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International Society for Infectious Diseases <http://www.isid.org>

Date: Wed 4 Jan 2012
Source: The MetroWest Daily News [edited] <http://www.metrowestdailynews.com/news/x1896001178/State-investigating-deaths-of-16-swans-in-Westborough#ixzz1ig6OZXjD>

State biologists are unsure what caused the deaths of about 16 swans near Mill Pond late last month [December 2011], but say it is unlikely the cause would be harmful to humans.

"I don't think there are any human health hazards," said H. Heussmann, a state waterfowl biologist. "There are very few viruses associated between humans and waterfowl."

Police say a caller reported seeing 5-6 dead swans floating in Mill Pond on 17 Dec 2011. A total of 16 dead swans were located in the area, said Massachusetts Fisheries and Wildlife spokesman Reggie Zimmerman.

"The USDA Wildlife services have taken tissue samples (of the dead swans), and we're waiting for some test results to come back," said Heussmann. "My suspicion would be it's some sort of virus, but that's total guesswork. We do know that they're not being shot."

Heussmann said it would take up to a month to get the lab results back and determine the cause of the birds' deaths. "Often by the time we determine the cause of a disease outbreak, it's over," Heussmann said.

The state has been working to replace a dam on Mill Pond, but Heussmann said the construction did not contribute to the swans'
deaths. He said in other parts of the state, he has seen die-offs of Canada geese from lead poisoning and other birds dying from botulism.

"I couldn't totally rule out lead poisoning," said Heussmann, "and botulism tends to be a warm weather disease, but there is the possibility."

Heussmann said that if the swans died of botulism, it would not affect humans.

[Byline: Kelleigh Welch]

Communicated by:
ProMED-mail from HealthMap alerts

[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.

Aquatic environments subject to intense hunting and/or fishing activities have been identified as high-risk areas for lead poisoning, because hundreds of lead pellets or fishing weights are introduced each season. The most frequent mode of exposure for waterfowl is through accidental ingestion of lead pellets that they confuse for seeds or grit.

Besides botulism and saturnism (lead poisoning), avian cholera is to be suspected. Avian cholera is the most important infectious disease affecting wild North American waterfowl, although it is much more common in western states, and it has not been reported in Massachusetts. This disease in waterfowl can occur any time of the year, although where it occurs annually, there is an established seasonal pattern. It is the result of infection with the bacterium _Pasteurella multocida_ (mainly serotype 1). The bacterium kills swiftly, sometimes in as few as 6-12 hours after infection. Live bacteria released into the environment by dead and dying birds, or by birds carrying the disease, can subsequently infect healthy birds. It is not considered a disease of public health concern.

More information on the associated pathology found in the dead swans will be helpful.

Portions of this comment were extracted from <http://www.nwhc.usgs.gov/publications/fact_sheets/pdfs/cholera091102.PDF>

A map of Westborough, Massachusetts can be accessed at <http://healthmap.org/r/1C4K>. - Mod.PMB]

[see also:
Lead poisoning, avian - Canada: (NS) eagles 20120106.0043
Botulism, avian - USA: (CO) 20110914.2797 Lead poisoning, avian - USA: (WA) trumpeter swan 20110204.0405 2010
Botulism, avian - USA (05): (FL) susp. 20100817.2848 Undiagnosed die-off, avian - USA (08): (CA) botulism susp.
Avian cholera - USA: (UT) (02) 20080406.1256 Avian cholera - USA: (UT) 20080104.0041] .................................................sb/pmb/msp/mpp/ll
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