough knowledge of what you are looking at. But looking is no good without seeing and seeing is based on knowing and understanding what you are looking at so theoretical knowledge is also important.

Bee diseases can be broadly divided into those that affect the adult bees (or adult bee diseases!!) and those that affect the larval stages (or brood diseases). The most important thing in all disease control is to be able to recognise what is healthy. If you don't know what is healthy it will be impossible to tell what is sick. The signs of illness can often be quite slight at first but of course, this is the time that any treatments are most effective or any spread can best be limited to avoid much heartache later.

Natural controls

In a honeybee colony bees are crowded together in a warm and rather humid hive environment that is just perfect for the breeding and spread of disease. It is a tribute to their natural disease control mechanisms that they suffer so little. Happily, diseases are usually rare but when they do happen they can cause serious ongoing problems for the beekeeper.

The natural controls that help bees resist the worst problems of disease are, as with all animals, a combined result of the work of their immune system, their biology, their behaviour and their environment. Many of the diseases and parasites have evolved together with the bees over the millennia. In general parasites have a vested interest in not killing their hosts - just pushing them as far as they need for their own survival and increase without extinguishing the 'goose that lays the golden egg'. In contrast, pathogens such as AFB or chalk brood can only sporulate once they have killed the larva they have infected. Others, such as EFB, live in a manner that is more like a parasite. Some viruses are not pathogenic at all except in the presence of a trigger factor - very often our old friend the varroa mite.

It is not possible in such a short space to give more than a flavour of the complex and subtle disease limiting mechanisms. Different pathogens challenge colonies in different ways. Individual colonies (in essence individual queens) vary in their resistance to the different pathogens and parasites they encounter. The aware beekeeper would do well to assess his bees for signs of disease resistance and hygienic behaviour as well as critically examining his own beekeeping methods and techniques which can act either to reduce or increase the incidence and spread of disease.

Strict sanitary conditions are an absolutely vital aspect of bees' health. Bees are obsessive cleaners - little mops and buckets always at the ready! They are constantly cleaning and preening both themselves and other workers. They even have a special antenna cleaning tool on their front legs. Foreign bodies and dead bees are removed with great alacrity from the hive and where this isn't possible they are covered in propolis to isolate them. Honey and propolis also have their own natural antibacterial activity and the supersaturated sugars characteristic of honey inhibit bacterial or yeast growth. Cells are carefully cleaned between brood cycles and bees are very reluctant to use cells that don't meet their hygiene standards. Cells containing foul brood scales will be ignored for as long as pressure for egg laying space allows. Perhaps surprisingly, wax moths can be the beekeeper's friend for they will rapidly break down the wax of an abandoned, possibly diseased, colony and render it unattractive or unavailable to other bees.

Bees can recognise larvae and bees that are sick very quickly and act to remove them from the hive. If infected larvae are ejected before the bacteria have time to proliferate or spread then sources of infection can potentially be removed very rapidly. Removal of diseased or damaged larvae gives rise to the pepper pot brood pattern which is one indication all is not well with the colony. Feeding or heavy nectar flows reduce the incidence of disease by diluting any pathogens present, alleviating stress on the colony and allowing a larva to survive where it would otherwise have died. (In cases of EFB this is not always an advantage to the colony for it is the one case where it actually perpetuates the disease by allowing the pathogen to spread instead of being removed from the hive - which shows how cunningly pathogens can exploit their niches). Heavy nectar flows also act to keep older infective adult bees away from the young bees in the hive and wears them out so they die away from the hive. All these processes will help to reduce the incidence of disease. Poor conditions and in particular restricted forage opportunities, poor weather or too many bees in one area, always exacerbate the virulence of any pathogen. In human terms we would call this stress. Vigorous queens and plentiful forage are essential prerequisites for healthy, productive colonies.

The bee's proventriculus is very effective at sieving out tiny particles and up to 80% of AFB spores can be taken out of circulation this way. There are a variety of antibacterial substances in the haemolymph of the bee and a bactericidal factor in the glands of nurse bees. As they age the larvae become innately more resistant to infection. There is some evidence that AFB and varroa can actually reduce the effectiveness of the bee's immune system thus increasing their virulence. Incidentally, there is also some evidence that some of the varroacides we use can also do the same. Bees and their pathogens and parasites are in a constant evolutionary struggle with each other to ensure their own survival. All this going on in your colony unnoticed in the main by the beekeeper! Its amazing the bees have any time to go out and collect us any honey.

HISTORY

Aristotle was the first to record the pathological manifestation of foul brood but the name was first referred to by Schirbach in 1796. Bonner in 1798 writes of 'An uncommon Disaster which sometimes, though rarely, happens to Bees'. In 1866 Neighbour describes losses by both Dzierzon and Langstroth and defines for the first time two types of foul brood 'one moist and foetid, the other dry and not contagious'. After Pasteur established the science of microbiology the causal organism of AFB was identified but it was much longer before the more complex aetiology of EFB was unravelled. In 1885 Cheshire and Cheyne published the first comprehensive work on EFB but believed it to be caused by Bacillus alvei which we now know to be a secondary invader. In 1912 White deduced the causal organism to be 'Bacillus pluton' but this wasn't accepted at the time. In 1949 Aleksandrova thought she had managed to cultivate the elusive Bacillus pluton but Bailey found this to be Bacillus euridice another secondary bacteria. It took until 1957 for the causal organism to be finally identified by Bailey. At the time it was called Streptococcus pluton but was later reclassified as Melissococcus pluton. While AFB was widespread in the UK before the 2nd world war EFB was rarely recorded. In 1936 Tarr records 13 cases of EFB diagnosed at Rothamsted in the previous three years compared with 104 of AFB. According to beekeepers who remember that time EFB was not widespread in England being particularly known in the New Forest in Hampshire. Pollination contracts and other migratory practices were less common than today. However, the war put pressure on food supplies and sugar was in short supply so beekeepers started travelling into the area for forage, probably heather, for winter stores their colonies becoming exposed to the disease as a result. After the war there were major changes in agriculture and increasing pollination work meant colonies were more likely to be moved around the country with the resulting spread of EFB. Even today in the traditional English fruit growing areas and Hampshire EFB remains a common problem.

NOTIFIABLE DISEASES

In 1942 the first Foul Brood Order controlled AFB and EFB but they only became notifiable in 1982 under the current Bee Diseases Control Order. There are THREE notifiable diseases at present, American Foul Brood (AFB), European Foul Brood (EFB) and Varroasis. 'Notifiable' means that if you think your bees may have one of these diseases you are required to inform the relevant government department. Statutory control of notifiable honeybee diseases rests with the National Bee Unit based at the Central Science Lab in York.

AMERICAN FOUL BROOD

Although it is horrible thing to happen to bees, it is a relatively simple problem to get rid of. Time and again you will meet beekeepers, who once they are brave enough to admit to ever having

had it, will say that it was only once many years ago. Because of the long term policy of destruction of diseased colonies it is now a relatively rare disease. Most beekeepers will go through their whole beekeeping career and never see it.

American Foul Brood is caused by the spore forming bacteria Paenibaccillus larvae. Typically the bacterial spore is ingested by the young larva along with its food. Once in the gut the spores germinate, invade the body tissue and multiply rapidly. Eventually the infection overwhelms the grub which dies of toxaemia usually in the propupal stage. Thus one characteristic of the disease is that it is most commonly seen in the sealed cell stage of brood development. Once enough cells are infected larvae will die more quickly than they can be replaced and the colony will gradually die out. AFB is unique in that it invariably causes the death of an infected colony.

Visible signs

When infected larvae die you will find typical dark, sunken, wet looking, perforated cappings. A reliable field test for AFB can be done with a matchstick pushed into a suspect cell. The decomposing larval remains pull out in the form of a glutinous rope when the match is withdrawn to give a certain indication of AFB. These larval remains eventually dry to form a scale that sticks very tightly into the base of the cell and which the bees find impossible to clean out. Bees are reluctant to reuse a cell that doesn't come up to their standards of cleanliness and will avoid it as far as possible. This, and the death of larvae before they emerge, means the brood often shows a patchy appearance called 'pepperpot' or 'pepperbox' brood although this can typify other diseases as well as AFB. AFB scales fluoresce under UV light and will curdle drops of milk within 40 seconds when mixed on a slide. Contrary to popular opinion smell is a very poor indicator of the presence of AFB.

Spread between colonies

AFB is spread between colonies by any means that allows infected bees, honey or comb to cross from colony to colony. Top of the list for spreadability comes robbing, closely followed by the beekeeper. A beekeeper should never do anything that encourages robbing. One of the most important 'nevers' is never put cappings or supers out for the bees to rob dry. This is really asking for trouble.

Beekeepers can be very effective at transferring disease from one colony to another through their manipulations, usually by moving infected comb. AFB spores are very resistant and can remain viable virtually indefinitely in dried scales - easily missed on blackened old comb. Give granny's offer of grandad's' old equipment a polite miss or sterilise it well and burn the comb! If you are making nucs or equalising brood or anything else that requires you to put comb from one colony to another think twice about the colony's health - are you sure it's OK?

Another 'never' is never feed honey other than your own. Even this isn't advisable if you have had disease problems in the past. I have come across beekeepers who, by giving a pot of honey as a Christmas treat, have infected a good colony. Funnily enough bees seem to do better on sugar syrup!.

Some beekeepers will not pick up swarms from unknown sources on the grounds that they pose a disease risk. They may do, but it is better that any disease risk is under your control than a pocket of infection in the wild somewhere. Swarms are best collected, isolated for six weeks and then checked carefully for disease. You can minimise the risk of AFB by hiving onto foundation and not feeding for the first three days. This allows the bees to use any infected honey for the production of wax where any spores will be locked away from harm. It will take six weeks for any signs of AFB to show up.

Don't think just because colonies are strong that they cannot have AFB. A weak colony that is dwindling or has died out from foul brood may be robbed by its larger, fitter, more aggressive neighbours. They in turn take back spores to infect their own colonies and begin the cycle once again. I very clearly remember the hives that had died out from unrecognised AFB. The beekeeper had seen robber bees going in and out of the hives and assumed he still had live bees. Every single colony in the immediate area, dozens, were infected with AFB that summer because of their robbing activity. You must be absolutely certain there is no possibility of transferring disease when moving combs between colonies.

Control and legality

AFB is a virulent disease and is taken very seriously throughout the world. It is subject to statutory control throughout the EU and is a notifiable disease in the UK.

In the UK colonies officially diagnosed as having AFB are compulsorily destroyed under the supervision of the local bee inspector. Hives and appliances are sterilised by blowtorch. Personally, I also like to give them a good wash afterwards as well using hot soapy water containing washing soda or disinfectant. I have become a great enthusiast for the liberal use of washing soda. Gloves, bee suits, hive tools, smokers etc. should all be carefully cleaned. The bee inspector follows up cases of AFB by inspections of all other bees in the local vicinity. Beekeepers can help protect their bees by making themselves known to the bee inspector.

Insurance

To help cushion all the misery and financial loss caused by AFB, insurance is cheap and well worth while - if only out of consideration for feelings of the BEE INSPECTOR - who may have to break the bad news to you. It not quite so bad if he knows the beekeeper has some insurance! DON'T underinsure or you will only get a proportion of total worth. Your local beekeepers association, bee inspector or the Bee Diseases Insurance (BDI) will advise.

Resistant bees

One sideline is the idea of developing resistant bees. There is no doubt that natural resistance (or conversely increased susceptibility) is a real feature of this disease. I have occasionally seen stocks where there are just one or two cells in the whole stock and have heard anecdotally of other colonies where this had been the case over a long period - several seasons. There may be reasons for this apart from natural resistance, but AFB resistance can be bred for selectively. However, a note of warning to add to the debate (as I am sure this suggestion will provoke some reaction) Naturally resistant bees may not necessarily make control of AFB easier. In fact it is likely to make it MORE DIFFICULT. Since a feature of resistance to AFB is NOT that the bees never get AFB just that they show it in fewer cells. The unintended consequence could be to make AFB much harder to find making resistant bees a low level infection source that is extremely difficult to detect.

EUROPEAN FOUL BROOD

EFB is a serious notifiable disease widespread in some parts of the UK. It can weaken or kill infected colonies and the causative bacteria can remain lurking unsuspected in colonies or comb for many years. Currently, when European Foul Brood is diagnosed two courses of action are possible - either destruction or treatment of the colony. Which action is taken depends on the level of infection and the likelihood of the colony responding to antibiotic treatment. The wishes of the beekeeper are taken into account where practical.


Visible symptoms

EFB usually affects unsealed brood killing the larvae before the cells are sealed. These larvae are quickly recognised and removed by the workers. This will cause the patchy brood pattern often called pepperpot brood. Pepperpot brood (or pepperbox brood as I have also heard it called) is not a sign of any particular brood disease but an indication that larvae are dying and a clear message to the beekeeper that he needs to find out why.

Rather than lying neatly curled into the typical 'c' shape, the EFB infected larvae moves into some unnatural attitude that I have heard described as 'lying uneasy in its cell'. The sick larva will look discoloured and 'melted' in appearance. Its gut will be filled with bacteria and this often shows through the larval skin as a white line. This contrasts with the normal yellow/orange/ brown of the normal larval gut. If you have never noticed this try looking closely at a larva next time you look in your bees. Finally the larva will die and dries up into a loosely attached brown flake or scale.

Microbiology of EFB

Simply put, European Foul Brood is caused by the bacterium Melissococcus pluton. This bacterium is carried from larva to larva on the mouthparts of the nurse bees. Cleaning bees mouthparts become contaminated as they polish the cells between brood cycles and the whole lot will be spread through the colony during the processes of grooming, food sharing and communication. Of course, diseases of all types can be spread between hives by robbing or drifting bees and the beekeeper also helps with colony manipulations, management practices and comb exchanges between colonies. Pollination, migratory beekeeping and sales of bees can spread diseases over a wide area.

Unlike AFB, where the bacteria are invariably found in pure culture because of the antibiotic released by the bacteria as they sporulate, the presence of secondary bacteria are another feature of EFB. ' Bacterium Acromobacter euridic' is most common and is thought to accelerate the death of infected larvae while Melissococcus faecalis (Sour brood) is characterised by its sour smell. Where EFB has become well established you may find the secondary bacteria Paenibacillus alvei also characterised by an appalling smell. When this is present larvae may die after the cell has been sealed giving rise to dark, perforated and sunken cappings resembling AFB. The vital difference is that, although the cell contents are brown and gooey, they do not form a decent rope when tested with the matchstick. They do however form rather sticky scales although these can be distinguished from AFB because of the variable colour and because they can be removed from the cell. The presence of these bacteria can indicate that the disease is of long standing and that antibiotic treatment is unlikely to be effective.

Practical consequences of biology

Melissococcus pluton is a sneaky little organism with one or two quirks that make EFB more difficult to diagnose and control than other bee diseases.

. The pathogen acts as a parasite competing with the larva for its food.

. When there is enough food infected larvae survive to pupate.

. Signs of disease are not always expressed although the bacteria remain within the colony.

These points have profound practical consequences for beekeepers.

The bacteria multiply in the mid gut of an infected larva where they compete for the larval food supply, in effect they act as parasites rather than pathogens. As long as there is plenty of food there will be enough to meet the demands of both the larvae and the bacteria. The developing larvae will survive and the colony won't show any outward signs of disease. However, if the available food is only just enough the bacterial competition will cause the larva to die of starvation and signs of European Foul Brood become obvious. The fact that the bacteria compete with the bee larva for food and if there are enough bacteria and not enough food, the larva will die of starvation is a very important point to bear in mind. Understanding this explains some of the difficulties that can arise in the detection and control of EFB. The age of the larvae at infection can also affect the development of the disease. Small inoculations of bacteria in older larvae will not have time to develop sufficiently for disease signs to show before pupation.

Bees remove sick and dying larvae from the hive, which consequently greatly reduces both the level of bacteria present and the numbers of larvae displaying clinical signs of disease. Perversely, it is the larvae surviving to pupate that ensure infective bacteria remain in the colony. The reason is rooted in the larval anatomy. Prior to pupation larvae have a blind gut - so stuff can go in but not come out. Bacteria may invade and develop in the larval gut but will not be released into the comb. As it prepares for pupation the ends of larval gut join allowing the contents to be voided into the cell and contaminating the comb with infective bacteria.

Two important practical consequences arise for the beekeeper from the interaction of bees and bacteria.

. It will not always be possible to see signs of EFB in the colony. This doesn't necessarily mean it has gone. It has a 'now you see it now you don't' reputation. As long as there is plenty of food coming in to the colony then there will be enough for both the larva and the bacteria to survive. In this circumstance there will be few, if any clinical signs. Remember too, it is the survival of infected larvae that perpetuates the disease. Where there is not enough food, e.g. at times of dearth or where there is rapid brood rearing and bees are only just able to keep up with demand for larval food, disease signs will show. The bees recognise the sick larvae and dispose of them outside the hive with their bacterial contamination still safely locked inside their blind gut. The clinical signs of disease will disappear and the levels of bacteria present will be greatly reduced. Disease signs may be obvious and widespread at one inspection but have completely vanished by the next. In fact this is one of the bees natural control mechanisms for this disease and demonstrates how closely the EFB bacteria and the bees' life histories are inter-linked and how comfortably this pathogen is adapted to its host. It also has consequences for the timing of antibiotic applications.

Once EFB has been present in a colony a reservoir of bacteria will remain in the comb with the potential for re-infecting the colony at a later date. The levels of bacteria in the colony will

rise and fall and disease signs may or may not show but there will always be some bacteria remaining unless the beekeeper intervenes to do something about it. This can occur even if the comb has been removed from the colony for a time. Professor Heath showed quite clearly that combs stored for several years can still contain viable EFB bacteria. It is this ability for sub-clinical levels of bacteria to remain in the comb that makes it so difficult for the beekeeper who is unfortunate enough to have European Foul Brood to control it - let alone get rid of it completely.

The best time to look for EFB, at least if you want to find it, is when brood rearing is at its maximum and food availability is only just sufficient for a healthy larva to survive and pupate. Remember that EFB bacteria act as parasites so, for an infected larva, there will not be enough food to go round, it will die and the disease signs will show up. This will usually be in late May or early June depending on the size of the stock and where you live. Inspections that are not timed to look in a colony when EFB symptoms are likely to be visible are useless as far as EFB control is concerned. It is also hopeless looking for EFB when there is little or no unsealed brood for instance when requeening or swarming has occurred.

Remember that even where there are no visible symptoms that the bacteria may still be present in the hive and is likely to be so if there has been a history of disease in the colony, the brood frames, or the area. It may be in a subclinical state or surviving as lurking bacteria waiting for the right conditions to show disease signs again. Bacteria in honeybee colonies can stay in this 'lurking' state for many years with no apparent ill effect on the bees and may show up when conditions are right as an apparently spontaneous outbreak.

Herein also lies another debate. Are the bacteria naturally ubiquitous in the environment and therefore normally present in every bee colony or are they only there after the colony has been infected with disease? Each of these ideas, or models, will have a different consequence for the practical beekeeper. If the bacteria is there in every colony what triggers the disease and how can we control it? If it is not ubiquitous but remains perhaps as a bacterial or subclinical infection after a disease outbreak then how do we get rid of it once and for all? Experiments from Cardiff University point to the bacteria being ubiquitous in the environment. In my own experience as a bee inspector (which is practical not scientific) I am not alone in believing that I have never seen a spontaneous case of EFB. There has always been a clear pathway of infection usually rooted in the history of the colony or the area.

ANTIBIOTIC TREATMENTS

. At present an important facet of EFB control is antibiotic treatment. I want to look at the way that the life cycle of the bees and the EFB bacteria interact with the use of antibiotics for treatment of bee diseases and some of the issues that may arise. Antibiotic treatment is NOT LEGAL in this country for use against AFB and is very strictly controlled for EFB. There are cogent reasons for this which I will endeavour to explain.

Terramycin

The treatment for EFB in this country at present is the antibiotic Terramycin (Oxytetracycline). This has been shown to be the most effective antibiotic for treatment of EFB. Other antibiotics tested in the past were either not as effective, were uncomfortably stable and persistent in honey or were too valuable in treatment of human diseases to use for animal ailments.

An important point to recognise is that Terramycin is a bacteriostat not a bacteriocide. This means that it does not kill the bacteria outright. The function of a bacteriostat is to control the numbers of bacteria present by curtailing their ability to reproduce. It prevents the existing bacterial population from increasing further. The natural disease control mechanisms of the host organism (in this case the bees) are then expected to overcome the infection and to restore normal health. Bacteriostats are simply an aid to re-establishing the effective operation of natural disease control mechanisms where these have been overwhelmed. This has consequences for practical beekeeping as it affects both the timing and usage of the antibiotic. It adds another dimension to the saga of the EFB/honeybee balance of power struggle.

One practical consequence is that timing of treatments is not always self-evident. Treating when symptoms show may not in fact be the optimum time. If you treat when disease is heavy then what you are basically doing is interrupting the cycle at the worst possible time. Back to our basic biology. I have explained how EFB goes through high and low points of infection. Consider the larval

anatomy and its effect on the disease cycle. When the disease is at high levels then the larvae that die are removed from the colony together with their bacterial load and infection levels are reduced naturally. However, if you put a dose of antibiotics in at this time then many larvae that would have died will survive. It is the larvae that survive that perpetuate the disease by evacuating their gut contents to contaminate the brood cells. This may in fact be encouraging higher levels of bacteria than doing nothing. Another reason why heavily infected colonies may be better destroyed.

Sometimes you hear someone pontificating about the joys of prophylactic treatment. Despite the fact that it is illegal, there is a body of opinion that considers this prohibition an inconvenient restriction on their beekeeping practice. So we will consider this scenario. Basically, antibiotics only really reduce the visible symptoms for a while and the disease lives to fight another day - now conveniently hidden from the beekeepers prying eyes. The antibiotic hasn't cured the disease only suppressed it. If there are no disease signs to enable the beekeeper to recognise the problem then there will be no way for a beekeeper to know if there is anything wrong with the bees. This may sound fine - after all you could say no signs of disease; no problem. However, the reality is hidden disease; big problem. You could compare it with taking an aspirin to treat a brain tumour - the headache might go away but the underlying cause still remains. Worse, with no signs to warn the beekeeper, the disease is likely to be widely spread as a result of normal beekeeping manipulations. Finally, there are increasing numbers of reports of Terramycin (oxytetracycline) resistance in honeybee colonies in parts of the world where it is routinely used against diseases. I have occasionally heard beekeepers bragging that they keep the diseases hidden from the bee inspectors and I often wonder who they are fooling most - the bee inspectors, their customers or themselves?

There are a variety of consequences of prophylactic or blanket spring antibiotic treatments.

.It is very easy for every colony the beekeeper owns to become infected with disease - because there were no signs to warn the beekeeper. If you stop using antibiotics disease will erupt so you are stuck on an eternal treadmill that is not easy to get off.

.Other beekeepers in the area who are not blanket treating will constantly have problems with disease since they will always have a local source of low level, undiagnosed disease which quickly expresses itself when it reaches untreated hives. In their turn they also form a reservoir of infection in the area to pass back those who are treating illegally.

.The signs of more virulent diseases such as AFB may also be suppressed - two brain tumours for the price of one!

.Bacteria can become resistant to antibiotics quite quickly especially if they are misused - which leaves you nothing to fight with should you really need it. There are also real concerns now about routine antibiotic use in food producing animals (this includes bees!!) contributing to the development of antibiotic resistant bacteria in the human population.

Consumers are, quite rightly in the light of recent major problems with our food supply chain, very concerned about the nature and means of production of their food. They don't want their food produced with routine antibiotics. UK honey is among the best in the world. We should be selling onto a gourmet market - especially if we are to get a price for our honey that reflects its production costs. UK honey must project a green image if it is to attract the premium prices it needs to be economic.

There are minor issues about treatments that are too much to go into in detail. Ideas about the amount of antibiotic used per application, the methods of application, the breakdown times of antibiotic residues and what it breaks down into are all areas that have been discussed, heatedly at times. These are topical issues that affect our food production at present. The 'chattering classes'- the ones that write to newspapers and buy our quality honey - are more discriminating than ever. The issues aren't just academic and I have tried to outline them as clearly as possible.

Common sense and disease control

One of the most basic challenges for the beekeeper is to minimise the risk of disease spoiling his colonies. AFB is easy, destroy the colonies as previously described and the problem will go away. EFB is more complex. As with everything in beekeeping there are no guarantees. However, beekeepers can help themselves enormously by taking some common sense, precautions.

A strategy for EFB control

Even if EFB can't be cured - and there are those who say it can - it can certainly be more effectively controlled. I would love to be able to say it is easy. It isn't. A number of very big obsta

cles stand in the way of this. Clearing stocks of EFB is time consuming and requires a SUSTAINED and METHODICAL effort possibly over several years. It also costs money which beekeepers have a reputation for being unwilling to part with. It is sensible to involve your local Bee Inspector in any plans you may have since they offer expert advice free of charge.

It may then be possible to plan the Terramycin treatment at the optimum time essentially at a time when signs of EFB are low or not showing and there have been few brood cycles. This will normally be in the spring. Ideally, one apiary would be designated as a 'hospital' or 'isolation' apiary. Here any stocks that have shown EFB symptoms in the past or are of unknown provenance would be collected together conveniently in one place for more careful inspection and management. This might also act to reduce the incidence of disease at other sites by removing potential sources of infection. The terms of current legislation do not allow the movement of diseased bees except under licence.

There is increasing evidence suggesting that shook swarm techniques can play a very effective part in controlling EFB. This is logical since it is known that brood combs from infected stocks will constitute a substantial reservoir of infective bacteria. People who have tried this technique are usually pleased with the extra yields and vigour they get from the colony. Shook swarms are best done in conjunction with contact colony treatment with neighbouring apiaries also being considered potential contact colonies. Supers need to be fumigated before reuse and should ideally only be used on the same colony. Failing that it should be kept in the same apiary. If you have a hospital apiary then suspect supers should be used there. Scrupulous hygiene is essential. Stress factors such as moving bees should be avoided and obviously it is unwise to use combs or colonies with a history of infection for making your increases.

Technical details

Contact colony treatment

At present contact colony, or spring treatment is only available under specific circumstances set out in the MAFF Advisory leaflet Statutory Procedures for Controlling Foul Brood. It must be carried out before May 31st and is only available for larger apiaries where there is a considered need. Under no circumstances will antibiotics be used in apiaries where AFB is also present because of the risk that AFB symptoms will be masked by the treatment. In this case all EFB infected colonies will be destroyed.

Shook swarm frame changes

Antibiotic treatment only suppresses the disease signs with the larva for a limited period of time and does not affect the bacteria in the comb or hive parts. Subsequent use of contaminated equipment or comb from hives that appear healthy (and this may be due simply to the antibiotic treatment masking symptoms) facilitates and continues the spread of disease.

Changing comb by shaking the bees off and giving new foundation or techniques such as the Bailey frame change have long been practised as an aid to the control of diseases. For diseases where a significant residue of the pathogen remains in the comb common sense dictates that changing the comb at an appropriate time of year will give the colony a better chance of getting over the problem. Anecdotal evidence at present suggests it is possible to reduce EFB infection levels dramatically by carrying out comb changes using a shook swarm technique and most people who have tried it (even without the use of antibiotics) have been very pleased with the results. Comb changes should only be undertaken in late spring/early summer to give the colony sufficient opportunity to draw out the comb and build up the colony to full strength and colonies need feeding well in order to draw out the new comb especially if the weather is poor. Contaminated brood combs should be burned. Where EFB has been of long standing it is likely that at will be present sub-clinically in every colony in an apiary so changing combs in the whole apiary may also have to be considered an option.

In some countries the shook swarm technique is used to control AFB. However, this is a much more virulent pathogen and the risks of re-infection from the honey carried by the bees in a shook swarm are too great and the time and the economic savings are too minimal for this technique to be particularly worth while. Back to insurance and vigilance as the keys here.

Assessing the risk of disease problems in your area

. Honeybees in some parts of the UK run a much higher risk than others of contracting European Foul Brood (EFB).

Where any disease is locally prevalent beekeepers need to be particularly vigilant. Beekeepers buying bees or equipment from problem areas obviously run a greater risk of finding (and worse - spreading) disease in subsequent years. Contact your local bee inspector when planning to buy bees. Colony inspections for brood disease are free and no reputable seller will object to a brood inspection.

Regular inspection

. Regular inspection of brood combs is an essential aid to early diagnosis of disease. The sooner disease is found and dealt with the less chance it has to spread to other colonies and the more likely it will be only a light infection. Light EFB infections are more likely to respond well to treatment - on the old adage basis of stitches in time. Beekeepers should feel confident that they are able to recognise healthy sealed and unsealed brood. If you can recognise what is healthy will you be able to see when all is not well. However experienced you are never be afraid to seek a second opinion. Field inspection, diagnosis and advice regarding bee health problems is available free of charge to all beekeepers from The Central Science Labís National Bee Unit inspection service.

Apiary hygiene

. A fundamental aspect of any disease control programme is good apiary hygiene. This encompasses everything from collecting brace comb to ensuring that old combs and equipment are not left scattered about the apiary. Cappings, supers and honey buckets should never be left out for the bees to rob clean. Anything that excites the bees to rob will encourage the spread of disease. Having convenient collection and storage systems in place allows beekeepers to make good apiary hygiene an integral and easy part of their inspections. Human nature dictates that if a thing is convenient to do then it is more likely to get done.

Hygiene of clothes and equipment

. Bee suits and gloves should be washed regularly. This has the added bonus that the smell of stings from the last apiary visit will be washed away rather then remaining to excite the bees next time you go.!! Rubber washing up gloves or plastic beekeeping gloves are easier to keep clean than the more expensive leather gloves - so you can save money and take the moral high ground as well. Disposable gloves are very useful especially when working in an apiary where there is a known infection - there is often a handy supply at the garage diesel pump! Methylated spirits and washing soda are very effective for removing wax and propolis from equipment and gloves. Hive tools etc. should be flamed from time to time. If disease is found while working special care should be taken to thoroughly cleanse all beekeeping equipment before going to another stock or apiary.

Colony manipulations and management

. Comb from colonies with a history of EFB should never be used to make up nucleus colonies or for any other beekeeping manipulations that require comb to be moved from one colony to another. This is a guaranteed way to spread any lurking disease bacteria between colonies. Swarms may also carry infection and some beekeepers refuse swarms on these grounds. However, it is much better, for beekeepers to take responsibility for stray swarms than let them take up residence in the wild where they may become a disease reservoir for all the bees in the area. If they are unwanted they can be destroyed. Otherwise, to reduce the risk of disease, swarms should be isolated, hived onto clean foundation and not fed for 3 days. This allows any honey that the bees have brought with them to be utilised in wax building and so removed from circulation along with any spores or bacteria it might have carried.

Moving stocks

. Bees that are moved are at greater risk. A combination of circumstances contributes to this. There may be disruption of their natural disease control mechanisms. They may be mixed with other stocks of bees that carry disease and bring it back to the home apiary. Bees moved out to the heather or pollination contracts should ideally be returned to their original site. A removable colour coding will enable the appropriate apiaries to be easily identified.

Isolation apiaries

. Where possible bees that have shown EFB symptoms in the recent past should be kept on an isolation site once the standstills have been removed. This allows all potentially problematic colonies to be dealt with in one place. It is not advisable to use these colonies for migratory purposes or use the comb or bees to make up nucleus hives etc.

Super combs

Where bees have been infected with EFB care should be taken with super combs that have been in contact with the infection. The use of these combs should be limited to the stock from which they were removed. For large-scale beekeepers this is unlikely to be a practical option. Under these circumstances supers or top bars could be colour coded or otherwise marked for use in the same apiary. Where there is a history of EFB, it is possible (but not proven) that sterilisation of super comb will reduce potential for infection by this route. There are two possibilities - fumigation with acetic acid and comb irradiation.

Acetic acid kills EFB bacteria very effectively in the laboratory but it has not been tested under field conditions. However, it also gives benefits for other problems such as nosema and some wax moth stages. Fumigation with acetic acid is a simple procedure. Super combs can be treated in the stack with 100 mls of 80% acetic acid on cotton wool pads or towelling placed between each super in the stack. The combs must be dry and acetic acid is more effective under airtight conditions. Some beekeepers use plastic bags for comb storage and this would give a suitable environment for comb sterilisation It may also be possible to make a purpose made sterilisation unit. Combs should be aired well before use to remove any the remaining acetic acid fumes.

For beekeepers working on a large scale, particularly where there are serious ongoing problems with EFB, it may be worth considering irradiation of combs. To all intents and purposes this is 100% effective for killing bacteria. It is possible to have comb irradiated at two units in the UK. The cost is reduced if purpose designed containers are made to maximise the number of combs that can be irradiated at one time.

Storage

When hives are taken out of use for a while it is good practice to clean and sterilise the component parts before storage or reuse. Scorch hive bodies or wash them with washing soda or other disinfectant. Steam cleaning is particularly effective if you have access to it. Excluders can be scrubbed using hot, soapy water and washing soda. Do not attempt to flame excluders - zinc ones burn and wire ones may be distorted. Some beekeepers like to put the excluder in the solar wax extractor for a brief period to soften wax and propolis before washing. For the very particular, frames can be cleaned once the comb has been removed by boiling them in washing soda or dishwasher powder. Its worth the effort - they come up looking really nice. An old washing machine or Burco type water boiler can be adapted for this.

Safety

Acetic acid is corrosive and must be handled with care. Use proper protective clothing, do not inhale fumes and avoid splashes. Any contact with the eyes or skin should be washed immediately with copious amounts of water and medical attention sought if necessary. Glacial acetic acid is acetic acid at 100% concentration. To dilute to 80% acid use 4 parts acid to 1 part water. Always add the acid to the water. Acetic acid is corrosive and will cause rust to form on metal hive parts. People with sensitive skins may react to washing soda or detergents so wear gloves and take care when handling chemicals.

It is essential that beekeepers take proper safety precautions when handling acidic or caustic materials

NEW IDEAS

Genetic resistance or susceptibility

Very little research has been done in this area but it is not unreasonable to expect that some bees will show a greater disease resistance than others. It may be worth while for beekeepers to consider their records and observe any signs of greater susceptibility or increased resistance and to plan their queen rearing and replacement accordingly. There is also a renewal of interest in hygienic bees and their ability to control disease.

Biological control

There are radical new ideas in the pipeline about biological control of EFB which may revolutionise the way we control EFB. However, it is a long way from commercial reality and in any case disease treatments should never become a substitute for knowledge and good husbandry.

SUMMARY

Healthy bees are happy bees - and productive ones. Vigilance and a bit of common sense will help avoid major problems with disease and allow the beekeeper to get on with the enjoyable parts of beekeeping.

Learn to recognise healthy bees then you will know what is sick.

Make health checks part of your routine inspections.

Practise good apiary hygiene.

Arrange your apiary to minimise drifting bees.

Avoid practices that causes robbing.

When you practise any manipulation be sure the all the colonies involved are healthy.

Collect up stray swarms so they cannot form pockets of infection elsewhere.

Avoid old comb.

Use your local bee inspector as a resource. They are there to help, believe it or not, and are all

expert, practical beekeepers themselves.

Keep your insurance up to date.

AFB

1. AFB is a disease of sealed brood

2. Larvae die of toxaemia

3. Scales remain infective for many years

Signs

1. Dark, sunken, wet looking, perforated cappings

2. Roping of infected cell contents

3. Sticky, irremovable scales form from larval remains

4. Pepperbox brood

5. Colony spirals into decline and death

Control

Destruction is the most economic and effective method

EFB

1. EFB is a disease of unsealed brood

2. Larvae die of starvation

3. Signs are most obvious at times of peak brood rearing or minimum honey flow

4. Signs will NOT show if there is enough food for both bacteria and larvae to survive

5. Bacteria can be present in the hive even if there are no symptoms showing.

Signs

1. Larvae discoloured with loss of surface detail

2. Pepperbox brood

3. Larvae lie ëuneasy in the cellí

4. Heavy bacterial load makes the larval gut appear white

5.In well established cases there may be roping and smell caused by secondary bacteria.

Control strategy

1. Isolate stocks with a history of infection

2. Time treatments appropriately where possible

3. Treat contact colonies including any closely neighbouring colonies if possible

4. Keep supers for designated colonies or apiaries

5. Change brood comb from diseased colonies using shook swarms

6. Fumigate stored comb with acetic acid.

7. Maintain high standards of apiary hygiene

8. Minimise stress (for bees and beekeeper)

P.A.M. Pam Gregory March 2000

Go back - Click here to print this page