Avian Cholera

Avian Cholera

by Colleen Grzan, [email protected]


There has been a massive outbreak of avian cholera at the Klamath Basin National Wildlife Refuge (includes Tule Lake, Clear Lake, Klamath Lake, Bear Valley), which spans the California-Oregon border.  This refuge is an important habitat for native and migratory birds such as golden and bald eagles, snow and Canada geese, white pelicans, ospreys, peregrine falcons, white-faced ibises, sandhill cranes, snowy and great egrets, great blue herons, and many species of ducks.


Though the disease is prevalent and cyclical, appearing every year across the country, this is the worst it’s been in the last 10-15 years at the Klamath area.  Already, over 10,000 dead water fowl have been picked up and removed.  The speedy removal of bodies is supremely important to controlling the outbreak as the disease is highly contagious and is transmitted by bird-to-bird contact and ingestion of food and water containing the bacteria.  Death is extremely rapid, usually occurring within 6-12 hours after a healthy bird has become infected, but sometimes so quickly that the birds actually fall out of the sky.  The most commonly affected birds are ducks, geese, coots, and gulls.  Some sick birds may exhibit strange behavior as lethargy, convulsions, swimming in circles, or erratic flight, such as flying upside down.


A significant cause of the outbreak is overcrowding.  Millions of water fowl pass through the refuge during spring migration.  But because of this year’s relatively dry winter and spring, the water level of ponds, marshes, and lakes has been low, causing the birds to closely congregate in smaller areas.   The recent rains plus an influx of water from the Bureau of Reclamation is helping to expand the wetlands and thus give the bird population the space it needs.


Why is this important to you?  Though there has not been an outbreak of cholera in the South Bay Area, one should be aware of the possibility occurring in the future, especially during droughts and because of habitat destruction.  If you notice an excessive amount of dead birds in or around ponds, contact your local California Dept. of Fish & Game office (707-944-5500) or the dead bird hotline (1-800-491-1899) or the National Wildlife Health Center (608-270-2447, [email protected]).  Wear gloves and place the birds in plastic bags.


Avian cholera does NOT pose a health threat to humans; however, it IS transmittable to domestic chickens, turkeys, geese, and ducks.