Avian cholera
Avian cholera is a common waterfowl disease that most frequently affects waterfowl and coots, followed by scavenger bird species and other water birds. It is caused by the bacterium, Pasteurella multocida, which is highly contagious among birds and swiftly spreads through large congregations of waterfowl. In North America, this disease was first reported in 1944 and is the cause of the large-scale mortality of waterfowl in many states.
While it is seen annually in western states, especially in Snow geese and Ross’s geese, it has only been documented occasionally in Wisconsin. Avian cholera was the cause of mortality of over 800 mallards and Canada geese on Horicon Marsh from the fall of 1979 to the spring of 1980 and over 3,800 double-crested cormorants in Green Bay in the fall of 2019.
TRANSMISSION
Transmission of the bacteria can occur through bird-to-bird contact or from infected carcasses, water, soil, boots and equipment. Birds that survive infection can become sources of infection with the potential to spread the bacteria throughout a flyway.
CLINICAL SIGNS
Affected waterfowl may become sick very rapidly and the first signs of an outbreak may be multiple dead birds. Sick birds may be weak, twist their heads and necks over their back, have convulsions, swim in circles and fly erratically.
DISEASE MANAGEMENT
Management includes monitoring areas with high concentrations of waterfowl for mortality and promptly removing sick and dead birds to reduce the spread of the bacteria. The bacteria are easily killed with most disinfectants, including 10% bleach.
PUBLIC HEALTH
The bacterial strain that affects birds does not generally affect people and the human disease known as cholera is not the same disease as avian cholera.