presentation at 2009 eid meeting in park city, utah
TRANSCRIPT
Agent-based Modeling, Functional Connectivity, and Disease Transmission in Felines
Jeff A. Tracey, PhDSue VandeWoude, PhDKevin R. Crooks, PhD
Colorado State University
Introduction
● Agent-based Modeling (ABM)
● Role of host behavior in the ecology of infectious disease
– Movement and contact– Habitat fragmentation due to urbanization
Our Study System
● Species:– Bobcats (Lynx rufus), mountain
lions (Puma concolor), domestic cats (Felis catus)
● Locations:– Southern California, Colorado,
Florida, ...● Diseases:
– FIV, plague, calicivirus, toxoplasmosis, others
Bobcats in Southern California
HABITAT
BOBCAT
NON-HABITAT
Questions
● How does movement behavior interact with habitat fragmentation to affect contact rates and spread of an SI disease?
● How does movement behavior and landscape structure affect the transmission of the disease within and between habitat patches?
Agent-based Models (ABMs)● a.k.a. Individual-based Models (IBMs)
● Agent-level:– Individual bobcats– Sensing, decisions, behavior– Interactions
● System-level: emergence; collect data, summarize
● “Computational laboratories”
Start Simple...
● No birth, death, or life history● No social interactions● Agents have same move rule● Simple SI, direct contact disease (FIV-like)
● Incrementally, we will add detail / specificity
ABM Components
● Landscape● Agents● Disease● Networks
– Contact– Disease– Later, will add social networks
Hig
hLo
w
High LowFragmentation
Hab
itat A
mou
nt
Movement Rules
● Parts of movement rule– Landscape response– Basic movement rule
● Basic movement rules:– Random– Home range-like– Dispersal-like
● More realistic rules...
Simulation Experiments
● Vary parameters– Disease
● Proportion of initially infective individuals● Probability of disease transmission
– Landscape● Amount of habitat● Fragmentation
– Movement● Non-habitat preference● Move rule and parameters
Agent Locations and State
Contact Network
Disease Network
Simulation Experiments
● Summarize system-level properties:– Proportion infective at end of simulation– Proportion of within-patch transmissions– Proportion of between-patch transmissions– Proportion of patches with infective individuals– many others...
Movement Behavior Matters
30 % Habitat
Variation Due to Movement Behavior Only
10 % Habitat
Variation Due to Movement Behavior Only
Effects of Movement Can Be Nonlinear
Example: Between patch transmission Highest at:● Intermediate non-
habitat permeability● Intermediate
directionality for dispersal-like movement
Landscape: highly fragmented, 30% habitat
Directionality
Fragmentation Does Not Always Slow Disease Spread
● Effects of landscape can have opposite effects on prevalence depending on movement
Dispersal-like Movement50 % Habitat
Landscape Change as a Dynamic Process
● Therefore:– Connectivity and
movement should change
– Disease dynamics should change
● More vulnerable at particular stages?
● Species-specific
Western Futures ModelsDr. Dave Theobald, CSU
Landscape Change as a Dynamic Process
● Therefore:– Connectivity and
movement should change
– Disease dynamics should change
● More vulnerable at particular stages?
● Species-specific
Western Futures ModelsDr. Dave Theobald, CSU
Landscape Change as a Dynamic Process
● Therefore:– Connectivity and
movement should change
– Disease dynamics should change
● More vulnerable at particular stages?
● Species-specific
Western Futures ModelsDr. Dave Theobald, CSU
Landscape Change as a Dynamic Process
● Therefore:– Connectivity and
movement should change
– Disease dynamics should change
● More vulnerable at particular stages?
● Species-specific
Western Futures ModelsDr. Dave Theobald, CSU
Important Points:
● Agent-based modeling approach– Computational laboratory
● Movement matters– Can be nonlinear, counter-intuitive
● Simulation software
Acknowledgments
Funding:● National Science
Foundation● Burroughs Wellcome
Travel Scholarship
Other CSU Team Members:● Mo Salman, Mike Lapin● Sarah Bevins● Justin Lee, Jesse Lewis,
Martha MacMillan, Linda Sweanor, Robert Alonso
Dr. Jun Zhu (UW-Madison/CSU)
Collaborators From:● UC Davis, University of Florida, San Diego
State University, US Geological Survey, NIH, CDC, NPS, USFWS, Colorado Division of Wildlife
Thank you to the conference organizers!
