State College Bird Club
October 26, 2016
State College Bird Club Meeting, October 26, 2016
Recording: Debra Grim
Checklist: 147 species reported
Treasurer report, Jean Miller: $660 received, $118 spent
Field trips: Bald Eagle State Park, TBA
Snow in Adirondacks may push ducks into our area.
November 16 meeting: The speaker will be Matt Toenies, a graduate
student in Ecology at Penn State, who will give a program entitled
"Winners and Losers in the
Changing Bird Community of Hemlock Forests."
October Speaker: Justin D Brown, DVM, PhD, Wildlife Veterinarian for
the Pennsylvania Game Commission, The Natural History of Avian
Influenza Virus in Wild Bird Reservoirs
Avian influenza has many combinations of subtypes H1-16 and N1-9,
differing in severity. Highly pathogenic types like H5 and H7 cause
80-100% mortality in chicken flocks. Wild bird populations preserve the
virus in a reservoir including more than 100 wild species, most
commonly waterfowl, terns and gulls, shorebirds. The birds usually show
no symptoms and carry low pathogenic types. The virus is constantly
changing and always circulating, occasionally spilling over to other
hosts such as chickens, pigs, or humans.
Big outbreaks in poultry that make the news are spread when domestic
poultry are kept outdoors or via sharing of equipment and movements of
people. Usually when the virus crosses from wild birds to poultry, it’s
in a highly pathogenic form. We don’t know why chickens and other
domestic poultry are so easily infected. Avian influenza costs millions
of dollars in bird loss and cleanup. Even low pathogenic forms of the
virus must be controlled in chickens.
S.E. Asia tends to maintain a reservoir because of the presence of wild
birds in markets, mostly outdoor flocks, and less inspection and other
safeguards. The virus can be carried from there to Europe and North
America by migrating birds. In North America, the main source is wild
birds. We need to learn to identify the pathogen in wild birds and
discover how it infects domestic poultry.
Waterfowl, particularly dabbling ducks, have been known since the early
1970’s to be a reservoir. The virus presents as an asymptomatic
intestinal tract infection and is easily shed via droppings into the
water, where it can survive for weeks to months. The peak of infection
is during pre-migration staging in summer, with 20-30% infection. This
level drops as the waterfowl move south and disperse. Ducks were
sampled in NW Minnesota in July through December 2007 and 2008; 27-35
subtypes of the virus were shown to be circulating. Birds sampled in
Lakes Erie and Pymatuning in Pennsylvania showed the same pattern of
peaking at fall migration.
Avian flu was discovered in shorebirds in the 1980’s. Studies show that
ruddy turnstones demonstrate 90% concentrations of the virus when they
gather in May at Delaware Bay, always a different type. It is thought
they acquire the virus at the Bay, then quickly become immune. Red
knots, however, arrive already carrying antibodies—it is not known
where they became exposed. Sanderlings have no antibodies—they are
either resistant or never exposed.
H13 and H16 is endemic in gulls, particular in pre-fledge chicks. Other
Laridae are not well studied. Geese and raptors are susceptible.
Terrestrial birds are not a good reservoir.
Surveillance needs to continue: watching for sick birds, sampling waterfowl, and testing dead birds of many kinds.
Minutes by Debra Grim