Nation’s toll of bird flu this year worse than 2015 outbreak

The fall migration of geese is expected to peak this month in Iowa with the potential to cause further infections of domestic flocks by a highly pathogenic and destructive avian influenza.

The most recent detection of the virus among those flocks was late last week at a Buena Vista County commercial turkey facility with about 40,000 birds, according to the Iowa Department of Agriculture and Land Stewardship. It was the fifth detection in commercial or backyard flocks in Iowa this fall and the 24th for his year.

Wild, migrating birds are believed to be the primary source of the virus transmissions. The fall duck migration appears to be waning based on weekly state surveys, but the presence of Canada geese doubled last month.

About 20 wild ducks were found to be infected by the virus in November in Iowa, according to the U.S. Department of Agriculture. The ducks were shot by hunters in Clay, Jackson, Louisa and Monona counties. Infected wild geese were last discovered in Johnson County in September.

“It’s very difficult to predict the prevalence of avian influenza based solely on waterfowl activity,” said Orrin Jones, waterfowl biologist for the Iowa Department of Natural Resources. “How common is it out there? What types of birds is it affecting? This new strain is affecting a wider range of species and having a wider range of effects than previous strains. There’s still a lot of uncertainty.”

This year’s bird flu death toll of nearly 53 million fowl recently surpassed the total number of U.S. bird deaths in domestic flocks during the last outbreak of 2014-2015. Entire flocks of domestic birds are euthanized after a detection is found to help stop the spread of the disease.

That is primarily due to the virus’ reemergence in this fall. In the last outbreak — when more than 50 million birds were killed — new confirmed cases of deadly avian influenza stopped in June.

The virus infected 19 Iowa flocks from March to May this year and led to the deaths of about 13.4 million birds. It wasn’t identified in another Iowa flock for more than five months until the virus sickened a backyard flock in Dallas County in October.

There have been five flocks affected this fall with a total of more than 2.1 million birds. Most of them were from two Wright County facilities with egg-laying hens that had more than 1 million birds apiece.

The virus, while deadly to birds, does not pose a significant health risk to humans. The U.S. Centers for Disease Control and Prevention reported a human infection in April. The person helped cull an infected flock and reported feeling tired for several days but recovered.

Wild bird migration linked to infections

State agricultural officials have said waterfowl are the most likely drivers of bird flu infections among domestic flocks.

The Iowa DNR conducts weekly waterfowl surveys at about 20 sites across the state. Last week, it recorded the highest numbers of ducks and geese near Lake Rathbun in south-central Iowa, the Missouri River oxbows south of Sioux City, Lake Odessa near the Mississippi River in southeast Iowa, Riverton in southwest Iowa and in the Great Lakes area of northwest Iowa.

Jones, the waterfowl biologist, said the birds are more likely to stay close to rivers during winter months when ponds and lakes begin to freeze. They often roost on open water and feed on leftover grain in harvested fields, so snow and ice can force them to fly farther south. Larger birds like ducks and geese that can withstand harsher winter conditions are often the last to migrate south, Jones said.

In the past two weeks, the deadly bird flu has been detected in domestic flocks in most of Iowa’s neighboring states. The virus has been most prevalent in South Dakota, where 10 commercial turkey flocks with a total of nearly 550,000 birds have been affected.

Last month, Iowa barred live bird shows and the sale of birds at livestock auction markets, swap meets and other venues. The order will expire 30 days after a detection if there are no new detections during that time.

This article first appeared in the Iowa Capital Dispatch.