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1. The major mortality waves in North America have occurred in areas of alkaline 
waters. The malady is further associated particularly with highly organic old-lake- 
bottom soils. 
2. There is frequent association of avian botulism with the reflooding of drying 
mud flats. 
3. Major outbreaks have seasonal periodicity; they occur practically always in 
sumer and early fall. In afew cases, smaller outbreaks have been reported in late 
fall and early spring, as thaw takes place. 
4. There is little species, sex, or age differentiation in mortality. Numbers 
of ducks affected seem to be in direct proportion to populations present. At Bear 
River, the shoveler is a minor exception to this general rule, as the mortality-to- 
population ratio exceeds slightly that found in other species of ducks. 
5. Nutritional condition seems to have little or no relation to the incidence of 
botulism. Most of the dead birds are in good flesh and often are quite fat. Stored 
fat is undoubtedly of real value to convalescing birds. 
6. Migrant birds seem particularly prone to intoxication, possibly because of 
heavy feeding activity after arrival from long flights. 
It is believed that wild ducks come in contact with type-C toxin through their 
feeding, or feeding activity. In this connection, it appears significant that surface- 
feeding ducks have sustained by far the greatest casualties from botulism. Ordinarily, 
such ducks feed or "puddle" in shallow water overlying silty, highly organic mud. 
Perhaps the most baffling phases of botulism have been the unpredictable timing 
and short duration of most outbreaks. An additional complication is the fact that the 
malady is dependent upon ingestion of an ephemeral biological toxin, not upon a tissue- 
invading organism or a stable inorganic poison. Also, it is difficult to imagine an 
experimental animal less amenable to experimental control and observation than a wild 
duck under natural conditions. Techniques used in studies of human botulism are not 
directly applicable to the comparable problem in waterfowl. 
PREVENTIVE AND REMEDIAL MEASURES 
Preventive measures against avian botulism are far more important, in the long run, 
than therapy. Batson (19l)\0) beliéved that ducks considered cured of their botulism 
intoxication did not survive long. Duck-banding returns from Bear River tend to support 
the idea that mortality among ducks recovered from botulism is higher than in unaffected 
birds. On the other hand, a group of birds hospitalized until apparently recovered and 
then held for an extended period on ponds at Salt Lake City (Williams and Jensen, 193) 
showed no excessive mortality. 
Many preventive measures have been suggested in the past. The most effective 
@xpedient know at present is water manipulation. This may vary from complete, tempor- 
ary drainage of marsh areas to deep flooding against steep impounding banks. There is 
little question that both of these measures are effective in preventing avian botulism. 
The unfortunate feature is that frequently these procedures may eliminate much of the 
feeding and nesting habitat required by waterfowl. 
He 
