B451 - ACARIASIS

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B451 - ACARIASIS

Nature of the disease (see picture)
Acariasis is a disease of adult honey bees caused by the tracheal mite Acarapis woodi. The mite is an internal parasite of the respiratory system.
Classification
OIE List B disease
Susceptible species
The honey bee (Apis mellifera), the Africanised honey bee (Apis mellifera scutellata), and the eastern honey bee (Apis cerana) are the only known hosts of this pest. Drones, workers, and queens may be infected.
Distribution
Acariasis occurs in Europe, Russia and parts of Africa and Asia. It is not present in the Pacific Island countries and Territories, Australia, New Zealand or Japan.
Clinical signs
Generally only newly hatched bees less than 10 days old are susceptible. There are no reliable clinical signs. The disease spreads slowly and it may take some time to be recognised.
Mortality rate can be moderate to high. Usually only when the infestation is high is it apparent. Affected bees can’t fly but remain squatting with extended (twisted) wings
Post-mortem findings
The pathogenic effects depend on the number of mites within the trachea. As the population increases the tracheal walls appear opaque and discoloured with blotch black areas.
Differential diagnosis
 
Specimens required for diagnosis
A sample of bees (about 50) is collected at random from the suspect colony for dissection and demonstration of mites.
Transmission
Infestation spreads by direct contact between bees. The mite primarily spreads between hives by fleeing bees and drones. Over longer distances, the disease is spread by swarms from affected areas, fleeing of queens, and movements of bees and beehives from affected areas.
Risk of introduction
Acariasis is only likely to be introduced into a previously free country by deliberate or natural introduction of infected bees. Mites do not persist in bee or bee products. Mites leave the tracheae after the death of the bee. If the mite does not locate a new host within 24 hours, it will die. Drifting bees between hives and swarms from infested colonies are ways that the mite can be spread within and between apiaries.
Control / vaccines
Many chemicals have been developed and tested for the control of tracheal mites in Europe. Only menthol crystals are currently approved in the USA.
References
  • Office International des Epizooties, 2002
  • SPC, Paravet Programme, 2001