Some 2,000 migrating snow geese heading back to northern Alaska were found dead in Idaho this weekend and the likely culprit is avian cholera, according to Idaho Department of Fish & Game (IDFG) this week.

Snow geese Image/Boylan, Mike
Snow geese
Image/Boylan, Mike

Fish and Game officials say the carcasses were collected and will be incinerated so that other predatory and scavenger birds do not ingest the deadly bacteria. Results are not yet back from the IDFG Wildlife Laboratory to definitively confirm avian cholera, but apparent symptoms seem to indicate the disease. According to the United States Geographical Survey Health Laboratory, humans are not at a high risk of infection from the bacteria causing avian cholera.

The carcasses of a small number of snow geese were first reported at Camas National Wildlife Refuge near Dubois, Idaho. Closer inspection on Friday found higher numbers of dead birds at the Mud Lake WMA Area near Terreton, Idaho and a lesser amount at Market Lake WMA near Roberts, Idaho.

The migratory birds were on the return leg of their migration from the southwestern United States and Mexico to their breeding grounds on the northern coast of Alaska. It is unknown at this time where the geese may have picked up the suspected bacteria. “Outbreaks of avian cholera have occurred sporadically in the region over the past few decades,” said Upper Snake Regional Supervisor Steve Schmidt.

According to Schmidt, “The important thing is to quickly collect as many of the carcasses as possible, to prevent other birds from feeding on the infected birds.” In the case of Mud Lake WMA, biologists observed about twenty eagles in the vicinity of some of the carcasses. Because of a delayed incubation period it is uncertain where these eagles might be located, if and when the avian cholera affects them.

Avian cholera is a contagious, bacterial disease that affects domestic and wild birds worldwide. It usually occurs as a septicemia of sudden onset with high morbidity and mortality, but chronic and asymptomatic infections also occur.

Avian cholera in wild birds is primarily caused by the Pasteurella multocida strain, Type 1.

According to the USGS, large die-offs are seen primarily in wild ducks and geese where the disease affects birds peracutely. The sudden appearance of large numbers of dead birds in good body condition with few if any sick birds is observed.

Death may be so rapid that birds literally fall out of the sky or die while eating with no previous signs of disease. Sick birds appear lethargic, and when captured may die within minutes.

Other signs include convulsions; swimming in circles; throwing the head back between the wings; erratic flight, such as flying upside down or trying to land a foot or more above the water; mucous discharge from the mouth; soiling or matting of the feathers around the vent, eyes, and bill; pasty, fawn-colored or yellow droppings; or blood-stained droppings or nasal discharge.