Hi all
I realize that there is a surfeit of information available on the subject of honey bee health and much of it is contradictory. In 2014, Wolfgang Ritter published the epic "Bee health and Veterinarians," of which I have a copy. It runs over 300 pages and covers all of the important topics.
> Maintaining bee health is a central responsibility in beekeeping, for both professional and amateur beekeepers, because only healthy bees are able to pollinate successfully and achieve a good honey harvest. Bee losses have become an increasingly serious problem throughout the world. ... This publication provides a concise but comprehensive overview of this complex set of problems.
SOURCE:
Ritter, W. (2014). Viral diseases. Bee health and veterinarians, 161-165.
http://web.oie.int/boutique/index.php?page=ficprod&id_produit=1333&lang=en
An excerpt on Nosema, which we have been discussing, contributed by Ingemar Fries:
Colony-level virulence
> Some studies suggest that N. ceranae is a colony-level virulent parasite and that, unless they are controlled infections eventually lead to colony collapse. However, most published data on colony losses linked to N. ceranae infections are correlations and fail to provide evidence of cause and effect. Fumagillin is effective in controlling N. ceranae infections, but its use is not allowed in the European Union.
> In the USA, infections of N. ceranae have been present for more than a decade and a metagenomic study failed to link colony failure in the USA to N. ceranae infections. Recent data demonstrate that infections of N. ceranae may be present in most colonies without measurable adverse effects (36). Monitoring data from both Europe and South America have failed to link N. ceranae infections to colony losses.
> Thus, it appears that the parasite is probably benign at the colony level but may cause losses if combined with yet undetermined factors. The few data yet available on colony level virulence of N. ceranae infections are obviously contradictory. The discrepancies may be due to climatic or other as yet unresolved factors. There may even be differences in virulence in different isolates of the parasite , and different variants of N. ceranae have been described.
Wolfgang Ritter authored the section on Viruses, which is lamentably brief. The Summary follows.
> Up to the present day, the pathogen changes of only a small number of the 20 different bee viruses have been identified. Many viruses cannot by themselves infect a bee: either the bee must have been previously weakened by disease or parasites are, preferably, used as carriers. Therefore, a number of viruses became important only with the spread of Varroa. In fact, these viral diseases can be only indirectly controlled through the parasites.
Therapy of viroses
> A medicamental therapy of viroses is actually impossible. Nevertheless, some molecular genetic methods such as gene silencing are in development. For all viruses transmitted by the mite Varroa destructor, however , increasing mite infestation leads not only to an enhanced number of infested bees but also to an increase in the number of deformations. This can only be prevented by controlling the Varro a infestation throughout the year. If treatment is carried out too late, most of the mites may be killed , but the virus infection of the bees persists and the colony continues to be damaged. This will typically lead, finally, to the death of the bee colony.
Ingemar Fries has been writing on Nosema since at least 1984:
Fries, I., Ekbohm, G., & Villumstad, E. (1984). Nosema apis, sampling techniques and honey yield. Journal of Apicultural Research, 23(2), 102-105.
Wolfgang Ritter has written on Varroa and its associated problems since at least 1981:
Ritter, W. (1981). Varroa disease of the honeybee Apis mellifera. Bee world, 62(4), 141-153.
PLB
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