BOTULISM, AVIAN - USA (04): (NV)
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Date: 8 Oct 2011
Source: The Republic [edited]
<http://www.therepublic.com/view/story/d609a4ecd19b4db3aa18f8641a714aff/NV--Bird-Deaths-Disease-Outbreak/>
An avian botulism outbreak has resulted in the deaths of nearly 2000 ducks and other birds at a private hunting lake near 2 of Nevada's most important wetlands for birds.
The Reno Gazette-Journal reports the die-off has occurred since late August 2011 at Six Man Club, a private lake near both the Stillwater National Wildlife Refuge and the state-run Carson Lake and Pasture.
The 2 wetlands, located around Fallon about 60 miles east of Reno, are major stops on the Pacific Flyway for a wide variety of migrating birds. Although birds frequently fly between the 3 water bodies, officials say the outbreak has not spread to Stillwater or Carson Lake.
They say an abundance of fresh water in Stillwater and Carson Lake could help prevent its spread there.
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[Avian botulism is a paralytic disease caused by ingestion of a toxin produced by the bacteria, _Clostridium botulinum_. This bacteria is widespread in soil and requires 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 _C. botulinum_; 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 (e.g.
chironomids, 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 and other birds 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. Death can also result from water deprivation, electrolyte imbalance, respiratory failure, or predation.
Prompt removal and proper disposal of carcasses by burial or burning (in accordance with applicable ordinances) is highly effective in removing toxin and maggot sources from the environment. If possible, avoid altering water depth by flooding or drawing down water levels during hot weather. This may increase invertebrate and fish die-offs, a protein source for the bacteria.
Providing mildly affected birds with fresh water, shade and protection from predators may help them recover from the intoxication. Botulism antitoxin is available but requires special handling and must be given early in the intoxication. Birds that survive a botulism outbreak are NOT immune to botulism toxin.
Portions of this comment were extracted from:
<http://www.nwhc.usgs.gov/disease_information/avian_botulism/>. - Mod.TG]
[see also:
Botulism, avian - USA (03): (CO) 20110925.2905 Botulism, avian - USA (02): (CO) 20110924.2888 Undiagnosed die-off, avian - USA (08): (CA) botulism susp.
20110923.2878
Botulism, avian - USA: (CO) 20110914.2797 2010
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Botulism, avian - USA (05): (FL) susp. 20100817.2848 Botulism, avian - USA (04): (OH) 20100718.2407 Botulism, avian - USA (03): (CA) 20100709.2294 Botulism - USA: canned tuna, risk, recall 20100708.2280 Botulism, avian - USA (02): (CO) 20100627.2145 Botulism, avian - USA: (MI) susp 20100618.2047] .................................................sb/tg/msp/ml/ll
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