Wildlife officials have confirmed the presence of a parasitic flatworm in wild swans from Wolf Lake. Diagnostic testing was conducted at the U.S. Geological Survey’s (USGS) National Wildlife Health Center in Madison, Wisconsin.
Mute swans examined by the USGS had fatal infections of the intestinal parasite Sphaeridiotrema globulus. This parasite causes death in many species of waterfowl, including swans, diving ducks, and coots. Lead testing was also performed on the swans, and results were within the range of nontoxic background levels.
The cause of death of the Canada geese collected from the same area could not be determined, despite extensive testing. The geese tested negative for bacterial and viral infection, lead poisoning, heavy metals, salt toxicity, botulism, and toxic organic compounds. All birds tested negative for avian influenza.
“Wildlife disease investigations can be challenging, especially when multiple factors, including adverse weather conditions, may be involved,” said USGS scientist Julia Lankton. “While we could not confirm a cause of mortality for the Canada geese, we are glad that the mortality event seems to have resolved and dead birds are no longer being reported.”
Peak mortality in Canada geese was observed over a period of approximately a week in late February after a period of severe cold weather, and deaths subsided in early March. Mute swan deaths were not observed until early March.
“The DNR, together with state, federal and private partners, has been monitoring migratory bird populations in the area and mortality seems to have subsided” said Mitch Marcus, fish & wildlife health supervisor for the Indiana DNR Division of Fish & Wildlife.
The parasite that infected the swans poses no known risk to humans, pets, or the commercial poultry industry. Snails consumed by swans and other waterfowl serve as an intermediate host for the parasite. Infected birds may appear weak or unable to fly and often die. Control measures have not been developed for this parasite, and waterfowl deaths may recur on a regular basis.
Animals known or suspected to be ill should not be consumed. Anyone who sees sick or dead wildlife is encouraged to report it to the DNR using the online reporting tool at on.IN.gov/sickwildlife.
To view all DNR news releases, please see dnr.IN.gov.