Hi Gerry and Tweeters,

Several birders have posted recently on Tweeters about what is almost
certainly salmonellosis in Siskins (as Wayne Weber and probably others have
pointed out). There is no evidence that black oil sunflower seeds are an
important source; in last year's outbreak I tested seed samples of several
different brands from about a dozen birdfeeders who had dying finches, but
none of the seeds were detectably contaminated.

I believe that the birds themselves are the source. This Spring on the
Palouse, I found dead Siskins in the forest, miles from the nearest feeder,
infected with salmonellosis. I've found that Grosbeaks, Siskins, and
Cassin's Finches dead from window strikes are frequently culture positive as
well. In 1998/1999 I made a concerted effort to collect isolates from
birdfeeder salmonella deaths, and found a single strain of salmonella
(serotype Typhimurium, phage type u284) in finches ranging from the Canadian
border to Oregon, and from Washington to Montana. A similar epidemic strain
(phage type 40) in geographically dispersed birdfeeder salmonella deaths was
reported in 1998 in England.

Perhaps Siskin salmonellosis is a good example of the topic of a recent
review article in the journal Science entitled Emerging infectious diseases
of wildlife--threats to biodiversity and human health. (Jan
21;287(5452):443-9). These authors suggest that perhaps infectious diseases
play a role in population dynamics of wildlife more than was previously
recognized.

As Wayne pointed out, Siskins appear to be particularly susceptible to this
disease, but other finches also are often affected. Because concentrations
of animals in general tend to have more problems with salmonellosis than
dispersed populations, I think that if you find typical affected birds it
would be probably beneficial to stop feeding birds for a few months to let
the outbreak die down. I suspect that the main effect of this may be to move
the deaths to unobserved places, but it could also act to reduce the size of
the outbreaks.

Please remember that this disease is transmissible to humans, including you
(and especially your children). It's probably safer to stop feeding birds
when you see this condition simply to reduce the risk to your family's
health.

Tom Besser
___________________________________________________
Thomas E. Besser DVM PhD Phone:(509)335-6075
WA Animal Disease Diagnostic Lab FAX: (509) 335-8529
Pullman WA 99164-7040 tbesser at vetmed.wsu.edu


> -----Original Message-----
> From: Gerry [mailto:bearlair at whidbey.net]
> Sent: Wednesday, April 26, 2000 8:47 AM
> To: tbesser at vetmed.wsu.edu
> Subject:
>
>
> Dr. Besser, I was in touch with you last year about the dying
> Pine Siskens
> here on Whidbey Island. This winter I had no siskens until
> mid February,
> they seemed to be in good shape but soon a few started the
> "symptoms". I
> found maybe three or four dead and then all seemed OK. We
> recently moved to
> the east side of the island (from the west), bought all new
> feeders, food
> etc. The former owners, to the best of my knowledge did not
> feed the birds.
> Soon I had a multitude of eager birds including a great
> supply of siskens.
> Within days we started seeing signs of the disease! We are
> getting about one
> a day that exhibit the puffing out, feeding rapidly, and
> showing no fear
> etc. We do find dead ones occaisionally. My daughter who lives between
> Stevens Pass and Leavenworth tell s me she is experiencing
> the same. The
> only thing in common from our two houses and hers is black
> oil sunflower,
> could this be a problem? All other species are unaffected.
> Best, Gerry Smith
>