Bees always carry a range of bacteria, viruses and a range of other microorganisms. The same applies to the mites.
A wide range of bacteria is found on bees. These include lactobacilli and bifidobacteria and all kinds of species which can also cause disease in humans. Some data is also available about seasonal changes in the bacterial composition. It is known, for example, that certain species in the winter period can reach a share of 30%, while in during the year they are hardly present. Which bacteria are present on mites is less well documented.
The viruses present in bees are common insect viruses. The approximately 20 well-known bee viruses are almost always present. DWV (Deformed Wing Virus) and the ABPV complex (Acute Bee Paralysis Virus) are considered to be the primary viruses in bees. Viruses always occur concurrently with other viruses; many viruses are very similar. The quantities of each of these viruses vary, even during the season. It is unclear to what extent viruses affect each other. The part of the bee in which viruses are present, has been partially mapped out. Some viruses occur only in the intestine, or in the salivary glands or mouth parts, other viruses occur mainly in the fat body. The place where the Varroa mite infects the bees with viruses (between the 2nd and 3rd segment) is located near the supply for the flight system. This means that viruses attack internally first. The symptoms are not always immediately visible. A number of viruses have been found in both the bee system and the Varroa system. It has also been demonstrated that certain viruses are transmitted by Varroa.
What do bacteria mean to the Varroa mite?
For a long period, the Varroa mite in itself did not cause insurmountable problems. In principle, a bee colony can live with the Varroa mite. Over time, one or more factors have come to play an additional role. For about 10 years now, the scientific world has placed the blame on the viruses.
In our model of microbial competition the presumption is that the Varroa, together with the bacteria, form the problem. The role of viruses here is considered as complementary and supportive. The significance of the bacteria for the mite is perhaps stated somewhere, but anno 2012 in the scientific world, this does not belong to the assumptions (hypotheses) or insights.