Ingemar Fries writes:

We investigated Varroa destructor mite population
growth in a line of honey bee (Apis mellifera)
colonies that have survived mite infestation for
seven years without treatment, and in a
line of colonies that had been treated to control the mites.

The control of mites by
beekeepers removes the selective pressure on
both the host and the parasite (and viruses)
that could produce host-parasite co-evolution
with long term survival of both.

We now have independent studies
suggesting that adaptations that lead to host-parasite
co-existence can occur both in the
bee and probably also in the mite populations.

This scenario may evolve provided the beekeepers
do not interfere in the host-parasite coevolution
by controlling the mites. However, it
should be emphasised relying on a natural selection
strategy to overcome problems with V.
destructor mites is likely to cause massive bee
losses and to be totally unacceptable to apiculture,
agriculture and horticulture, not to mention
the ecological consequences with reduced
pollination.

-- 

source
Possible host-parasite adaptations in honey bees infested
by Varroa destructor mites*
Ingemar Fries, Riccardo Bommarco
Apidologie 38 (2007)

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