American Foul Brood (AFB)

American Foul Brood is a highly destructive bee brood disease caused by the bacterium Paenibacillus larvae. Spores germinate in the mid gut of young larvae through contaminated food. Larvae younger than 24 hours are more susceptible to infection. Once the brood cell is capped, the infected larvae usually die in a short period of time. The vegetative bacterium will also perish; however it will first produce millions of spores that spread throughout the hive, continuing the cycle. One of the most devastating aspects of AFB is its resilience, as it can remain viable for up to 80 years in honey and on beekeeping equipment.

Symptoms

The first visible signs of AFB are usually spotty brood patterns and holes in the capped cells that appear jagged or off-center. Capped cells can also appear sunken or ‘deflated’. American Foul Brood will emit a strong, unpleasant odour. Larval Scale, where the decomposed lavae appear as a dried ‘scale’ on the cell wall, along with Pupal Tongue, are distinct signs of AFB.

Control

Hives and equipment infected with AFB must be destroyed by law in the EU and in most states of the U.S.A.

In most countries, the disease must be reported immediately.

Diagnosing American Foul Brood

European Foul Brood (EFB)

Though considered less serious than American Foul Brood, EFB is a brood disease caused by the bacteria Melissococcus plutonius. Larvae consume the pathogen via food, which then enters the digestive system and takes nutrients from the developing larvae. Larvae then die before the cell is capped. There is also evidence linking the transmission of EFB to the bite of the Varroa Destructor mite (Kanbar and Engels 2003). As Melissococcus plutonius is not a spore forming bacteria, it is spread throughout colonies by robber bees and by contaminated honey and equipment. European Foul Brood is found in all continents that keep European honey bees and has been of particular concern in Switzerland, continental Europe, the UK and the U.S.A. Though colonies usually recover, it has been linked to colony collapse in severe cases.

Symptoms

European Foul Brood is most common in spring when brood rearing is at its strongest. The first sign of EFB can be a patchy and uneven brood pattern. Infected larvae will turn a yellow brownish colour and appear twisted or contorted. Like AFB, the decomposing larvae emit a strong, sour odour. Year on year EFB can occur due to the presence of Melissococcus plutonius spores on contaminated honey, foundations and equipment.

Control

Mild EFB can be treated with OTC antibiotics, or the shook swarm technique. Requeening can also assist in cleaning out the colony. However if EFB is beyond treatment, colonies and equipment should be destroyed.

Please note that the use of antibiotics may be restricted in certain countries and that you should always follow the national guidelines.

Chalkbrood

Chalkbrood is an infectious disease of the brood caused by the Ascosphaera apis fungus. The disease infects the gut of larvae and causes them to dry out and harden, turning white or grey in colour. The fungus is usually introduced to the hive by forager or robber bees.

Symptoms

The earliest sign of Chalkbrood is a white, cotton like substance covering the brood. As the infestation worsens, the substance will darken. The ‘mummified’ corpses of infected larvae can often be found at the hive entrance, placed their by worker bees demonstrating cleaning behaviour.

Control

Increasing ventilation throughout the hive will help to stop the spread of the Ascosphaera apis fungus. Replacement of combs and frames can help with more severe cases, as can requeening.

Typical chalkbrood flying board

Sacbrood Virus (SBV)

Sacbrood virus is a disease caused by the Morator aetatulas virus. The virus is most common in worker brood larvae, which they catch via feeding from adult nurse bees. The virus multiples within the infected larvae, causing strange behaviours such as sitting up in the cell with their heads protruding. The larvae cannot shed their endocuticle, which gradually collects fluid and appears as a liquid filled sack. The Larvae will die before the cell is capped. The corpse will gradually harden, before becoming a brittle scale that sticks to the cell wall. Though not as damaging, adult bees younger than 8 days old can also be infected. Though they show no symptoms, they pass on the virus to the next generation. Sacbrood Virus is found the world over and is most common during spring and early summer.

Symptoms

The most visible indicator of Sacbrood, is the presence of dead or dying brood in a ‘canoe’ like shape. As the virus spreads, worker bees will become reluctant to clean out infected cells. This leads to spotted and irregular brood patterns.

Controls

There are no chemical treatments for Sacbrood Virus. Maintaining strong colonies is the best way to mitigate infection, as is using thoroughly cleaned equipment and combs. Requeening can be a way to treat severely infected colonies.

Deformed Wing Virus (DWV)

Deformed Wing Virus is an RNA virus with several sub-types, such as Varroa Destructor Virus 1, Kakagu Virus and Egypt Bee Virus. Deformed Wing Virus is found in colonies with heavy varroa mite infestations. The mites parasitize the pupae, causing deformed wings as well as other body malformations in the adult bees. DWV is linked to colony collapse, as symptomatic bees have a severely reduced lifespan.

Symptoms

The most visible sign of DWV is the shrivelled, paralysed wings of the infected adult bees, as well as shortened, rounded abdomens. Strong varroa mite populations are also a pre cursor to the virus, as varroa are not only a vector for the virus, but are believed to act as a replicating incubator.

Control

The most effective way of controlling Deformed Wing Virus is to control varroa mite infestation. To learn more about varroa mite practices, check out our free guide.

A bee with deformed wings caused by DWV

Nosema disease (Nosemiasis, or Nosemosis)

Nosema disease is a disease caused by the microsporidian fungus Nosema Apis or Nosema Ceranae. Nosema spores invade the midgut epithelial cells of adult honey bees and are spread by neighbouring bees through faecal matter, or through food exchange. Both versions of the disease negatively decrease productivity and survival of honeybee colonies by stunting the development of the fatprotein body as well as the levels of proteins and fatty acids in the bee haemolymph. Nosema disease is prevalent throughout Europe and North America, and Spanish scientists have linked Nosema disease to colony loss.

Symptoms

It is not easy to detect in the early stages of the disease, as symptoms usually develop later. Defecation near or inside the hive entrance during winter is a sign of N. apis infection, as is the presence of a milky coloured midgut in heavily infected bees. There are no visible signs of N. cerenae infection. Colonies affected by N. apis generally display low levels of infection during summer, then a small growth period in autumn, that will peak in winter. N. cerenae is more consistent throughout the year.

Control

Good beekeeping practices are the best prevention, such as setting up non-humid, ventilated apiaries and ensuring correct wintering measures. Low infection levels will not necessarily mean the loss of a colony, as long as conditions improve before it spreads. However, there are currently no generally accepted treatments for Nosema disease.