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Disease Survey on Norfolk Island

24 August 2022

You may be aware that Australia carries out surveys of honey bees on Norfolk Island to determine the disease status of the honey bees there. During a recent survey a […]


You may be aware that Australia carries out surveys of honey bees on Norfolk Island to determine the disease status of the honey bees there.

During a recent survey a PCR test, developed by New Zealand, was used to look at the presence or absence of the internal mite, Acarapis woodi.  Using a PCR test means that it saves the labour of using previous methods where the tracheas of the bees have to be either manually removed or potassium hydroxide is used to dissolve body tissue leaving only the tracheas.

The first results using the PCR came up as positive.  Of course this rang alarm bells.  It was decided to check the actual tracheas of bees by using the old method of dissecting the tracheas out and examining them under a microscope.  When this as done no internal mites were found.  So it was reasoned that the original positive was a false positive.

How was this possible?  There are two (2) other external mites that are present on honey bees in Australia.  There is no evidence that they have any detrimental effect on honey bees.  They are A. dorsalis and A. externus.  See https://www.dpi.nsw.gov.au/animals-and-livestock/bees/pests-diseases/other-pests-and-diseases/tracheal-mite   So the PCR would be reacting to the presence of these external mites as they are from the same genus i.e. Acarapis.  As queen bees have been sent to Norfolk Island from mainland Australia many years ago it is reasonable to expect that these external mites would be present on Norfolk Island.

When I worked for the Queensland Department of Primary Industries in the 1980’s one of my jobs was to collect honey bee samples from the various queen bee breeders to examine them for diseases and pests so interstate health certificates could be signed for queen bees.  When examining these honey bees it was quite common for me to find dorsalis on the worker bees.  Identification was confirmed by an entomologist.

So this note is being circulated so that if you hear a story about internal mites being present in honey bees on Norfolk Island you know that it was a false positive and subsequent examination has not found any internal mites.