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Published Date: 2011-09-14 10:14:38
Subject: PRO/AH/EDR> Botulism, avian - USA: (CO)
Archive Number: 20110914.2797

BOTULISM, AVIAN - USA: (COLORADO)
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International Society for Infectious Diseases
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Date: Fri 9 Sep 2011
Source: The Denver Post [edited]
http://www.denverpost.com/breakingnews/ci_18862094

Dozens of dead ducks found in Aurora park
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The city's parks department has been removing dozens of mallard duck
carcasses from Utah Park in recent weeks.

About 40 dead ducks were removed from some ponds at the park in mid to
late August [2011], said Sherri-Jo Stowell, spokeswoman for the city's
parks, recreation and open space department. Wildlife officials say
the feathered creatures died from an outbreak of avian botulism, which
typically peaks during the hotter months.

Many of the ducks appear to be infected by an avian botulism toxin,
which is often released from sediment during hot weather. Insects
absorb the toxin and infect the birds that eat them.

Denver and other areas have experienced similar outbreaks in recent
weeks as well.

Though the toxin is particularly dangerous to wild birds, cattle,
horses, and poultry, it is considered a low-risk toxin for humans,
dogs, and cats.

Officials are urging residents to avoid feeding ducks and geese
because it can reduce water quality and further increase the chances
for more avian botulism outbreaks.

[Byline: Joey Kirchmer]

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[Avian botulism is a paralytic disease caused by ingestion of a toxin
produced by the bacteria _Clostridium botulinum_. These bacteria are
widespread in soil and require warm temperatures, a protein source,
and an anaerobic (no oxygen) environment in order to become active and
produce toxin. Decomposing vegetation and invertebrates combined with
warm temperatures can provide ideal conditions for the botulism
bacteria to activate and produce toxin. There are several types of
toxin produced by strains of these bacteria; birds are most commonly
affected by type C and to a lesser extent type E.

Birds either ingest the toxin directly or may eat invertebrates (such
as chironomids [non-biting midges], fly larvae) containing the toxin.
Invertebrates are not affected by the toxin and store it in their
body. A cycle develops in a botulism outbreak when fly larvae
(maggots), feed on animal carcasses and ingest toxin. Ducks that
consume toxin-laden maggots can develop botulism after eating as few
as 3 or 4 maggots.

Healthy birds, affected birds, and dead birds in various stages of
decay are commonly found in the same area. The toxin affects the
nervous system by preventing impulse transmission to muscles. Birds
are unable to use their wings and legs normally or control the third
eyelid, neck muscles, and other muscles. Birds with paralyzed neck
muscles cannot hold their heads up and often drown. The disease has
occasionally been called "limberneck". Death can also result from
water deprivation, electrolyte imbalance, respiratory failure, or
predation.

Portions of this comment have been extracted from
http://www.nwhc.usgs.gov/disease_information/avian_botulism. -
Mod.TG]

See Also