Northern Prairie Wildlife Research Center
Environmental Characteristics Associated with the Occurrence of Avian
Botulism in Wetlands of a Northern California Refuge
by
Tonie E. Rocke1, Ned H. Euliss, Jr.2, and Michael
D. Samuel3
Abstract: Avian botulism is an important disease affecting many
species of waterbirds in North America, but the environmental conditions that
initiate outbreaks are poorly understood. To determine wetland attributes
associated with outbreaks of avian botulism in waterbirds at the Sacramento
National Wildlife Refuge (SNWR), California, we compared environmental characteristics
between wetlands where outbreaks occurred (outbreak wetlands) and did not
occur (nonoutbreak wetlands). In June through October, 198789, we monitored
the occurrence of avian botulism via observations for sick or dead sentinel
mallards (Anas platyrhynchos) placed in 4 wetland enclosures. During
this same time period, we collected environmental data from the water column
and sediments of each wetland enclosure at 1014-day sampling intervals.
Multivariate analysis was used to reduce 22 environmental variables to 7 factors
for inclusion in subsequent statistical analyses. We found that outbreak wetlands
had significantly lower redox potential than nonoutbreak wetlands. The probability
of botulism in sentinel mallards was associated with increasing temperature,
increasing invertebrate abundance or biomass, and decreasing turbidity. However,
because these factors were not consistently higher in outbreak wetlands compared
to nonoutbreak wetlands, they may have a more proximate effect in initiating
an outbreak.
Key words: Anas platyrhynchos, avian botulism, botulinum
toxin, Clostridium botulinum Type C, environmental characteristics,
sentinel mallards, waterfowl, wetlands.
This resource is based on the following source (Northern Prairie Publication
1056):
Rocke, T.E., N.H. Euliss, Jr. and M.D. Samuel. 1999. Environmental
characteristics associated with the occurrence of avian botulism in
wetlands of a northern California refuge. J. Wildl. Manage. 63(1):
358-368.
This resource should be cited as:
Rocke, T.E., N.H. Euliss, Jr. and M.D. Samuel. 1999. Environmental
characteristics associated with the occurrence of avian botulism in
wetlands of a northern California refuge. J. Wildl. Manage. 63(1):
358-368. Jamestown, ND: Northern Prairie Wildlife Research Center
Online. http://www.npwrc.usgs.gov/resource/birds/botulsm/index.htm
(Version 22JUL99).
Table of Contents
1U.S. Geological Survey, Biological Resources Division, National
Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711, USA
E-mail: tonie_rocke@usgs.gov
2U.S. Geological Survey, Biological Resources Division, Northern
Prairie Science Center, 8711 37th Street Southeast, Jamestown, ND 58401, USA
3U.S. Geological Survey, Biological Resources Division, National
Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711, USA
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