3.16 - Other Diseases (Nosema, Acarine and amoeba)

Question 1

Nosema Apis v Nosema Ceranae

NC more V

Answer 1

N. ceranae is a more virulent parasite than N. apis. It is more adapted to heat than N. apis; it can survive a broader temperature range: The pathology of N. apis reflects its response to temperature.

25 degrees - C infects bees more quickly
37 degrees - C survives whereas Nosema apis dies

Question 2

Malphigomoeba Facts

What is it and what does it affect?

Answer 2

Malphigamoeba Malificae = protozoan

…is a single celled parasite that affects the excretory organs of the honey bee.
The effects on the colony are unknown but is associated with dysentry, slow build up in Spring and a shortened lifespan for infected bees.

Question 4

Signs of positive identification of nosema 6

Answer 4

1. The colony fails to build up in spring
2. The are steaks of diarrhoea on frames and combs
3. Microscopic investigation (grinding the abdomens of 30 bees in 10ml of water and mounting some goo on a slide at x400 magnification) will reveal nosema spores which look like small grains of rice
4. Pulling apart a bee will reveal the ventriculus.
   
   1. A healthy bee’s looks straw brown with distinctive constrictions.
   2. Infected bee’s is white, swollen and the constrictions are obscured.
5. Faecal material examination. Collect faeces of bees on clear glass placed placed near the entrance. Scrape off the deposit and mix it with a drop of water and prepare a wet mount from the resulting suspension.
6. Do the same with the Queen by trapping her in a petri dish for about a hour. Queen faces appear as clear colouress liquid which can then be transferred to a microscope slide and covered with a cover slip.

Question 5

Describe the Nosema life cycle 6

Answer 5

1. A microsporidian ingested via infected faeces as HB clean nest as they are cleaned up.
2. Nosema infects epithelial cells of ventriculus - fires a hollow tube at target cell and microsporidian contents pass through tube into host cell.
3. Multiplies over five days until cells are packed with spores.
4. Cell ruptures, shedding spores into gut to be excreted, starting another round of infection, particularly when bees confined (eg in winter).
5. Dysentery associated with N apis and prolonged confinement leads to defecation in hive, prolonging the infection.

Question 6

What are the spread vectors for nosema 3

Answer 6

1. From infected to non-infected bees through contaminated water/food.
2. Through trophillaxis
3. Cleaning contaminated combs

Question 7

What is the impact of nosema on a bee 6

• Lifespan
• Protein digestion
• HPG
• Fat bodies
• BQCV
• Dysentry

Answer 7

1. Sickness not apparent but lifespan halved and honey production down.
2. Epithelial cell function and enzyme production disrupted/cease so cannot digest protein.
3. HPG do not develop so cannot feed brood so becomes forager earlier.
4. Winter bees cannot lay down fat bodies.
5. Queen may stop laying/die/be superseded. BQCV may result if queen larvae feed N Apis.
6. Increase of water in rectum leads to dysentery which makes N apis worse; in winter because bees void in hive

Question 8

How does summer affect nosema apis 2

Answer 8

1. Infections tend to clear up because bees void away from the colony.
2. Confinement makes it worse - eg when migrating/bad weather

Question 9

How does winter affect nosema 3

Answer 9

1. NA causes severe problems in winter: dysentery voided in hive because of cold causes more bees infected
2. Longevity of autumn bees shorter, as not enough fat bodies.
3. Even if bees survive, they do not have developed HPF to produce brood food, causing spring dwindle.

Question 10

What treatments for nosema are currently available in the UK 5

Answer 10

1. No medical treatments
2. Thymol fed in winer syrup is said to make a difference
3. Adapted Bailey frame change for a weak hive.
4. Requeen susceptible colonies with queens from more tolerant stocks.
5. Good husbandry - maintain stong, well fed colonies

Question 11

Nosema ceranae: differences with apis 7

Answer 11

1. Spores fewer and more slender than apis
2. No seasonal variation
3. No dysentery
4. Compromises immune system by providing entry point for viruses and bacteria
5. Slower build up but continual increase, regardless of season, means ultimately higher levels of infection
6. Also spread in pollen as it is moistened with nectar from bee’s crop so infects very young bees
7. Apis damaged by heat; ceranae damaged by freezing

Question 12

What would arose suspicions that a colony might be infected with Nosema.

Answer 12

Bees affected with Nosema go about their work as usual showing no signs of ill-health until shortly before death. However their lives are shortened and their brood food glands do not develop properly so they are unable to feed brood.

• The colony dwindles and fails to build up in Spring.
• Bees die in the colony (death comes suddenly) and on first inspection they may be heaps of dead bees on the hive floor plus some in front of the hive. It is likely an infected colony will be more prone to dysentry.
• Signs are therefore more clearly seen in Spring after which all signs may disappear until next Spring.

Question 13

Outline the lifecycle of Nosema indicating in your answer how it is transmitted within the colony and the effects on the individual bee and the colony.

Answer 13

1. Faeces of infected bees contain millions of spores of N apis.
2. Some are found on the comb and frames. Nurse bees clean up the mess and eat it.
3. The spores then pass into the mid-gut (ventriculus) where they germinate and infect the epithelial cells that line the mid-gut.
4. Once inside the cells the spores multiply feeding on the cell contents and finally killing the cell.
5. New spores are formed which, in ideal conditions, can happen in five days.
6. The host cell breaks down and the spores are released into the bees gut. Some of these invade new host cells, the remainder are voided into the mid-gut and the cycle starts again

The effects:

• The hypopharyngeal glands of infected bees do not develop properly so they are unable to feed brood food.

Over time the colony will dwindle and fail to build up in Spring as there will not be enough bees to feed the brood or keep it warm.

• Not being able to feed brood, infected bees become foragers earlier.
• In Spring snd Summer the life span of the bee is halved.
• Within the individual bee there are changes to the epithelial cells in the mid-gut. This impairs their normal function of producing digestive enzymes which may cease altogether.
• In winter there is less protein stored in fat bodies so winter bees do not live as long as is required to enable the colony to build up in Spring.
• Also in winter the rectal contents increase in water and may be voided in the hive and around the entrance, this is a condition known as dysentry.
• It is rare for queens to be infected but if they are, they stop laying and die.

Question 14

Describe in detail the management of a weak colony heavily infected with Nosema.

Bailey comb change for weak colony

Answer 14

The aim is to move the colony on to clean combs as soon as possible without stressing the bees.

The procedure is the Bailey Comb Change for a weak colony.

1. Remove all non brood frames from the existing brood box. Close up with dummy boards.
2. Place a queen excluder over this box with an eke with an entrance above facing the same way as the original entrance.
3. Above the eke place a clean brood box. Into this insert the frame from the bottom box that contains the queen. Add clean frames with foundation or sterilised drawn comb so the the number of frames mirrors the frames in the bottom box. Close up with dummy boards.
4. Seal the original bottom entrance.
5. Add the crown board and eke. Feed with 2:1 syrup to help the bees build comb (contact feeder preferred). Place the roof on.
6. A week later: Move the old frame minus the queen to the bottom box.
7. Add two or three more sterilised drawn combs (or foundation) in top box. Top up feeder.
8. Week 4 or 5: Place upper box on a clean floor and create bottom entrance.
9. Add additional drawn comb until the correct number is reached.
10. Destroy all the old frames. Sterilise the old brood box, queen excluder, floor etc

Question 15

Removal of nosema spores: Explain how to fumigate comb using ethanoic (acetic) acid.

Answer 15

Start with a solid floor (not concrete) or board and place the Brood Box/Super + comb to betreated on top.
• Place an absorbent pad on top and soak with 80%. Acetic Acid (amounts vary from 100 to140ml). The pad should have a piece of plastic underneath to prevent the acid coming into direct contact with the frames.
• Repeat with additional boxes and pads as required. Cover the top with a crown board and roof.
• Floor entrance needs to be sealed.
• All gaps and joins should be sealed with packing tape or similar. Ideally seal the whole stack
with plastic sheeting or a large plastic sack to minimise escape of the fumes.
• Fumigate for at least a week and then ventilate for a further week before use.

Question 16

Acetic Acid: What safety precautions should be taken?

Answer 16

• Wear gloves, eye protection, breathing mask and overalls as the acid will burn skin, ruin clothing and cause internal bleeding if inhaled.
• Do not place the stack on concrete.
• Remove castellated space bars from supers and clean metal runners before smearing with petroleum jelly (Vaseline) as the acid will corrode metal. Little can be done to protect wire in foundation/comb.

Question 17

What constitutes a suitable sample of bees to test for the presence of Nosema and why? 4

Answer 17

28 bees are needed to give a 95% chance of finding an infection affecting 10% of the bees or a 99% chance of an infection affecting 15% of the bees.

• 30 bees collected in a matchbox or similar give a good indication of a comparatively low level of infection.

Question 18

List the steps of a laboratory method to confirm the presence of Nosema in a sample of bees. 9

Answer 18

Remove the abdomens from the bees and place in a mortar, add 10ml of water and crush with a pestle.

• Place a drop of the resultant solution on a slide and add a cover slip.
• Place under a microscope at x400.
• The spores, if there are any, look like tiny grains of rice. The more there are, the greater the infection.

Question 19

Why is regular brood comb change important?

Answer 19

The bees build worker cells that are 5.2-5.5mm diameter; 6.2mm for drone brood. Each time a larva pupates it weaves a cocoon so that over time the cell gets smaller which, will affect the next generation of larvae.

• Further, the cocoon will contain the dross and faeces from the time the larva voided its gut at the fifth moult. This will contain any pathogenic material that might have been affecting the larva or pupa.
• Each time a bee emerges, nurse bees enter the cell, remove any dross and polish the cell ready for the queen to re-lay. In doing so they will pick up and pass on any disease from that cell.
• The recommendation is that all brood comb should be changed every two years even if it has been fumigated when not in use.

Question 20

Briefly describe a method of changing all the comb in a strong colony with two supers, during a nectar flow in May? (Shook swarm)

Answer 20

• Prepare a clean brood chamber filled with new frames of foundation or sterilised drawn comb, a clean floor, crown board and queen excluder.
• Move the existing hive to one side and place the new floor on the original site. Place the queen excluder over the floor and the new box with frames of foundation on top of the queen excluder.
• Remove the centre four frames and place them to one side.
• Examine the old brood chamber, find the queen and place her in a queen cage.
• Place the queen in her cage between frames of foundation in the new box so that she can be released in the new box when shaking the bees is complete (or just somewhere safe).
• Shake all the bees from the old chamber. Grip each frame in turn and with one third overlapping into the gap in the new chamber give a sharp downward shake with a sudden stop. Avoid jarring the comb against the chamber. The bees will fall off into the chamber. Any left on the comb can be brushed off. Place the now empty comb into a separate container.
• Shake and brush all the bees from the old equipment into the new chamber.
• When all the bees are in the chamber, gently place all the spare frames into the box. Let them find their position through gravity.
• Put the crown board in place.
• Depending on the strength of the flow you may or may not need to feed. It is best to delay feeding for a couple of days to allow any contaminated nectar carried by the bees to be used for comb building. Feed with heavy syrup (1kg white granulated sugar to 600ml water). Contact feeder is best.
• After about a week check that the queen has started to lay. If so remove the queen excluder and sterilise it.
• You may need to continue feeding until all the combs are drawn.
• The old comb can be rendered down in a solar extractor and the frames sterilised but if EFB has been present then frames and comb should be destroyed. You might wish to destroy them in any case.
• As for the supers. The aim of this process is to move the colony onto clean comb. Any honey can be extracted but then it is best to treat the frames and comb as above, rendering and sterilising or destroying.

Question 21

Amoeba - cause and signs

Answer 21

Amoeba is caused by a protozoan amoeba-like parasite

Malpighamoeba mellificae.

Cysts are ingested with food and germinate in the gut.

They migrate to the Malpighian tubules (the ‘kidneys’) to create more cysts that then accumulate in the rectum and are excreted.

The infection seems to have no effect on the colony; there are no specific symptoms and no treatment.

Often seen under a microscope when examining a sample for Nosema - grainy circular cysts, larger than the rice-shaped Nosema spores.

Acetic acid destroys the spores.

Question 22

Symptoms of Acarapisosis

DUG

Answer 22

• Bees clustering in front of hive, confused and diorientated
• Bees unable to return to the colony
• Bees crawling up stems of grass in front of hive

Question 23

Acaraposis Woodi - (parasitic tracheal mite) Facts

Answer 23

• Size: Female is 100µm wide and 175 µm long depending on whether you include the hairy bits or not. Males slightly smaller
• Lives in trachea
• Feeds by piercing the cuticle inside trachea and sucking haemolymph
• each female lays between 5-7 eggs
• adult females develop about 14 days after eggs are laid, males a few days earlier
• Leaves trachea and crawls up a hair hanging on by hind legs
• waits for suitable host (less than 9 day old bee) and grabs hairs before climbing down to first thoracic spiracle (drawn there by wings and puffs of air)

Question 24

Acarine Diagnosis

Answer 24

Sample of 30 bees

choose bees crawling around at front of hive, unable to fly or bees from outside frames (older ones not younger nurse bees)

If live bees, freeze for 24 hours

Impale each bee using a double needle placed at an angle away from the head through the thorax between the second and third pairs of legs. The bee should be ventral side up on an angled cork base.

Using a single edged razor blade, cut the head and first pair of legs off; make the cut from behind the first pair of legs to the back of the bee’s head. Remove the severed head and front pair of legs with tweezers.

Use fine-tipped tweezers to peel the collar away and expose the tracheae more fully.

Pull upwards with a circular motion, following the ring of the collar. It will peel off easily, usually in one piece.

In a healthy or uninfected bee the tracheae have a uniform, creamy-white appearance. In infested bees the tracheae show patchy discolouration or dark staining, (melanisation, caused by mites feeding). In addition the eggs, nymphs and adult stages of the mite may also be seen in the trachea.

As mites enter through the spiracle, check the outer end of the trachea first. Light infestations may be difficult to see, heavy infestations are easily visible as shadows or lumpy dark objects in tracheae that can be clear to dark brown. Old and/or heavy infestations will render the trachea orange, brown or black.