B455 - VARROASIS

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B455 - VARROASIS

Nature of the disease
Varroa mite (Varroa jacobsoni) is a large parasitic mite of honey bees. It feeds on the haemolymph of honeybee brood and adult bees.
Classification
OIE List B disease
Susceptible species
Varroa is a parasite of all races of the European honey bee.
Distribution
Varroa is widely distributed around the world. Within the Pacific region, the parasite is present in Papua New Guinea. It has been found in Asian bees in the Torres Strait islands, but not on mainland Australia.
Clinical signs 

Numerous, newly emerged adult bees at the hive entrance with deformed wings legs and abdomens. Patchy brood patterns may be evident in advanced infestations.
Mites can be found inside sealed brood cells.

 

Post-mortem findings
 
Differential diagnosis
 
Specimens required for diagnosis
Pupae are removed with a hive tool or forceps and examined externally for reddish-coloured mites. A minimum of 100 pupae should be checked. Mites should be collected for laboratory examination.
Transmission
Varroa will spread between colonies and apiaries when hive components containing infested brood or adult bees are interchanged during normal management practices.

Movement of hives and queen bees by beekeepers is a very effective means of spreading the disease.
There may also be transfer of mites to and from bees visiting the same flower.

Risk of introduction
Importation of contaminated bee keeping equipment or infested queen bees or brood combs could be associated with introduction of the disease.
Control / vaccines
Varroasis is an OIE List B disease and the preferred option should be to eradicate this disease if introduced. This would involve:
  • Isolating infested apiaries
  • Destroying affected bees, comb and hive components
  • Locating and destroying feral bee nests in the vicinity

If the disease becomes widely established, acaricides (e.g. dicofol, amitraz, phenothiazine, Folbex-R, or even tobacco smoke) can be used to control the varroa mite. These can be applied in the form of dust, smoke, aerosol, spray or as an evaporative or systemic agent. However treatment tends to be expensive and the risk of residues in honey needs to be managed.

References
  • Office International des Epizooties, 2002
  • ROOT AI (1990), Varroa mites In ABC and XYZ of Bee Culture, ed Root Company, p 319-325