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Swans Killed by Infection (1 Viewer)
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YourBirdOasis
Well-known member
Total bummer, but the article doesn't say if anyone knows how these birds acquired necrotic enteritis? I know it's a common affliction on poultry farms and I think the bacterium that causes it occurs naturally in the environment and even at low levels in the intestines of healthy birds. Could it just have been aggravated in these wild swans because of the unusual stress of suffering any exceptionally cold period?
MJB
Well-known member
You may well be right, but another candidate is an evolved strain of necrotic enteritis from poultry. Year-round poultry breeding allows many generations in a short space of time, allowing poultry intestinal flora many more opportunities each year to evolve independently of wild-living strains that are confined to species that breed only once a year, like swans, or twice a year like many small passerines.
The supposition is that a particular evolved strain is not compatible with the standard strain of intestinal flora, effectively poisoning the recipients. However, all this has to be seen in the context that many evolved strains of necrotic enteritis probaby exist in poultry, but most if spread to wild birds won't have catastrophic effects (pehaps none at all), although if breeding performance is affected in any way, a slow decline could occur if effective defences do not evolve in response.
It's just another possibility that needs to be kept in mind in research into otherwise inexplicable population declines.
MJB
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