>Another is the increase in [Chronic] Bee Paralysis virus. I have seen that
In my yard, in 2014, I had 1 hive out of 5 with symptoms. The hive recovered before winter (I like to believe that it was because of my 'trick' with a separator board that separated the more infected older bees from the less infected younger bees). However, in 2015, this hive, although strong after winter, showed again symptoms of disease (already in the beginning of April), and not much later there were also symptoms in 2 more hives (so now 3 out of 6 hives). In each affected hive, both forms were present (fewer hairless black bees and many 'normal' looking paralysed or trembling bees). K-wings were also frequent. One hive recovered early summer and 2 others dwindled until I combined them and relocated the hive in another yard at the end of August (the separator trick did not work last year). The combined diseased hive has now come out of winter as one of my stronger hives. At the moment, I do not see diseased bees in front of the hive (yet).
The virus can be present in the hive at low levels without symptoms, but what causes it to multiply is not clear ("At present, little is known of how viruses establish inapparent infections in their hosts, how they become activated, in which form
and where they persist, or of interactions between multiple inapparent viruses. Ribière et al, 2010"). Literature mentions that periods of confinement and crowding are risk factors (It may be that the hive in 2014 got sick after a visit to an oilseed rape field, there were >30 colonies at a field of 11 ha). Perhaps a more virulent strain is present now, or the immunity of our bees is not sufficient to eliminate the virus.
I have heard of other beekeepers in Belgium with CBPV symptoms (in their hives) last year also, but I do not have data on prevalence of the disease.
I have the impression that it starts with a few hairless blacks and this may or may not evolve into the other form (many sick, trembling bees, this may be 50-200 bees/day in front of the hive), which is much more important for the functioning of the hive and causes it to dwindle. The dwindling phase can last for months (in my cases), so a bit of tender loving care may be necessary, I guess, if you want to help them trough. Separation of the diseased hives is probably a good idea, because a lot of diseased bees are present just outside the hive and probably on the flowers in the neighbourhood also. I did this only at the end of last season and two hives next to the diseased ones (1 m in between) did not get sick (yet), so I'm not sure how important this is.
Its seems that the hives recover on their own (in summer or fall), but the virus will probably still be present as an inapparent infection in these (and many other) hives. I think there is not much you can do about it than look at it and feed them if necessary..
Best regards,
Kris
Belgium
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