3.1 - 3.5 - EFB

Question 1

EFB Cause

(MElissa Cockup Plutonis) remember mElissococcus for EFB

Starvation spiralling out of control to pepperpot smelling of melted candles losing scales

Answer 1

Caused by Melissococcus Plutonis bacterium
1 Bacteria multiply in the mid gut of infected larvae competing with the infected larvae for food

2 They remain in the gut (do not invade the tissue)
3 Larvae die because they have been starved of food
4 Normally occurs before the cells are sealed
5 A larva infected with EFB moves inside its cell instead of remaining in the normal coiled position characteristic of a healthy larva of the same age.
6 A larva dies in an unnatural attitude – twisted spirally around the walls, stretched out lengthways from the mouth to the base of the cell or across the mouth.
7 When EFB kills a high proportion of the larvae, the brood pattern often appears patchy and erratic as the bees remove dead brood and the queen lays in the vacant cells.
8 The gut of an infected larva may be visible through its translucent body wall. The mass of bacteria living within it give it a creamy white colour.
9 A very unpleasant odour may sometimes accompany severe EFB infection, depending on the presence of certain other species of bacteria in the remains of dead larvae.
10 As it collapses, a dead larva often looks as though it has melted, turning yellowish-brown and eventually drying up to form a loosely attached brown scale.

Question 2

EFB Cause

Answer 2

The bacterium responsible for causing the symptoms of European Foulbrood (EFB) is probably Melissococcus plutonius. When it infects a larva, other bacteria move in, causing secondary infections:

Paenibaccilus alvei
Enterococcus faecalis
Brevibacillus laterosporus
Lactobacillus eurydice

OR

• Bacillus alveri and laterosporus
• Bacterium eurydice
• Streptococcus faecalis

Question 3

EFB Progression of the disease

Answer 3

The bacteria enter a larva in brood food and multiply in the ventriculus (stomach), feeding on the larval food. The bacteria lodge between the peritrophic membrane and the food in the ventriculus. The bacteria act essentially as a parasite competing for food, and the larva dies of starvation about 3 or 4 days before the cell is due to be sealed. During this period the larva contorts itself into unusual positions, twisted spirally or flattened out lengthways in the cell.
Its colour changes from pearly white to cream and then to a yellowy green. The bacterial mass in the larval stomach causes much of this early colour change.

The supply of food to larvae affects the course of the disease. Because the bacteria compete with the larvae for food, increasing the supply of food can enable larvae to survive infection.

At the onset of nectar flow in early spring, the number of house bees recruited to forage may increase rapidly leaving fewer in the hive to feed larvae. Under these conditions, M. plutonius may be able to starve larvae to death and give rise to symptoms of the disease. When the ratio of nurse bees to larvae stabilises and larvae receive enough food to survive to pupation, symptoms disappear.
However, EFB can occur throughout a season and will sometimes not abate of its own accord. In severe cases, it can cause a colony to die. Also, contaminated combs and equipment can cause EFB to recur. The bacterium that causes EFB does not produce spores, but combs contaminated with it can still re-infect bees in subsequent years.

Question 4

EFB - Spread

Answer 4

Natural methods of spread:
o drifting, where a worker bee may go into the wrong hive, taking spores with it
o swarm from an infected hive
o robbing; probably the most important bee-based method of spread. Bees from other colonies loot the
stores of colonies weakened or killed by foulbrood, and carry spores back to their own colonies. Beekeeper methods of spread:
o moving infected combs from one colony to a healthy colony
o uniting a weak (diseased) colony with a stronger colony
feeding honey from a dubious source to bees
trapping pollen from infected colony and feeding to healthy colony
o inspecting hives on remote site with dirty gloves and suit after inspecting own infected colony hiving unknown swarms near healthy colonies
o buying old equipment without cleansing before use
moving bees to area with large numbers of colonies close by, e.g. pollinating sites purchasing infected stock of bees

Question 5

A detailed account of the development of EFB within a colony

Answer 5

There are three important facts involved in the spread of Melissococcus plutonius in a colony:
o M. plutonius never forms spores. The normal vegetative cells are infective and reproduce in huge numbers in the infected larva.
o The bacteria infects ventriculus of a larva, and so the bacteria, are “sealed in” until the larva pupates and the connection between the ventriculus and hindgut opens, when all the waste and bacteria that have been stored in the larva’s gut pass out into the cell
o Very young adults clean the cells out and later produce food that they feed to larvae.
Taken together these phenomena explain how the disease spreads through the colony. Infected larvae that survive to pupation discharge the contents of their guts into the cell. House bees pick the bacteria up when they clean the cell and subsequently feed them to the young larvae in brood food. When a larva spins an inadequate cocoon, the bacteria are more accessible to the house bees.

Question 6

Explain why the visual evidence of EFB infection is likely to vary throughout the inspection season. 6

Answer 6

1. Impossible to spot EFB when there is little brood. The house bees remove the infected larvae quickly with their package of EFB spores sealed inside, leaving just a pepperpot brood.
2. In spring, more brood than adult bees, nurse bees may only just be able to keep up with demand for brood food.
3. So only healthy larva to survive and pupate. The infected larvae die of starvation and become visible to the beekeeper.
4. When there is plenty of food for both larvae and bacteria, larvae may survive, perpetuating the disease.
5. The house bees still recognise infected larvae and remove them, leaving pepperpot brood pattern but no evidence of cause.
6. As the bees clean out the dead and dying larvae, the clinical signs of the disease disappear and the levels of bacteria are reduced.

Question 7

What are the signs of EFB 9

Answer 7

1. Best time to spot it is in spring build up (may/June)
2. Visible in larva - uncapped cells but easily confused with other brood abnormalities
3. Large larvae (3-5 days from capping) lose segmentation, contort and ‘melt’; pearly white to yellow to light brown-green
4. Dies at an unnatural attitude, twisted spirally around walls or stretched out lengthways
5. Confused with sacbrood, PMS
6. Pull white gutted larva apart - bacteria are white lumps/chains (contents shd be golden brown)
7. Death by starvation
8. Dead larva usually QUICKLY removed in one piece so hard to spot
9. Decomposes rapidly to scale, is easily removed.
10. Pepperpot - dead larva are either seen or there are just empty cells present
11. EFB LFD

Question 8

Describe the impact of EFB in colony 5

Answer 8

1. Nurse bees carry spores on mandibles from previous cleaning duties.
2. Larvae starve/survive; Survivors spread disease
3. Bacteria sealed in until pupation when hind gut connects with ventriculus and the pupa voids into cell.
4. Pupal defecations contaminates mouth parts of house bees when cell cleaning, who later contaminate brood food as nurses
5. Can fluctuate in colony as larva only die if on short rations

Question 9

Describe the lifecycle of EFB 6

Answer 9

1. The larva ingests the bacterial spores in brood food from infected nurse bees
2. Germinate in the gut and multiply between the peritrophic membrane and the larval food
3. Bacteria eats larval food in stomach and it starves to death in 4-5 days and is removed. Disease contained
4. Secondary infections can smell
5. Or the larva is fed enough and survives to defecate into the bottom of the cell after the 5th moult (disease spread)
6. The faeces will contain spores that the young house bees clean out, infecting their mandibles. Can survive 3 year in old comb.

Question 10

Demo how to hold frames with suspected EFB

Answer 10

1. Take out frames of stores to make space.
2. Clear frames of bees: Fingers on sides of frame, thumbs over top, shake hard into gap without knocking box
3. Know what looks normal and look for the unusual: poor brood pattern, gaps, abnormal larvae
4. Photograph unusuals
5. Contact SBI
6. Wash gloves
7. Impose a standstill

Question 11

What is the correct course of action if EFB is suspected and describe the possible treatments? 6

Answer 11

1. Notify the National Bee Unit and place the apiary and all equipment on a self-imposed standstill
2. Upon diagnosis, the regional bee inspector will issue a formal standstill notice, which the beekeeper signs.
3. The beekeeper then follows the inspector’s instructions implicitly.
4. Severe - inspector may order the destruction, burning and burial of the bees and combs, which he will supervise.
5. Mild - the colony may be treated with antibiotics (Oxytetracycline hydrochloride) and/or shook swarm
6. You cannot move bees until the standstill order has been revoked in writing after a second visit.

Question 12

What antibiotic, how it works, best time to administer and what else will help 6

Answer 12

1. Oxytetracycline hydrochloride
2. A bacteriostat that curtails ability of bacteria to reproduce so enabling colony’s natural disease control mechanisms to overcome disease
3. It does not cure EFB but supresses it
4. Best time to administer is when there are no symptoms ie few affected larvae - larvae that survive defecate and continue cycle
5. Combine with a shook swarm
6. Do NOT use honey for humans.

Question 13

For each treatment (destruction; antibiotics; shook swarm; SS+AB) describe the possible outcome for the colony and for other colonies in the same apiary and nearby

Answer 13

1. The disease should be contained whatever the action, and the inspector will decide which course of action is most likely to given him this outcome.
2. In the case of destruction, the bees in that colony will all die and there will be no spread of the disease providing the beekeeper has adequately scorched and disinfected all their equipment.
3. The inspector will return after 6 weeks to retest remaining colonies are free from EFB before lifting the standstill order in writing.
4. In the case of antibiotics, the least effective time to administer them is when the symptoms are showing. Oxytetracycline hydrochloride is a bacteriostat and curtails the ability of the bacteria to reproduce, enabling the colony’s natural disease control mechanisms to overcome the disease. This treatment is only effective when the level of bacterial infection is low – it is the larvae who survive that continue the cycle of infection, putting at risk all the bees in the area through drifting, robbing and swarming.
5. In the case of a shook swarm, this removes infective bacterial in the combs, but the surviving bees will still be carriers – EFB may be endemic – and may still spread the disease through drifting, robbing and swarming.
6. Antibiotic treatment + shook swarm will remove the infective bacteria from the combs and reduce the likelihood of EFB, present in the adult bees, spreading the disease through drifting, robbing and swarming.

Question 14

Describe in detail the development of European Foul Brood (EFB) in a honey bee larva,
including the mechanism of transmission from one larva to another. 10

Answer 14

Development:

• The bacterium Melissococcus plutonius is the cause of EFB.
• It never forms spores. It is infective in the vegetative state.
• The bacteria multiply in the mid-gut (ventriculus) in huge numbers and compete with the larva for its food.
• The bacteria remain in the gut and do not invade the larval tissue.
• If the larva dies, it does so because it has been starved of food.

Transmission:

• The contents of the ventriculus of a larva together with the bacteria are sealed in until the larva pupates. Then the connection between the ventriculus and the hind gut opens. Now all the waste and bacteria are free to pass into the cell.
• Young nurse bees clean out the cells. Later they will produce brood food and feed the young larvae which subsequently become infected.

Question 15

List the steps needed to perform a “Shook Swarm” for the control of EFB.

Answer 15

Go through the existing colony to find the queen and make her safe. Not essential but gives peace of mind.
• Move the existing colony to one side.
• Place a clean floor on the original site with a queen excluder on top. This will prevent the shaken colony from absconding.
• Add a new brood box with 11 new frames and foundation.
• Remove four frames from the middle leaving a gap into which to shake the bees.
• From the original brood box take each frame in turn and shake the bees into the new, clean brood box. Place the now bee-less old frames in a separate container.
• Shake any remaining bees from the brood box or brush them in carefully.
• Insert the remaining four frames. Let them find their place by gravity, do not push them down
and squash the bees.
• Introduce the queen. Add a crown board, eke and feeder. Feed 1:1 syrup.
• A week later quickly check that the queen has started to lay, remove the queen excluder and replenish the feeder. Keep feeding until most of the foundation is drawn (this will not be necessary if there is a flow on).
• It is a good idea to treat for Varroa to remove the ectoparasitic mites in the first few days.
• Dispose of the old brood best by burning. Throughly clean all the other items removed before re-use.