
HISTORY OF INCIDENCE AND LOSSES 
What appears to have been mortality from avian botulism in wild ducks was known 
before the great outbreak of 1910, but as one reviews records of die-offs before 
then, the basis for identifying botulism as the causative agent becomes less definite. 

Wetmore (1918) reported that "Sick ducks had been noticed in the Bear River 
marshes at the northern end of Great Salt Lake for many years, though the trouble is 
not known to have been serious until 1910." He stated further that "Some of the early 
settlers in this region have reported sick birds at earlier dates." Fisher (1893) 
reported finding many eared grebes and shovelers dead at Owens Lake, Calif., in June | 
1891. This mortality cannot definitely be laid to botulism, but is suggestive. 
Kalmbach and Gunderson (193) mention a still earlier and less detailed account by 
Loew of heavy avian mortality at this same California location. They considered, E 
however, that "the earliest records of true duck sickness that may be pointed to with 
reasonable assurance are those mentioned by Wetmore for the early nineties at Great 
Salt Lake." It appears probable that incidence of botulism in waterfowl greatly | | 
antedates authentic records of its occurrence. ; 

Actually, unquestioned diagnosis of avian botulism can be made only when the toxin) 
of Clostridium botulinum has been proved 1/ to be present in the blood of typically 
sick birds. In only a few instances has this been done. Reasonably accurate presump- 
tive diagnoses of the nature of epizootics can be made on the basis of symptoms in the 
individual sick birds, of findings at gross autopsy, of microscopical findings, and of | 
epizoological and ecological circumstances. An observer familiar with the character- 
istic mortality and morbidity patterns of this malady can distinguish large outbreaks 
of avian botulism in the field with reasonable certainty. Almost all of the epizooticg 
mentioned here have been diagnosed on the latter basis. 
i 
Since 1910, somewhat more reliable and detailed records on botulism incidence have 
become available. These show that duck sickness is known to occur in a great many |! 
locations throughout the western United States. Outbreaks have been reported from all | 
States west of the 100th meridian except Colorado and Oklahoma. They have occurred 
also in Minnesota, Wisconsin, Illinois, and Michigan. Several suggestive occurrences 
are known from Delaware, New York, Pennsylvania, and Virginia. In one of these, 
Clostridium botulinum, type C, was cultured from the liver of a black duck found paral- 
yzed near Dyke, Va., in December 1930 (Kalmbach, personal notes). 

In Canada, avian botulism has occurred at a number of points, some well north of | 
our border (Welstead Lake, Alta., 58° 30! N.), and at times with disastrous results. 
Formerly, Stobart Lake in southern Alberta, and more recently, Whitewater Lake in 
Manitoba, have been sites of severe outbreaks. 

_ 2rin 192], Wetmore’reported thé same or a very similar avian malady in Uruguay, | 
South America (Kalmbach, 193). E. M. Pullar (1934) reported a severe outbreak of 
botulism in the backwater of the Hume Reservoir, about 100 miles from Melbourne, 
Victoria, Australia, during their summer of 1932-33. He associated that outbreak with 
a closely related variant of the organism responsible for North American outbreaks. 
1/ Proved by intraperitoneal injection of suspected bird serum into antitoxin-protected] 
mice, and into nonprotected mice. In a case of botulism, the antitoxin-protected mice 
show no symptoms, while the unprotected mice sicken or die. 
owe | 
