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Sacbrood

Brood affected by Sacbrood virusCausative Agent:

Sacbrood virus

General Appearance of Brood Combs:

Brood combs show some degree of irregularity in their pattern, as with AFB and EFB. Dead brood will be found scattered among healthy brood and the cappings may be discoloured, sunken, perforated or removed by the bees. Larvae almost always die after the cell has been capped.

Age of Brood Affected:

Sealed brood of seven to ten days and pupae.

Kind of Brood Affected:

Usually worker larvae only, though sometimes drones may also become affected.

Method of Disease Infection:

Nurse bees transmit the virus when they feed larvae with brood food from their hypopharyngeal glands.

The virus may survive up to four weeks in larval remains or in honey or pollen.

Cell Position of Diseased Brood:

The larva lies fully extended on the bottom of the cell with its head characteristically raised in a "gondola or banana" shape towards the top of the cell.

Colour of Diseased Brood:

The pearly white colour of healthy larva first changes to a yellowish colour, then grey, then brown and finally from dark brown to mostly black.

Characteristic field symptoms of this disease include:

* Darkening begins at the head - later spreading to the rest of the body.
* The skin of the dead larva changes into a tough plastic-like sac. Between the skin and larval body a greyish granular fluid accumulates.
* Body segmentation is maintained in the dead larva.

Ropiness of Moist Material:

Nil.

Scale Characteristics:

The scale, characteristically brittle, retains the upturned gondola shape of the body. It is located on the lower wall of the cell and can be easily removed without damaging the cell wall. This is a characteristic field symptom of this disease.

Brood Odour:

Usually odourless, though in advanced stages an occasional putrid smell may be detected.

Treatment:

The incidence of sacbrood in most colonies is low because adult bees normally detect and quickly remove infected larvae. However management practices that can help alleviate the symptoms of sacbrood can include:

* Re-queening with a young vigorous queen.
* Strengthening any weakened hives by uniting with a disease free nucleus hive of young bees.
* Move bees to better conditions with a good honey flow.
* Feed bees a sugar solution and quality pollen if supplies are low.
* Pack the bees down into fewer boxes.
* Routine comb replacement.

What Should be Sent for Diagnosis:

Comb containing suspect brood.

If comb is being sent please ensure that it is in within a waterproof container (eg jar).