At this stage it is unknown how the mite arrived in New Zealand. The evidence suggests it may have been present and undetected for up to five years. Spread is commonly by live bees, and there have been no live bee imports permitted into New Zealand for at least 40 years to protect our bee health status. The mite spreads by natural means very slowly, at a rate of 5 km a year. When first affected, hives have low numbers of mites that are not easily seen.
Numbers build up over several years until the hive dies.
It can be seen with the naked eye if bees are examined carefully. It is also visible on honeybee pupae, and appears as a dark reddish-brown dot. It is most commonly found on drone pupae. The mite does not affect humans, and has no known host other than the honeybee. The mite originated in eastern Asia and spread into Europe via Russia.