Published Date: 2011-08-30 06:07:56
Subject: PRO/AH> White nose syndrome, bats - North America (05)
Archive Number: 20110830.2659
WHITE NOSE SYNDROME, BATS - NORTH AMERICA (05)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: 28 Aug 2011
From: Merritt Clifton <email@example.com>
If a treatment is discovered, the method of mass application may
furnish a clue to eradicating bat rabies, the key to eradicating
rabies altogether. Meanwhile, what we are seeing occurring among bats
afflicted by white nose syndrome is not extinction, but evolution.
We know that European bats have been exposed to _Geomyces destructans_
because they evolved genetic resistance to it.
We know that some American bats share that resistance, albeit perhaps
as a recessive trait, because while most bats who are infected by
_Geomyces destructans_ die from it, a very few are surviving here and
By the look of it, North American bats have not had to cope with
_Geomyces destructans_ for a very long time, if ever, so there has
been no natural selection for resistance to it. Under that
circumstance, the resistance that the common ancestors of European and
North American bats must have shared has almost entirely disappeared.
Now, however, there is intensive natural selection for resistance.
Under normal circumstances, a small population of animals or plants
with a particular trait would not be able to spread the trait far and
fast, no matter how advantageous, because there would be many other
members of the species with different traits competing for the mating
opportunities and the wherewithal to raise young successfully.
Under the present circumstance, though, only the bats with the
resistant trait are able to reproduce successfully at all, and the
depletion of the bat population while habitat remains plentiful,
including food and cover, ensures that the bats with the resistant
trait will be able to rapidly repopulate and reclaim the habitat.
First, of course, enough bats with the resistant trait must find each
other to begin the process of passing it along. This may take a few
years, and there is always the risk that, meanwhile, some other
species will claim the temporarily vacated habitat.
There are, however, many other examples of disease drastically
knocking down populations of animals and plants until a resistant
strain emerges, enabling the species to rapidly recover.
Meanwhile, the depletion of the species caused by the disease is also
part of the cure, because as the susceptible part of the population
dies out, the disease has fewer and fewer potential hosts in which to
Editor, Animal People
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