Avian Cholera News
Update: The avian cholera outbreak that recently caused the death of thousands of birds on the Great Salt Lake (GSL) appears to be over. Two mortality events in November and December, about 15 miles apart, affected mainly eared grebes, northern shovelers, California gulls, and green-winged teal. Eared grebes began dying around November 6th near Promontory Point; by December 1, estimates were that about 15,000 grebes out of a flock of 1.5 million died. Further south, near the town of Saltair, another die-off began around December 17 that affected grebes, green-winged teal and northern shovelers. About 1,500 birds died in this area. Avian cholera die-offs on the GSL are fairly common: in 1994, 15,000 birds died; in 1995, 1,000 birds perished; in 1998, 44,000; in 2002, nearly 30,000, and in 2004, again nearly 30,000. The USGS National Wildlife Health Center has been involved with helping Utah wildlife officials investigate many of these disease outbreaks.
Most species of birds and mammals can become infected with different
strains of Pasteurella multocida; however, avian cholera in wild birds is
primarily caused by one strain, Type 1. The species of birds most
commonly affected are ducks and geese, coots, gulls, and crows.
The bacteria can be transmitted by bird-to-bird contact, contact
with secretions or feces of infected birds, or ingestion of food or water
containing the bacteria. Aerosol tranmission may also occur. The bacteria
may survive up to 4 months in soil and water.
Clinical Signs/Field Signs
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.
Hemorrhages may be seen on the heart, liver, gizzard, and intestines. Areas
of tissue death appear as white or yellow "spots" on the liver and spleen.
The liver may appear darkened or copper in color, and may be swollen and
rupture when handled. These lesions are indicative of an acute disease process
and are not unique to avian cholera infection. The upper digestive tract may
contain recently ingested food, while lower digestive tract may contain a thick
yellowish viscous fluid that contains large numbers of P. multocida bacteria.
Wildlife Management Significance
Avian cholera is highly contagious and can spread rapidly. Prompt action
is needed to prevent and minimize the spread of the disease. Careful carcass
collection and disposal helps reduce the amount of bacteria in the environment.
Recommendations are site specific. Contact the National Wildlife Health Center for more information.
For additional information on this or any other wildlife health topic,
contact the National Wildlife Health Center at (608)270-2400.
Public Health Significance
Humans are not at a high risk for infection with the bacterial strain causing
avian cholera. Wearing gloves and thoroughly washing hands is recommended
when handling these birds or any sick or dead animal.
For a map of cholera in wild birds through 2004:
You can also see the National Atlas's dynamic map of avian cholera here
- Go to the National Atlas
- Click on the yellow 'Map Maker' button in the menu
- Select: 'Biology' > 'Wildlife Mortality' >
- Click on the blinking 'Redraw map' button above the side menu