An increase in the number of dead loons found on northeastern Minnesota lakes this summer is being blamed on West Nile Virus. The disease, which is transmitted by mosquitoes, has been identified as the cause of death of two out of three loons tested by the Department of Natural Resources and University of Minnesota.
Wildlife managers say there is no reason to be concerned about the overall loon population, but that it’s a good reminder that the virus is present in Minnesota and a risk to people and other wildlife in addition to the state bird.
“These two most recent loons are likely the first cases of disease and death due to West Nile virus infection this season in the state that we know about,” said University of Minnesota professor Arno Wuenschmann. “So this is a reminder that the virus is again active. People should use precautions that they have been told about for the past 15 or so years from MDH, and they should continue to vaccinate their horses.”
The disease has been present in the state since 2002, and caused loon deaths in 2005. While most people and animals that are infected can fight off the disease and develop antibodies that prevent future infections, some birds, like loons and crows are particularly vulnerable to the virus.
People infected with West Nile Virus often don’t experience any symptoms. But it can also cause flu-like symptoms, and can be particularly dangerous for elderly people. About 1 out of every 150 people who are infected develop dangerous symptoms. Last year, there were 63 human cases of West Nile Virus in Minnesota, including two deaths blamed on the disease.
Watching and waiting
The DNR says it will probably not test additional birds at this time, but if large numbers of dead loons are found, plans may change.
“Minnesotans love our loons and it’s concerning for people to find them dead. When we start seeing multiple birds dying on a single lake, we want to know about it so we can start tracking the information and determine when further testing is warranted,” said DNR nongame wildlife specialist Gaea Crozier. “While there isn’t a way to treat the West Nile virus infection, knowing the cause can help us rule out other, preventable causes of mortality.”
West Nile Virus overwinters in bird species including sparrows, finches, robins, canaries, and ravens. In late spring and early summer, the virus enters their bloodstream, where it can be carried by mosquitoes to other individuals.
Anyone who finds a dead loon is advised to use gloves and a plastic bag to collect the carcass, even though it’s not believed West Nile Virus can be transmitted that way, biologists recommend the practice for handing any dead animals. The birds can be disposed of in the trash or by being buried.
Anyone who finds two or more dead loons on a lake are asked to contact the local DNR nongame wildlife staff:
- Bemidji/northwest area: Christine Herwig
- Grand Rapids/northeast area: Gaea Crozier
- Metro/Central Minnesota: Lori Naumann
- New Ulm/southern Minnesota: Lisa Gelvin-Innvaer
The agency says that if reported loon deaths reach a threshold of concern, additional testing may be conducted.
More information:
- West Nile virus impacting Minnesota loon population – MN DNR
- West Nile virus rears its head in Minnesota loons – University of Minnesota
- West Nile virus – Centers for Disease Control and Prevention
- West Nile virus – Minnesota Department of Health