Honey Bee Diseases Foulbrood - Identification and Management

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Honey Bee Diseases Foulbrood - Identification
and Management
Rick Fell, Virginia Tech
Nosema
American Foulbrood
Chalkbrood
European Foulbrood
Sacbrood
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Major Diseases Affecting Honey Bees
1. American foulbrood - bacterial 2. European
foulbrood - bacterial 3. Sacbrood - viral 4.
Chalkbrood - fungal 5. Nosema - fungal
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American Foulbrood
Bacterial disease of honey bee larvae
Causative organism Paenibacillus larvae
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American Foulbrood

• Infective stage is the spore, enters body by
  ingestion of contaminated food
• Attacks young larva (lt2 days of age), kills in
  late larval to pupal stage

• Spores germinate about one day after ingestion,
  multiply in midgut, penetrate into body cavity,
  larva dies from a septicemic condition

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American Foulbrood

• Larvae/pupae decay in cells, change color (tan to
  dark brown) and become ropey pupae show tongue
• Form scales in cells that are difficult to remove

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American Foulbrood - Recognition in the Bee Yard
1. Critical to recognize at an early stage of
infection 2. Must be able to distinguish from
other diseases 3. Scan frames for perforated
cappings when inspecting 4. Open cells and
examine larvae
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American Foulbrood - Recognition in the Bee Yard

• Larval characteristics
• Color - tan to dark brown
• Position - bottom wall of cell, flattened
• Consistency - ropey
• Pupal characteristics
• Tongue visible, color and position same as larva
• Scale
• Adheres tightly to lower wall

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American Foulbrood Infection

• If you suspect your colony may have AFB

1. Contact bee inspector
2. Confirm diagnosis before attempting treatment

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American Foulbrood Identification

• Positive identification of AFB can be made with
  the Vita Diagnostic kit
• Determination is based on AFB specific antibodies
• Disease confirmation can also be obtained by
  sending a sample to the USDA Bee Research
  Laboratory at Beltsville MD where they maintain a
  disease diagnostic service.
• Lab diagnosis

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American Foulbrood - Prevention and Treatment
1. Keep AFB resistant bees 2. Shake bees and
re-establish in a new colony with frames of
foundation. Treat with an antibiotic. 3. Treat
colony with an antibiotic 4. Kill colony and
destroy equipment by burning
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Hygienic Bees Resistance to AFB

• Hygienic Bees
• New World Carniolan (Sue Cobey, Ohio State Univ)
• Selected for rapid buildup, overwintering,
  tracheal mite resistance, gentleness,
  productivity, hygienic behavior
• Minnesota Hygienic Bees - M. Spivak
• Selected for disease and mite resistance. Good
  AFB resistance.

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Hygienic Behavior

• Natural defense mechanism against diseases and
  parasites
• Hygienic bees detect, uncap, and remove diseased
  brood from combs before the disease becomes
  infectious
• The hygienic trait can be found in approximately
  10 of managed colonies

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Testing for Hygienic Behavior in Bees
Technique uses liquid nitrogen to kill
brood Frames are placed in a hive and checked
after 48 hours. Amount of dead brood removed
indicates hygienic behavior.
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Testing for Hygienic Behavior in Bees
Non-hygienic bees
Hygienic bees
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Hygienic Bees Resistance to AFB

• Minnesota bees show good resistance to AFB
• Tests with 18 hygienic colonies and 18
  non-hygienic
• 7 hygienic colonies developed symptoms of AFB (5
  recovered)
• All 18 non-hygienic colonies developed AFB (1
  recovered)

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Shaking Honey Bee Colonies for AFB Control

• Shaking bees from an infected hive into a new
  hive with foundation does not eliminate AFB
  spores
• However, spore loads are minimized so that the
  disease is under control
• Spore levels will probably increase over a
  several month period - but colonies may remain
  free of the disease
• Antibiotic treatment after shaking will reduce
  likelihood of a second disease outbreak

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Shaking a Colony for AFB Control

• Prepare new colony with frames of foundation
• Find and cage queen in AFB infected hive
• Caging the queen insures bees stay in new hive
  and slows initiation of brood rearing

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Shaking a Colony for AFB Control

• Shake bees into (or in front of) the clean hive,
  add caged queen
• Remove and burn infected frames, char hive bodies

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Shaking a Colony for AFB Control

• Add feeder pail with 11 sugar solution
• Treat colony with antibiotic (terramycin or
  tylosin)
• Free queen after several days

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Antibiotics for AFB Control
Standard treatment used as a preventative
terramycin Problem of AFB resistance to
terramycin. How widespread in VA?
New antibiotics Tylosin tartrate
Registration Approved November 16, 2005
Recommended for use in control of AFB.
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Using Antibiotics for AFB Control
Tylosin (marketed as Tylan) Manufactured by
Elanco Animal Health
Dosage 200 mg in 20 g confectioners
sugar Treatment 3X at one week
intervals Effectiveness Good results on low
level infections. Found AFB in colonies with
high infection rates after several weeks.
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American Foulbrood - Treatment of Infected
Colonies
1. Kill colony and destroy equipment by
burning 2. Scorch out hive bodies, cover, bottom
board 3. Standard treatment for many years -
effective and kept AFB levels to lt 2
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European Foulbrood
Bacterial stress disease of honey bee larvae
Causative organism Melissococcus pluton
Conditions which aggravate problems with this
disease include, cool temperatures, moisture,
food shortages. Disease affects colony build-up,
productivity, survival.
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European Foulbrood

• Non spore forming bacteria
• Infects only young larvae after ingestion kills
  larvae in the coiled stage
• Larvae turn yellowish, then brown, with white
  cross-pattern (from trachea)

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European Foulbrood

• Older larvae typically twist in cell and do not
  settle in cell bottom like AFB killed larvae.
• Larvae do not become ropey more watery or pasty.
• Scale is rubbery and easily detached

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EFB Disease Management

• Eliminate stress conditions
• good apiary sites, strong colonies
• Selection of stock (requeening)
• resistance to EFB, chalkbrood
• Treatment with antibiotics
• Terramycin for EFB

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Maintaining Healthy Colonies

• Keep resistant stock and requeen regularly
• Choose apiary sites to reduce environmental
  stress
• Make it a habit to check for diseases when
  inspecting hives (be able to recognize diseases)
• Be careful moving frames between hives, combining
  hives, reusing equipment
• Practice comb replacement
• Reduce drift between hives and prevent robbing

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Sacbrood
Viral disease of honey bee larvae
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Sacbrood

• common virus, isolated from both healthy larvae
  and adults
• older larvae may be more susceptible, die after
  the cells are sealed
• larvae killed by the sacbrood virus turn
  yellow-gray then blackish, head changes to black
  color first

Larva recently killed by sacbrood virus
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Sacbrood

• larval skin remains intact, larva can be
  removed from cell as a fluid-filled sac. Forms a
  scale, but easily removed.

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Distinguishing AFB from Other Bee Diseases
Virus infected larva of PMS, larvae die in late
larval or prepupal stage, cells may be capped
with perforation, dull white color, may have
grayish or brownish spots, not ropey
Sacbrood die in late larval stage after cells
are capped, cappings perforated. Larvae die with
head in raised position, turn yellow-gray and
then black, head turns black first.
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Sacbrood - Treatment

• No effective treatment, other than improving
  colony conditions. Reduce stress on the colony.

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Stress Diseases of Honey Bees
European foulbrood Sacbrood (Chalkbrood) Nosema
Stress conditions which aggravate problems with
these diseases include, cool temperatures,
moisture, food shortages