Zoonotic pathogens can harm human health and wellbeing directly or by impacting livestock. Pathogens that spillover from wildlife can also impair conservation efforts if humans perceive wildlife as pests. Brucellosis, caused by the bacterium Brucella abortus, circulates in elk and bison herds of the Greater Yellowstone Ecosystem and poses a risk to cattle and humans. Our goal was to understand the relative effects of climatic drivers, host demography, and management control programs on disease dynamics.
Synthesis and applications: Positive serostatus is often weakly correlated with infectiousness but is nevertheless used to make management decisions including lethal removal in wildlife disease systems. We show how this can have adverse consequences whereas efforts that maintain herd immunity can have longer-term protective effects. Climatic drivers may not result in synchronous disease dynamics across populations unless vital rates are also similar because demographic factors have a large influence on disease patterns.
Author ORCID Identifier
Gavin G. Coterill https://orcid.org/0000-0002-1408-778X
Johan T. du Toit https://orcid.org/0000-0003-0705-7117
Paul C. Cross https://orcid.org/0000-0001-8045-5213
.cvs, .RData, .rda, .R, .txt
.Rdata, .rda, and .R require software capable of reading R software.
U.S. Geological Survey
Rocky Mountain Elk Foundation
Utah State University
U.S. Geological Survey G16AC00106; Rocky Mountain Elk Foundation UT140699
Using >20 years of serologic, demographic, and environmental data on brucellosis in elk, we built stochastic compartmental models to assess the influences of climate forcing, herd immunity, population turnover, and management interventions on pathogen transmission. Data were collected at feedgrounds visited in winter by free-ranging elk in Wyoming, USA.
Snowpack, hypothesized as a driver of elk aggregation and thus brucellosis transmission, was strongly correlated across feedgrounds. We expected this variable to drive synchronized disease dynamics across herds. Instead, we demonstrate asynchronous epizootics driven by variation in demographic rates.
We evaluated the effectiveness of test-and-slaughter of seropositive female elk at two feedgrounds. Test-and-slaughter temporarily reduced herd-level seroprevalence but likely reduced herd immunity while removing few infectious individuals, resulting in subsequent outbreaks once the intervention ceased. We simulated an alternative strategy of removing seronegative female elk and found it would increase herd immunity, yielding fewer infections. We evaluated a second experimental treatment wherein feeding density was reduced at one feedground, but we found no evidence for an effect despite a decade of implementation.
Cotterill, G.G., Cross, P.C., Merkle, J.A., Rogerson, J.D., Scurlock, B.M. and du Toit, J.T. (2019), "Parsing the Effects of Demography, Climate, and Management on Recurrent Brucellosis Outbreaks in Elk." J Appl Ecol. doi:10.1111/1365-2664.13553
Greater Yellowstone, WY
See ESM_README.txt and pomp_README.txt for variables.
file: 'covar.csv' definitions:
'Feedground' = subpopulation
'cyear' = capture year
'MJ' = March to June cumulative snowmelt water equivalent from nearest SNOTEL site, standardized by site and exponentiated
'std_springStart' = standardized and exponentiated spring start
'tot' = the number of serological tests in a given year
'pop' = the yearling and adult female elk count in a given year
'births' = the number of calves counted at the feedground during peak winter, divided by two under the assumption of equal sex ratios.
file: 'dat.csv' definitions:
"Feedground' = subpopulation
'dyear' = capture year
'pos' = the number of seropositive tests in a given year
'apparent' = the apparent seroprevalence (pos/tot)
'dpop' = the yearling and adult female elk count in a given year.
Natural Resources and Conservation
This work is licensed under a Creative Commons Attribution 4.0 License.
Coterill, Gavin G.; du Toit, Johan T.; and Cross, Paul C., "Supplemental material for Cotterill et al. 2020: Parsing the effects of demography, climate, and management on recurrent brucellosis outbreaks in elk. Journal of Applied Ecology." (2019). Browse all Datasets. Paper 92.
Additional FilesESM_README.txt (4 kB)
ESM.zip (94451 kB)
unif_births.R (7 kB)
covar.csv (5 kB)
dat.csv (2 kB)
pomp_README.txt (1 kB)
dell_m0.R (9 kB)
greys_m0.R (9 kB)
muddy_m0_swe_04Aug.RData (7686 kB)
muddy_m0_swe_global_04Aug.rda (386 kB)
muddy_m0_swe_lik_local_04Aug.rda (1 kB)
muddy_m0_swe_local_04Aug.rda (7293 kB)
muddy_m0_swe_params_04Aug.csv (26 kB)
muddy_m0_interp.R (40 kB)
muddy_m0_run.R (10 kB)
muddy_m1_swe_04Aug.RData (10261 kB)
muddy_m1_swe_global_04Aug.rda (508 kB)
muddy_m1_swe_lik_local_04Aug.rda (1 kB)
muddy_m1_swe_local_04Aug.rda (9746 kB)
muddy_m1_swe_params_04Aug.csv (28 kB)
muddy_m1_interp.R (10 kB)
muddy_m1_run.R (10 kB)
muddy_m2_swe_04Aug.RData (8031 kB)
muddy_m2_swe_global_04Aug.rda (400 kB)
muddy_m2_swe_lik_local_04Aug.rda (1 kB)
muddy_m2_swe_local_04Aug.rda (7622 kB)
muddy_m2_swe_params_04Aug.csv (26 kB)
muddy_m2_interp.R (9 kB)
muddy_m2_run.R (9 kB)
muddy_m0_04Aug_unc_SIRR_04Aug19.RData (11072 kB)
muddy_m0_04Aug_unc50_TAS_comparisons_04Aug19.RData (21207 kB)
muddy_m0_04Aug_uncertain_04Aug19.RData (12547 kB)
unc_SIRR_run.R (5 kB)
unc_TAS_run.R (22 kB)
uncertain_interp.R (11 kB)
uncertain_run.R (5 kB)