[MARINE_BIOLOGY_INTERNATIONAL] BOTULISM, AVIAN - USA: (CALIFORNIA)

 

BOTULISM, AVIAN - USA: (CALIFORNIA)
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Date: 28 Apr 2012
Source: Appeal-Democrat.com [edited]
<http://www.appeal-democrat.com/news/lake-115784-botulism-ducks.html>

Ellis Lake appears to be experiencing a new outbreak of avian botulism, Marysville police said Saturday [28 Apr 2012].

The police and public works departments have responded to multiple calls of dead and dying ducks around the lake in the last week, police said in a statement.

Avian botulism is a toxin that affects the central nervous system and causes gradual paralysis so that birds cannot hold their heads up and often drown. The toxin is not uncommon in the area, and it tends to be widespread in areas with an overpopulation of ducks, police said.
Warmer weather is a precursor of the toxin, but the toxin does not reflect the water quality.

Algae, especially algae rotting in high temperatures, is what usually leads to avian botulism outbreaks, according to the U.S. Geological Service. Reducing available oxygen, the vegetation helps kill off animals and invertebrates, allowing the botulism bacteria to activate and produce toxins.

Often, dead ducks provide the protein source for maggots that carry the toxin, and the maggots are then eaten by ducks to perpetuate the botulism cycle.

In June and July 2010, more than 30 dead ducks were spotted at the lake, with botulism believed to be the cause.

At the time, city officials said Ellis Lake has an inherent duck problem, as waterfowl arrive during migration and stay because people feed them. The lake, primarily fed by storm drains and no fresh water, is not that clean to begin with, and the high duck population worsens the situation.

In years past, the city relocated some waterfowl from Ellis Lake to keep existing populations healthy and to keep the flocks from becoming a nuisance. But the procedure, which requires trapping, transporting and releasing the animals, is labor-intensive.

Budget cutbacks in recent years also have minimized the amount of clean water the city pumps in and the frequency with which it is pumped. It would take roughly 30 days of constant pumping to change the existing water, city officials have said.

Police and public works are removing the dead ducks from the water and shoreline when located. Anyone who sees a dead or dying duck at Ellis Lake should call the Marysville Police Department at 749-3900.

[Byline: Ashley Gebb/ADagebb]

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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 3rd 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/>.

Ellis Lake, California may be found on the interactive HealthMap at:
<http://healthmap.org/r/2h_t>. - Mod.TG]

[see also:
2011
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Botulism, avian - USA (05): (CA) 20111115.3369 Botulism, avian - USA (04): (NV) 20111009.3031 Botulism, avian - USA (03): (CO) 20110925.2905 Botulism, avian - USA (02): (CO) 20110924.2888 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, avian - USA (02): (CO) 20100627.2145 Botulism, avian - USA: (MI) susp 20100618.2047] .................................................sb/tg/msp/lm/ll
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