Published Date: 2006-11-03 00:00:00
Subject: PRO/AH/EDR> Botulism, avian - USA (NY)
Archive Number: 20061103.3161

BOTULISM, AVIAN - USA (NEW YORK)
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A ProMED-mail post
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International Society for Infectious Diseases
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Date: 1 Nov 2006
From: Brent Barrett <salbrent@sbcglobal.net>
Source: Democrat and Chronicle.com [edited]
<http://www.democratandchronicle.com/apps/pbcs.dll/article?AID=/20061101/NEWS01/611010366/1002/NEWS>

Type E botulism seems to be the cause of scores of bird deaths last
month along a stretch of Lake Ontario shoreline, according to the
state Department of Environmental Conservation (DEC).
At least one sample taken from the bird carcasses has indicated that
type E was the cause of death, DEC spokeswoman Maureen Wren said;
other samples are pending. The necropsies, which are complete
postmortem examinations, also indicate that type E is the cause, she said.
Caused by the bacterium _Clostridium botulinum_, type E is a type of
food poisoning that typically affects fish-eating birds such as
loons. But the state is warning that the bird-killing toxin could
also harm humans who eat sick birds.
The bodies of the loons, gulls and grebes were first discovered on 21
Oct 2006 between Wayne County's Sodus Bay and Deer Creek Marsh in
Oswego County. The DEC's Wildlife Pathology Unit is inspecting and
testing the birds.
Avian botulism is a major cause of death in migratory birds,
according to New York Sea Grant. Type E botulism outbreaks have been
seen on the Great Lakes as far back as the mid-1960s on Lake
Michigan. But type E did not appear on Lake Ontario until 2002. And
this year has proven to be the most fatal to Lake Ontario wildlife,
with hundreds of birds dying in July from botulism along the coast of
Jefferson County on the eastern shore of Lake Ontario, according to the DEC.
Botulism killed an estimated 5000 birds on Lake Erie in 2000, and the
lake has seen bird deaths annually since then.
The state Health Department said in a statement it does not know of
any human cases of botulism related to the loon deaths.
The spores for type E botulism are naturally found in soil and
aquatic sediment, as well as the intestinal tracts of healthy
animals, according to Sea Grant. Birds get sick by eating fish
contaminated with type E botulism.
Scientists still aren't sure why botulism flares up and dies down, or
why recent outbreaks have been particularly calamitous, said Rod
Getchell, a professor in Cornell University's aquatic animal health program.
But one hypothesis is that the recent introduction of invasive
species such as gobies and zebra mussels might be changing the
ecology of the lake's bottom, he said, allowing the type E spores to germinate.
[Byline: Matthew Daneman]
--
Brent Barrett
<salbrent@sbcglobal.net>
[Botulism in avians is not usually type E, so this is an interesting case.
Though avian botulism is seen more often in other regions, it will
occur where the conditions are favorable.
The sporulating anaerobic gram-positive bacillus _C. botulinum_
elaborates 7 types of antigenically distinct neurotoxins, 4 of which
affect humans: type A, B, E, or rarely type F. Toxins types A and B
are highly poisonous proteins resistant to digestion by GI enzymes.
Approximately 50 percent of foodborne outbreaks in the USA are caused
by type A toxin, followed by types B and E.
Type C botulism occurs principally in waterfowl and other birds
living in an aquatic environment and causes tremendous losses, most
notably in waterfowl in the western US. In addition to North America,
it has been reported in birds in Europe, South Africa, Uruguay, and
Australia. In the Great Lakes region, it was first identified in 1936
in ducks on Green Bay of Lake Michigan and in 1941 in Monroe County
marshes along Lake Erie. Type C is most often associated with
limberneck paralysis in birds.
Type E botulism is connected with consumption of fish and occurs
mainly in gulls and loons, and to a lesser extent in mergansers, mute
swans, grebes, and shorebirds. It now appears that any birds or
mammals susceptible to botulinum toxin run a risk of becoming
poisoned if they scavenge dead fish. Evidence for this includes the
identification of type E toxin in a bald eagle, wood ducks, and
muskrats with fish remaining in their digestive tracts.
_C. botulinum_ spores are relatively heat-resistant, though high
temperatures and/or exposure to moist heat will kill the spores.
Toxins, on the other hand, are readily destroyed by heat and by
cooking food. Toxin production (especially type E) can occur at
temperatures as low as 3 degrees C (37.4 degrees F), i.e., inside a
refrigerator, and does not require strict anaerobic conditions.
Human illness from Type E is most often associated with improperly
smoked fish. Since the toxin is destroyed by heat, it appears that no
problem with botulism will result from eating cooked waterfowl.
(above information extracted from the Michigan Department of Natural
Resources website at
<http://www.michigan.gov/dnr/0,1607,7-153-10370_12150_12220-26493--,00.html>).
- Mod.TG]
...........tg/pg/mpp
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