402 



Hidihin Influences — Our Living Resources 



Avian botulism now occurs all over the 

 United States (Fig. 2) and in many other cotin- 

 tries as well. Because of the visibility of mas- 

 sive die-offs. avian botulism is probably the 

 best-documented nonhunting waterfowl mortal- 

 ity (Stout and Coniwell 1976). The continued 

 reporting of avian botulism die-offs since the 

 early I900"s makes researchers suspect that 

 much of the disease's geographic expansion is 

 of recent origin. Also, most (13 of 21) initial 

 outbreaks of avian botulism in countries other 

 than in North America have occuned since 

 1970. 



Avian Cholera 



Avian cholera, caused by the bacterium 

 Pasteiirella imiltocida, has been recognized as 



Fig. 2. Known distribution of "western duck sickness" (avian botulism) in North America. 

 (Kaimback and Gunderson 1934). and from 1975 to 1993. 



19.U 



Fig. 3. Geographic distribution of avian cholera in wild waterfowl within the United States, 

 before 1960 (first outbreak in 1944). dunng the 1960's. and after 1970, when disease spread 

 (National Wildlife Health Center files). 



an important infectious disease of domestic 

 poultry in the United States since at least 1867 

 (Rhoades and Rimler 1991). Therefore, it is 

 noteworthy that a 1930 evaluation of the status 

 of waterfowl commented on the lack of docu- 

 mentation of avian cholera in wild waterfowl 

 (Phillips and Lincoln 1930). In 1944, however, 

 the disease was documented in wild waterfowl 

 in the United States (Quortrup et al. 1946). 

 Limited geographical expansion of avian 

 cholera in wild waterfowl occurred during the 

 1940"s and 1950"s, and sporadic occurrences 

 were documented at a few new locations during 

 the 1960"s (Fig. 3). By the end of the 1960"s, 

 though, avian cholera was reported as estab- 

 lished in the Central and Pacific tlyways. 

 Outbreaks in the Mississippi Flyway were 

 unusual, and only two outbreaks had occurred 

 in the Atlantic Flyway. With the exception of a 

 single instance during the breeding season, out- 

 breaks occurred in winter (Stout and Comwell 

 1976). During the 1970"s, avian cholera became 

 established as a major cause of waterfowl mor- 

 tality in all four flyways within the United 

 States and as a recurring cause of waterfowl 

 mortality in Canada (Fig. 3). Geographic expan- 

 sion of die-off locations continues, and out- 

 breaks now occur during all seasons of the year 

 (Friend 1987). 



Duck Plague 



Duck plague is another emerging disease of 

 North American waterfowl. This heipesvirus 

 infection first appeared on the North American 

 continent in 1967 when it caused large-scale 

 losses in the domestic duck industi7 and losses 

 of a small number of wild waterfowl (Leibovitz 

 and Hwang 1968). The first major die-off 

 involving wild waterfowl occurred during 

 January 1973 at the Lake Andes National 

 Wildlife Refuge in South Dakota (Friend and 

 Pearson 1973). Duck plague has expanded 

 throughout North America since the initial out- 

 break, along with an increasing number of out- 

 breaks in each decade (Fig. 4). Nearly all occur- 

 rences of duck plague have involved nonmigra- 

 tory waterfowl (captive, tame, and resident 

 waterfowl that do not undergo traditional 

 migratory movements). A February 1994 out- 

 break in the Finger Lakes region of New York 

 State involving mallards (Anas pUnyrliynchos) 

 and American black ducks (A. nibripes) is the 

 first major outbreak involving migratory water- 

 fowl since the January 1973 Lake Andes out- 

 break. 



Other Diseases 



Other diseases affecting wild birds are newly 

 recognized, are occurring with increasing fre- 

 quency, or have expanded their geographic 



