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Bee Health
Bee Brood Diseases
What might come as a surprise to new hobby beekeepers is the realisation that bees are being threatened by diseases, pests and parasites.

Some diseases affect the brood, i.e. brood diseases - other diseases affect the adult bee population, i.e. bee diseases.

Regular monitoring of colony strength, pests and diseases is a vital element of successful beekeeping.
Bee Brood diseases are caused by fungi, bacteria and viruses and can affect both sealed and unsealed brood. In their dormant form brood diseases can exist in virtually every beehive, or are just waiting outside.

However, a strong and vigorous bee colony does not easily get affected, it is mainly when the colony weakens that diseases become an issue.

The identification of brood diseases by their symptoms can be challenging and confusing, and some publications do in fact add to the confusion.

This publication by the Agriculture Victoria, AG0990 A Guide to the Field Diagnosis of Honey Bee Brood Diseases, is a field guide for apiarists to identify the four important brood diseases: American foulbrood, European foulbrood, chalkbrood and sacbrood.

An excellent reference is a publication from the Queensland Department of Agriculture and Fisheries, where under the title "Chalkbrood" the confusion around the identification of brood diseases is clarified.


Healthy Brood appearance
In general, the appearance of a healthy brood pattern is regular with no dead larvae or pupae. When capped, each cap is slightly raised or convex, without any holes. Caps are uniformly brown, tan or cream.  Note: the empty cells in between the capped are "heater cells" and not a sign of a problem.

Larvae are glistening and pearly white. Healthy pupae under the caps are at first white but as they develop into adults, their colour darkens. The eyes begin to colour first.
Below: Healthy capped brood (Pupae)
Healthy capped brood
Below: Healthy uncapped brood (Larvae)
Healthy uncapped brood

Common brood disease symptoms
A symptom common to all bee brood diseases is perforated cell caps, or cell caps completely opened or removed.

It is an indication that something is wrong with the capped brood.

Some publications describe this as a symptom for AFB, but don't panic, this symptom is common to all issues resulting in dead brood behind capped cells, even chilled brood that died without a disease.

When the expected hatching of bees from the pupae is overdue the adult bees start opening some of the capped cells to investigate.

Below: Perforated capped cell - opened by the bees to investigate.
Perforated capped cell

Brood Disease Management
Detection
Hive Examination - Examination of brood frames and floor debris is required especially in spring. Bees should be gently shaken from the frames to allow full inspection, abnormalities are then easily spotted.

Monitoring
Vigilance is important with all honeybee diseases. Check all colonies regularly for health and suspect any colonies that are not thriving where there is no already known reason. Colonies that die out should be examined thoroughly and sealed to prevent robbing and spread of any disease present.

Controls
Diseases have a more serious effect on weakened colonies. Prevention is the best method of controlling diseases by maintaining healthy, strong and vigorous colonies that display good hygienic traits.



Chalkbrood - a bee brood disease caused by a fungus
Chalkbrood is a very common disease of honeybee brood caused by a fungus Ascosphaera Apis and it affects both sealed and unsealed brood. The fungus grows through the bodies of infected larvae sending fine vegetative thread-like growths into the larval body tissues, eventually overcoming and killing the larvae after its cell has been sealed.

Chalkbrood is generally present in the majority of honeybee colonies at one time or another. The spores of Ascosphaera Apis can be present in a hive and have no apparent effect on it. It is generally not considered a serious disease and the effects on colonies are only slight. However, colonies that are already weakened by other circumstances may suffer to a greater extent, especially in early spring.

Our references:


Possible Causes
Research on Chalkbrood indicates that the causes are not conclusive - some reporting "humid and cold" while others report "warm and dry" weather conditions.

Detection
Hive Examination. Examination of brood frames and hive floor debris is required especially in spring. Bees should be gently shaken from the frames to allow full inspection, abnormalities are then easily spotted. Chalkbrood 'mummies' are easily seen and may even fall out of the cells during examination.
Below: Chalkbrood mummies in comb cells
Chalkbrood in comb
Below: Chalkbrood mummies in comb cells
Chalkbrood in comb2
Symptoms
Chalkbrood symptoms may be mistaken for other brood diseases, such as American foulbrood (AFB), sacbrood, European foulbrood (EFB) or even white pollen. However, once identified there is no mistaking the appearance and consistency of larvae affected by chalkbrood.

At first, larvae are covered with a fluffy white fungal growth, like white mould on bread or very fine cotton wool. Larvae become swollen inside the cell. Later, the dead larvae dry out to become hard, white or grey/black chalk-like mummies.

Below: Chalkbrood mummies removed from cells
Chalkbrood removed from cells
Below: Chalkbrood mummies in front of hive entrance
Chalkbrood in front of entrance

Recognition
The infected larvae take on the hexagonal shape of the cell before shrinking, at which point the adult bees will remove them from the comb. Remains are noticeable on the hive floor or at the hive entrance, looking as they have been mummified.


Method of Chalkbrood Infection
Chalkbrood spores are highly infectious. The disease spreads as the bodies of dead larvae release millions of sticky spores which adhere to hive components and adult bees. These spores are known to remain dormant and infectious for 15 years or more.

Chalkbrood spores are most commonly transmitted by:
  • Beekeepers - Transferring contaminated equipment and material between hives, colonies and apiary sites.
  • Contaminated pollen, by infected foraging bees leaving spores at floral and water sites, by queens, drifting bees and drones.
  • Robbing - Colonies weakened by Chalkbrood will fall prey to robbing, transferring spores to other colonies and apiaries.
  • Drifting - as with Robbing will transfer spores to other colonies.
  • Swarming - Swarms can carry the spores with them to new sites where the disease can spread once new brood is produced.
Note: Beekeepers are the principal and most rapid means of spreading Chalkbrood Disease.

Treatment
There is no specific treatment recommended for Chalkbrood. The disease has only slight effect on otherwise healthy colonies but may have a more serious effect on weakened colonies. Prevention is the best method of controlling this disease by maintaining healthy, strong and vigorous colonies that display good hygienic traits.
  • Hives with Chalkbrood can generally be recovered by increasing the ventilation through the hive.
  • Colonies that suffer excessively from Chalkbrood may need to be re-queened.

Recovery
Hives with Chalkbrood can generally be recovered by:
  • removing "mummies" from bottom boards and around the entrance
  • destroying combs containing large numbers of "mummies"
  • supplying new frames with foundation
  • providing good ventilation in hives
  • warm hive location - low lying, cool apiaries are typically more prone to chalkbrood
  • dry hive location - humidity can aggravate outbreaks of chalkbrood
  • adding young adult bees to hives
  • not allowing bees to winter in a hive that is over-supered
  • feeding sugar syrup, fresh uncontaminated pollen or supplements
  • maintaining strong hives by regular re-queening
  • reducing or preventing interchange of hive materials
  • not using the same site each year - if possible shift the apiary site slightly.
  • good hygiene - cleaning hands and equipment between hives.
  • change clothes and disinfect smokers, boots and hive tools between apiaries or infected hives.


Sacbrood - a bee brood disease caused by a virus
Sacbrood is a relatively common disease and does not usually cause severe colony losses. It is commonest during the first half of the brood-rearing season and can often exist unnoticed affecting only a small percentage of the brood. In a healthy colony adult bees detect and remove infected larvae very quickly. Normally by the time the beekeeper spots the symptoms the disease has become too severe for the adult worker population to handle.

Our references:

Causes
Sacbrood disease is caused by the Morator aetatulas virus. Remains of larvae that have recently died are yellow in colour and are highly infectious. Larval remains more than two months old, are brown and dry, and not infectious.

Detection
Hive Examination. Examination of brood frames is required especially in spring. Bees should be gently shaken from the frames to allow full inspection, abnormalities are then easily spotted. Adult bees will perforate or tear down the cell cappings with dead larvae content.

Recognition
  • The larva lies fully extended on the bottom of the cell with its head characteristically raised in a "gondola or banana" shape towards the top of the cell.
  • Darkening begins at the head - later spreading to the rest of the body.
  • The skin of the dead larva changes into a tough plastic-like sac. Between the skin and larval body a greyish granular fluid accumulates.
  • Body segmentation is maintained in the dead larva.

Below: Sacbrood
Sacbrood
click on picture to open link to source
Symptoms
Infected brood dies soon after being capped but before changing to pupae. When first affected, larvae are dull and grey in colour. They then turn slightly yellow with a dark head and become brown after a few days, eventually turning almost black. Head development of diseased larvae is typically retarded.
The 'gondola or banana' shape of dead larvae is characteristic of this disease. During the period of decay, the outer skin of the dead larva toughens. The larva can be easily removed intact from the cell with a pair of tweezers. The name sacbrood refers to the appearance of the watery and granular remains enclosed in the tough skin. If a large amount of brood becomes affected, the colony is weakened. Bees appear reluctant to remove dead material from the cells and the queen is forced to lay elsewhere in the hive.

Method of Sacbrood Infection
Nurse bees transmit the virus when they feed larvae with brood food from their hypopharyngeal glands.
The virus may survive up to four weeks in larval remains or in honey or pollen.

Sacbrood is also transmitted by:
  • Beekeepers - Transferring contaminated equipment / material between hives, colonies and apiary sites.
  • Robbing - Colonies weakened by Sacbrood will fall prey to robbing, transferring the virus to other colonies and apiaries.
  • Drifting - as with Robbing will transfer the virus to other colonies.
  • Swarming - Swarms can carry the virus with them to new sites where the disease can spread once new brood is produced.
Note: Beekeepers are the principal and most rapid means of spreading Sacbrood Disease.

Treatment
There is no specific treatment recommended for Sacbrood. The disease has only slight effect on otherwise healthy colonies but may have a more serious effect on weakened colonies. Prevention is the best method of controlling this disease by maintaining healthy, strong and vigorous colonies that display good hygienic traits.
  • Hives with Sacbrood can generally be recovered by increasing the ventilation through the hive.
  • Colonies that suffer excessively from Sacbrood may need to be re-queened.

Recovery
Hives with Sacbrood can generally be recovered by:
  • destroying combs containing large numbers of infected larvae
  • supplying new frames with foundation
  • providing good ventilation in hives
  • warm hive location - low lying, cool apiaries are typically more prone to health threats
  • dry hive location - humidity can aggravate outbreaks of diseases
  • adding young adult bees to hives
  • not allowing bees to winter in a hive that is over-supered
  • feeding sugar syrup, fresh uncontaminated pollen or supplements
  • maintaining strong hives by regular re-queening
  • reducing or preventing interchange of hive materials
  • not using the same site each year - if possible shift the apiary site slightly.
  • good hygiene - cleaning hands and equipment between hives.
  • change clothes and disinfect smokers, boots and hive tools between apiaries or infected hives.


EFB or European Foulbrood - a bee brood disease caused by bacteria
European Foulbrood (EFB) is a brood disease of honeybees caused by the bacterium Melissococcus plutonius. The disease is endemic throughout eastern Australia, but is not known to occur in Western Australia. European foulbrood is less deadly to a colony than American foulbrood. Melissococcus plutonius does not form spores, though it can overwinter on comb. Symptoms include dead and dying larvae which can appear curled upwards, brown or yellow, melted or deflated with tracheal tubes more apparent, and/or dried out and rubbery.

EFB is highly contagious with all stages of larvae development. Worker, drone and queen bee larvae are all susceptible to EFB infection. Larvae are most susceptible to infection when they are less than 48 hours old, and usually die while still in the coiled state and before the cell is capped. In cases where larvae die after their cell has been sealed, the cap may be perforated, sunken, concave and dark.

European Foulbrood is often considered a "stress" disease, a disease that is dangerous only if the colony is already under stress for other reasons. An otherwise healthy colony can usually survive European foulbrood. Prophylactic treatments are not recommended as they lead to resistant bacteria. Poor nutrition and severe stress, e.g. insecticide poisoning, often cause this disease to break out.

Our main sources:
AG0990 A Guide to the Field Diagnosis of Honey Bee Brood Diseases by Agriculture Victoria

European Foulbrood by Queensland Department of Agriculture and Fisheries

Wikipedia
Below: European Foulbrood EFB
EFB

Treatment
The 'Shook Swarm' technique of bee husbandry can be used to effectively control the disease. With this method an artificial swarm is created by shaking all bees from the EFB infested combs onto new foundation frames and let the colony start building from scratch. The infested combs are removed and destroyed.


AFB or American Foulbrood - a bee brood disease caused by bacteria
Internationally, American Foulbrood (AFB) is the most serious, contagious bacterial disease of honeybee brood. It is caused by the spore-forming bacterium Paenibacillus larvae.

AFB can appear and spread quickly through a colony. If left untreated it can kill the colony very quickly.

Early detection of the disease is important because routine apiary management and interchange of hive components can easily spread it to healthy bee colonies. The spores can remain viable for at least 40 years and can remain dormant on beeswax combs, used hives and components, honey, wax and propolis. They are very resistant to heat, direct sunlight, dehydration, fermentation, chemical disinfectants and veterinary drugs.

AFB affects unsealed and sealed brood - young larvae, less than 24 hours old, are most susceptible to the infection.

AFB is one of the most serious bee brood disesases and has to be dealt with without delay.

The Livestock Disease Control Act 1994 requires that anyone who knows or suspects that AFB is present in his/her apiary must notify a DEDJTR apiary officer within 12 hours. Failure to notify is to break the law.

If AFB is confirmed, the bees must be killed and the hive and equipment either burnt or irradiated.

You can have your hive and equipment irradiated by Steritech.

For more details check out these references:

Agriculture Victoria:
 

DPI of NSW: American Foulbrood   and   Wikipedia

Detecting AFB
Although there are numerous publications and illustrations of how to determine that the brood disease you just discovered is in fact American Foulbrood, the symptoms are not always conclusive. At least in its early stage it could be easily mistaken for some of the other brood diseases, even for an experienced beekeeper.

A picture tells a thousand words - even more when it is a moving picture...
The Department of Primary Industries of New South Wales has published a very useful series of Video Clips on their website and on YouTube to assist beekeepers with the conventional method of  identifying AFB and its eradication. >>watch these clips>>

However, the conventional method is not always conclusive and only a laboratory test can remove any doubt. This requires time, taking a sample on a glass slide and sending it to the laboratory and waiting a few days for the results to return. Gribbles Veterinary Australia is the point of contact for submission of samples.


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