Hi Andrew,
The question I would be posing in the light of your query is how recently
evolved are the current molecular structures of the neurotoxins of the
Clostridium botulinum? Perhaps Clostridium botulinum is a recently evolved
bacterium (in the evolutionary history of waterfowl) and/or its neurotoxins
are recently evolved proteins. If so, perhaps there has not been enough time
for ducks and swans to evolve a mechanism of resistance to the neurotoxins.
Stephen Ambrose
Ryde NSW
-----Original Message-----
From:
On Behalf Of Andrew Hobbs
Sent: Wednesday, 8 February 2012 6:28 PM
Cc:
Subject: Botulism poisoning in waterfowl
On 8/02/2012 1:39 PM, Carl Clifford wrote:
> Andrew,
>
> The problem with Botulism is, that the cause of death is not from
> infection by Clostridium botulinum, but from neurotoxins produced by
> the bacteria. The botulinum toxins have LD50s of less than 100
> nanograms per Kg. Hydrogen Cyanide has an LD50 of only 1-3g/Kg
>
> In Thomas, Hunter and Atkinson's "Infectious Diseases of Wild Birds",
> P. 405, they state that natural immunity does not play a significant
> role in Botulism, because "The toxin is so poisonous that the amount
> required to immunise an animal is much higher than the lethal dose."
> They do say that it has been observed that naturally occurring
> antibodies to several botulinum neurotoxins were found in several
> carrion eating species of birds.
>
I wasn't actually thinking of acquired immunity. I was thinking more of
evolved immunity. Botulinum toxin (a group of 7 or 8 individual toxins
from /Clostridium botulinum and other related species./) and Tetanus
toxin (from /Clostridium tetani //) /are all proteins, and target
membrane proteins in their action. So mutants resistant to the toxins
should be possible. Indeed while humans, mice etc are very sensitive to
tetanus toxins, dogs, rats, some birds, snakes and amphibians are much
less sensitive and turtles apparently are insensitive to the toxin. Also
there is a range of sensitivities to botulinum toxins in humans with
some humans being insensitive (Schiavo et al Physiol RevJanuary 2000
vol. 80 no. 2 717-766 ). So it should be eminently feasible for ducks
and swans to have evolved immunity or insensitivity to the toxins too.
I suspect that such ducks and swans have been ferreting around in the
ooze for a long time so the question is still, why are they affected,
and has it changed recently. (however you define recently).
Cheers
Andrew
///
/
> Cheers,
>
> Carl Clifford
>
>
> On 08/02/2012, at 3:56 PM, Andrew Hobbs wrote:
>
> Hmm,
>
> Feretting around in the mud is an almost full time occupation for some
> ducks and swans so the question that comes to mind is 'why do ducks
> and swans suffer from botulism'. I would have thought that it would
> have been a sufficiently strong selection pressure to either develop a
> different food source, develop an immunity or perhaps botulism is only
> a very recent phenomenon in such conditions.
>
> Any ideas?
>
> Cheers
>
> Andrew
>
> On 8/02/2012 12:24 PM, Peter Shute wrote:
>> Is it possible that the grebes are being poisoned too, but aren't
>> dying in such visible places?
>>
>> Peter Shute
>>
>>> -----Original Message-----
>>> From:
>>> On Behalf Of
>>> Carl Clifford
>>> Sent: Wednesday, 8 February 2012 1:52 PM
>>> To: Chris Watson
>>> Cc:
>>> Subject: Re: [Birding-Aus] Botulism poisoning in waterfowl
>>>
>>> Chris,
>>>
>>> Though Grebes are divers, they feed on crustaceans, fish etc
>>> and tend
>>> not to go poking around in the mud at the bottom of the
>>> ponds. Diving
>>> ducks tend to ferret around in the bottom mud and would be
>>> more likely
>>> to get into the anaerobic layers.
>>>
>>> Cheers,
>>>
>>> Carl Clifford
>>>
>>>
>>> On 08/02/2012, at 1:28 PM, Chris Watson wrote:
>>>
>>> G'day all,
>>>
>>> A bit of a technical question. I've been monitoring the
>>> mortality rate
>>> of a few species at Alice Springs Sewage Ponds after a spike in
>>> botulism poisoning last year.
>>>
>>> I'm not a biologist, but what I've learnt is that "c" type
>>> Clostridium
>>> botulinum bacteria reside and breed in anaerobic muds at the
>>> bottom of
>>> the ponds. When we get the warmer weather the amount of bacteria
>>> increases and bottom feeding birds (swans, diving ducks) can stir it
>>> up and ingest it, resulting in the increased mortality that
>>> we witness.
>>>
>>> At the moment we are seeing a greater number of dead and moribund
>>> birds around the ponds (mostly Black Swan, Hardhead, and the
>>> occasional Grey Teal).
>>>
>>> My question is this; why are the aforementioned species affected but
>>> the grebes (Australasian and Hoary-headed) which are accomplished
>>> divers have not been observed to be affected to this point. In 18
>>> months, I have not found a single grebe carcass or seen any grebes
>>> that seem effected by botulinum toxicity. I am at the ponds at least
>>> twice a week so have a very good idea of the changes in populations
>>> and movements there. We have a fairly stable population of
>>> between 80
>>> and 120 grebes, and I'm surprised that they never seem to be
>>> affected
>>> by this toxin which always seems to take out quite a few swans and
>>> ducks (and the odd stilt and lapwing) each summer. I can only
>>> imagine
>>> that there is some difference in their feeding technique or the
>>> physiology of their digestive tract which keeps them safe from it.
>>>
>>> Can anyone enlighten me?
>>>
>>> Cheers,
>>>
>>> Chris Watson
>>> Alice Springs
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