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Bee Health
Diseases of the adult bee population
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.
Please note that in their dormant form almost all honeybee diseases can exist in any hive, 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.

Therefore, diseases can predominantly be found in hives where the bee population is low or has declined in numbers.

Adult Bee Diseases

Nosema Apis - a serious bee disease caused by a fungus

Nosema Apis has been discovered on Western Honeybees in 1909. It is the most common and widespread, serious bee disease directly affecting adult honeybees, including queen bees. In some years nosema may cause serious losses of adult bees and colonies in autumn and spring.

Nosema apis can wipe out entire bee colonies within a short time.

Nosema Apis is classified as a fungus and the dormant stage of nosema is a long lived spore resistant to temperature extremes and dehydration.

Nosema spores can be found in bees at any time of the year in varying numbers. Most hives have some nosema spore numbers, but clinical signs and adverse effects only occur when the hive is stressed. Then spore numbers escalate quickly resulting in dead bees, a restless, weak colony and dysentery stains on the hive floor, entrance and walls.

Fortunately, serious nosema outbreaks do not occur every year. In these epidemics, strong colonies may be seriously weakened before winter. They may be reduced to the size of a nucleus colony in a matter of days.

Infected colonies that survive the winter may require a long build-up period for the population of adult bees to reach normal numbers.

Our main references are:
AG0300 - Nosema Disease of Honey Bees by the Agriculture Victoria

Nosema Disease by the Queensland Department of Agriculture and Fisheries

Nosema Disease by the NSW Department of Primary Industries

Possible Causes
The following conditions appear to be associated with serious autumn outbreaks and epidemics of nosema:
  • heavy summer rainfall
  • early autumn break during the fine weather about mid-March to early April
  • working grey box (Eucalyptus microcarpa), red ironbark (Eucalyptus sideroxylon) and white box (Eucalyptus albens).
  • Caucasian honeybees Apis mellifera caucasica are reportedly less resistant to nosema than bees of the other strains.

Defecation in the hive and signs of unusual faeces on the outside of the hive is the most common indication of Nosema Apis disease present. Comb covered with brown freckles are another indication. However, examination of adult bees using a light microscope is the only reliable method of diagnosing the presence of spores of nosema.
Below: The presence of nosema disease shown by yellow/brown stripes and dots at the hive entrance.
Nosema on hive
Below: Brown freckles on otherwise white comb, mainly on the cell edges, indicate the presence of nosema disease.
Nosema on comb
Common symptoms for Nosema can be:
  • Restless, weak colony and dysentery stains on the hive floor, entrance and walls.
  • Dysentery stains as brown freckles on comb (easy to recognise are brown freckles or brown cell edges on new, white comb).
  • The worker bees are most severely effected, frequently crawling, rather than flying, due to dislocated wings.
  • Large number of dead bees close to the hive entrance.
  • Infected nurse bees lose the ability to produce royal jelly.
  • A high proportion of eggs laid by the queen of a infected colony may fail to produce mature larvae.
  • Young infected nurse bees cease brood rearing and turn to guard and foraging duties usually undertaken by older bees.
  • Life expectancy of infected bees is reduced due to the reduced utilization of pollen. In spring and summer, infected bees live half as long as non-infected bees.
  • In the case of an infection of the queen bee it comes to a degeneration of her ovaries and her egg production drops. As a result a supersedure of the queen is released in the colony. If this happens during bad weather the new queen does not get fertilized and becomes a drone producing queen.
  • Infected queens cease egg-laying and die within a few weeks.
  • Flight inability (“crawler”) can occur due to disjointed wings.

Bees infected with nosema can also show none of the common symptoms, or none that are specific for this disease. Many of the symptoms attributed to nosema disease also apply to other diseases or conditions of adult bees.

Preventive management practices
Management practices that reduce the stress on hives also reduce the number of nosema spores. Maintaining strong healthy colonies has been demonstrated to reduce the effects of nosema.
Management practices which may reduce the effects of nosema disease are:
  • Maintain colonies with queens with good egg-laying potential. Colonies prepared for winter should have a good population of young bees.
  • Ensure colonies have adequate supplies of high protein pollen in autumn. This will help to ensure good populations of young bees.
  • Ensure hives prepared for winter have good supplies of honey.
  • Place the hives in a sunny position in the cooler months of the year.
  • Choose apiary sites that have good air drainage and protection from cold winds. Avoid cool shady and damp sites.
  • The level of nosema infection can be reduced by placing the hive in a sun trap where it obtains maximum sun and maximum shelter from cold winds.
  • Maintain winter colonies in a minimum of hive space so they are compact and warm. Remove supers (boxes) of combs not required by the bees.
  • Avoid colony stress which can be caused by excessive opening of the hive, manipulation of combs, feeding and relocating colonies.
  • Avoid stagnant water sources which may become contaminated by dead bees and bee excreta.
  • Minimise the number of squashed bees during normal hive management. Any infection will be spread when their remains are cleared away by hive cleaning bees.
  • Replace old, dark brood combs to lower the number of spores in the hive, although this will never totally eliminate the disease. Many beekeepers remove two or more old combs from the brood nest each spring, replacing them with sheets of beeswax foundation.

Method of Nosema Infection
Infection does not normally pass directly from infected bees to the next generation of adults. Instead, young bees become infected when they ingest spores as they clean contaminated  combs.

During the summer months most honey bee colonies carry a few infected bees with little or no apparent effect on the colony. Spores may also persist on the combs. As the weather in autumn changes, these spores may initiate an outbreak of nosema. Losses  of bees at this time of the year may be very heavy.

Winter losses can also be heavy. Infected bees confined in their hives due to bad weather may defecate inside the hive soiling the combs and hive interior with excreta and spores. This, together with spores produced in the preceding autumn causes infection  in spring.

Spring outbreaks usually begin in late August or September, when temperatures begin to rise. They may last until late spring or early summer.

When the warm weather comes, the disease begins to decline due to improved flight conditions. The source of infection is largely removed because the bees are able to defecate outside the hive thereby reducing the contamination of combs.

Nosema spores are most commonly transmitted by:
  • Beekeepers - Transferring contaminated equipment and material between hives, colonies and apiary sites.
  • Contaminated honey or pollen.
  • Robbing - Colonies weakened by Nosema will fall prey to robbing, transferring spores to other colonies and apiaries.
  • Drifting - as with Robbing will transfer spores to other colonies.
  • Research reports indicate that worker bees can transmit nosema to queens in queen mailing cages, queen banks and queen mating nuclei.

Beekeepers are the principal and most rapid means of spreading Nosema Disease.

  • Prevention is the best method of controlling this disease by maintaining healthy, strong and vigorous colonies that display good hygienic traits.
  • Nosema spores cannot be killed by freezing contaminated comb.
  • Heat treatment in 49°C for 24 hours can be used to kill the spores on contaminated equipment.
  • Hives with Nosema can generally be recovered by thoroughly cleaning the hive and removing contaminated comb from the hive.
  • When hive and comb are heavily contaminated it is best to transfer all bees into a clean hive by shaking bees onto new frames with foundation  only - this should only be done when there is a strong flow of nectar and pollen and the colony can recover from the food loss.
  • Colonies suffering excessively from Nosema Apis may also need to be re-queened.

Hives with Nosema can generally be recovered by:
  • thoroughly cleaning the hive, inside and outside
  • removing frames with contaminated comb (brown freckles on comb and frame)
  • supplying new frames with foundation
  • providing good ventilation in hives
  • warm hive location - low lying, cool apiaries are typically more prone to nosema
  • dry hive location - humidity can aggravate outbreaks of nosema
  • 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
  • good hygiene - cleaning hands and equipment between hives.
  • change clothes and disinfect smokers, boots and hive tools between apiaries or infected hives.

Nosema Ceranae - an extremely serious bee disease caused by a parasitic fungus

Nosema ceranae can wipe out entire bee colonies within a short time

In 1996 nosema ceranae was discovered on the Eastern Honeybee and in 2004 it has also been detected on the Western Honeybee.

Although our awareness of nosema ceranae is fairly new, it is now clear that nosema ceranae is not a new disease of the European honeybee. Nosema ceranae has been detected in bee samples collected in the USA in 1996 and in France in 2002.

To date nosema ceranae has also been detected in Australia, except for Western Australia and Tasmania.

Most of the symptoms and effects of nosema apis and nosema ceranae are similar - however, identification becomes difficult as both types of nosema often appear in conjunction. The most significant difference is how quickly they can cause a colony to die. Bees can die within 8 days after exposure to nosema ceranae, which is faster than bees exposed to nosema apis. AG0300 - Nosema Disease of Honey Bees

The two types of Nosema are being researched and results published - however, it gets complex and confusing trying to find conclusive answers; some symptoms might appear or not, or it is uncertain whether they are the symptoms of one or the other type, or both in conjunction.

The foraging bees seem to be affected the most. They leave the colony and are too weak to return, thus dying in the field. This leaves behind a small cluster and a weak colony, very similar to the symptoms of Colony Collapse Disorder (CCD).

Nosema ceranae has been associated with colony collapse disorder (CCD), a condition which has devastated the beekeeping industry in the USA through the loss of many thousands of hives. Some suggest that nosema ceranae is a major contributor to CCD, as the fungus is believed to have been widespread since 2006, when CCD first became a problem.

Of great concern by researchers is the fact that once nosema ceranae has been discovered in a country, within a short time it has outnumbered the instances of the less severe nosema apis infections; i.e. nosema ceranae spreads much quicker than nosema apis.

The disease patterns related to Nosema ceranae exhibits some distinctions:
  • The changes in the digestive system are substantially more serious than known from Nosema apis.
  • Classical symptoms are often missing, such as diarrhea and crawler.
  • Remarkable number of dead bees close to the hive, or others not returning - the continuous reduction of the number of bees of the colony can lead to the colony collapse in a very short time.
  • While Nosema apis occurs mainly in early spring and disappears when the weather warms up, Nosema ceranae tends to occur all year around.
  • Especially in winter some colonies die within a short time and the bees lay dead in the box or hives remain simply bee-empty.

Whether all these symptoms are related to this new form of the Nosema can currently not be clarified conclusively.

Our own observations:
August 2010 - after the long and wet winter we found two of our hives bee-empty; sufficient stores of honey and pollen, but not a single bee in the hive and no cells with signs of brood, just well polished empty brood cells - however, some cells contained eggs - and surprisingly the hives were free from wax moths. CCD or Nosema ceranae?

August 2010 - in another case we had queen supersedure during winter, resulting in a weak colony with plenty of drones and hardly any worker bees, due to a drone producing queen.

April 2011 - Bees crawling in front of a hive and away in all directions, only a few bees flying in and out. Within a radius of up to 10 metres you could find bees crawling on the ground. Inspection of the hive did not show any anomalities or signs of a disease. After one week the hive was bee-empty. CCD or Nosema ceranae?

Colony Collapse Disorder - CCD - a new and extremely serious bee health issue

Colony Collapse Disorder wipes out entire bee colonies within a short time

Possibly as the biggest threat of all, since 2006 Colony Collapse Disorder (CCD) has had a devastating impact on bee numbers all around the world, mainly in the USA and some European countries. Research has gone into this phenomena and to date there is not yet a conclusion what exactly causes this disappearance of the bees. Findings indicate that the immune system of bees affected by CCD is weakened and they become volnerable to fungi, bacteria and viruses. Bees seem to loose their orientation and don't return to their hive - within a few days the beehive is rendered bee-empty. The causes of this syndrome are not yet fully understood; the proposed causes include environmental change-related stress, malnutrition, pesticides, inappropriate beekeeping methods, genetically modified (GM) crops, etc.

The following articles are an indication of the status:
30-April-2013, BBC News - Neonicotinoids banned in Europe The European Commission will restrict the use of pesticides linked to bee deaths by researchers.

Several publications indicate that Neonicotinoids are the main contributing factors for CCD, the neonicotinoid Imidacloprid is currently the most widely used insecticide in the world.

15-Mar-2012 International Business Times - Bee Colony Collapse Disorder Linked To Corn Insecticide

13-Jun-2012 - The Harvard Study on imidacloprid and CCD

The symptoms of CCD are:
Especially in winter or early spring hives remain simply bee-empty, without signs of any of the known bee diseases.

Our own observations:
August 2010 - after the long and wet winter we found two of our hives bee-empty; sufficient stores of honey and pollen, but not a single bee in the hive and no cells with signs of brood, just well polished empty brood cells - however, some cells contained eggs - and surprisingly the hives were free from wax moths. CCD or Nosema ceranae?

April 2011 - Bees crawling in front of a hive and away in all directions, only a few bees flying in and out. Within a radius of up to 10 metres you could find bees crawling on the ground. Inspection of the hive did not show any anomalities or signs of a disease. After one week the hive was bee-empty. CCD or Nosema ceranae?

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