SEASONAL PREVALENCE OF CLOSTRIDIUM-BOTULINUM TYPE-C IN SEDIMENTS OF ANORTHERN CALIFORNIA WETLAND

The prevalence of Clostridium botulinum type C (% of positive sediment samples) was determined in 10 marshes at Sacramento National Wildlife Refuge (SNWR), located in the Central Valley of California (USA), whe re avian botulism epizootics occur regularly. Fifty-two percent of 2,2 00 sediment samples collected over an 18-mo period contained C. botuli num type C (both neurotoxic and aneurotoxic) which was present through out the year in all 10 marshes. The prevalence of C. botulinum type C was similar in marshes with either high or low botulism losses in the previous 5 yr. Marshes with avian botulism mortality during the study had similar prevalences as marshes with no mortality. However, the pre valence of C. botulinum type C was higher in marshes that remained flo oded all year (permanent) compared with marshes that were drained in t he spring and reflooded in the fall (seasonal). The prevalence of C. b otulinum type C declined in seasonal marshes during the dry period. Si milar declines did not occur in the permanently flooded marshes.