I just read Mr. Borst's post about collony collapse & virus control
review through articles extracts. Thinking about this topic, I
remembered I read something about mathematical modelisation of varroa &
viruses in hives some years ago (I'm the kind that like maths, equations
and models). My memories pointed me to Mussen's newsletters. I found the
article back in his sept. 2004 newsletter.
"
Mathematicians Predict Colony Collapse
It is always interesting to see how experts outside the usual realm of
apiculture can apply their expertise to beekeeping topics. In this case,
a group of mathematicians built a model to determine what number of
varroa mites (vectors) would be needed to cause a virus epidemic in a
honey bee colony. [...] The mathematical model was pretty complex, since
a whole lot of factors are involved in the process – aspects of the life
cycle of bees, life cycle of mites, virulence of the chosen virus, etc.
Their general conclusions were: The more virulent the virus (the quicker
the infected bee died), the more mites were needed to get an epidemic
started. Acute paralysis virus (APV) and Kashmir bee virus (KBV) re
virulent types. A less virulent virus, like deformed wing virus (DWV),
allows the bees to live a longer time, thus giving many bees and mites a
chance to become infected. So, their predicted numbers of mites to cause
serious problems in the summer are 12,289 for the virulent viruses and
2,315 for the less virulent ones. In the fall the numbers of mites
needed to cause trouble are reduced, as are the bee and brood numbers.
Then, the numbers are 6,830 for virulent viruses and 737 for less
virulent ones. Can our colonies reach these levels of mite loads? It is
quite likely. The literature has many articles describing counts above
those levels. Also, the mathematicians' model suggested that the only
modifications to the model that impacted the epidemic potential were
changes that reduced mite numbers. Decreasing numbers of infected bees
(resistance or tolerance) or removal of dead or infected brood (hygienic
behavior) were not effective, unless the mites were removed as the brood
was being removed. This suggests that we should place the greatest
emphasis of our studies on how to reduce the number of mites in a
colony. This information sounds similar to malaria, where if there are
no mosquitoes (vectors) around, there isn't much of a disease problem.
The complete citation for this article is: Sumpter, D.J.T. and S.J.
Martin. 2004. The dynamics of virus epidemics in Varroa-infested
honey bee colonies. Journal of Animal Ecology 73: 51-63.
Hervé
Laval, Qc, Canada
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Hervé
www.emelys.com
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