Abiotic predictors of avian botulism outbreaks in Utah

Avian botulism is a toxicosis responsible for large outbreaks in wild water fowl and wading birds. The toxin is produced by the bacterium Clostridium b otulinum type C. We gathered existing climatological and streamflow data fo r the Bear River Delta of northeastern Utah to determine effects of environ mental factors on probability of occurrence of an avian botulism outbreak. We built a logistic regression model using weather variables and streamflow amounts for 28 years, with a response variable if an outbreak occurred dur ing each year. Winter-summer precipitation amounts and summer streamflow we re predictors of outbreak probability (P<0.001). Outbreaks were more likely to occur during years of high winter-summer precipitation and high Bear Ri ver flows during summer. We concluded that these outbreak predictors may co ntribute to water-level fluctuations in managed wetland units, associated p reviously with outbreaks in this and other systems.