This study used an agent-based model to simulate the transmission of foot-and-mouth disease virus (FMDV) in cattle herds in Cameroon, Africa. The model assessed both indirect transmission through contaminated environments and direct cattle-to-cattle contact. The model results supported three hypotheses: 1) epidemics occurred when indirect transmission was included, 2) direct transmission caused over 50% of infections, and 3) indirect transmission influenced disease dynamics by increasing infections seasonally when environmental contamination was highest. The findings suggest herd mobility impacts transmission and that indirect transmission plays a role in the endemic nature of FMDV in tropical regions.

1. PREDICTING FOOT-AND-MOUTH DISEASE VIRUS IN TROPICAL ENDEMIC
SETTINGS USING AN AGENT-BASED MODELING FRAMEWORK
Sarah Mielke1, Rebecca Garabed1, and Laura Pomeroy2
The Ohio State University
1College of Veterinary Medicine/Dept. Veterinary Preventive Medicine ; 2 College of Public Health
INTRODUCTION
Foot-and-Mouth Disease virus (FMDV) the causative agent of foot-and-
mouth disease (FMD), is a high priority infectious disease that requires
extensive planning in disease-free countries and zones to develop and
maintain prevention and control strategies. Although the virus and disease
have been intensively studied, viral persistence in tropical environments, has
largely been overlooked and assumptions regarding viral persistence are
primarily based on limited data from decade’s old research. We used agent-
based modeling (ABM) methods to assess indirect – focused on fomite and
direct – cattle to cattle contact, routes of transmission for FMDV.
Model Output to Address Hypotheses
Hypotheses
H1) FMD epidemics will be predicted when indirect transmission is included.
H2) Direct transmission will contribute more to total infections
than indirect transmission.
H3) Indirect transmission will influence
disease dynamics
Literature was used to compare mobile herd data for validation
Model Output
Susceptible Infected Recovered Contamination RH Month
Calculated Output
Indirect
Infections
Direct
Infections
Contamination Indirect Contribution
H1,H2 Literature Comparison.
H3
STUDY REGION: FAR NORTH CAMEROON
0
10
20
30
40
50
60
70
80
90
1 2 3 4 5 6 7 8 9 10 11 12
AVERAGE WEATHER 2011
Average Temperature Average Humidity
Agent-Based Modeling (ABM) incorporates individual agents, in this case
mobile and sedentary cattle herds, and applies decision rules that allows
the system to adjust to each agent’s behavior. The goal of this type of
modeling is to investigate emergent patterns that result from variations
within a system. Our ABM was designed to assess the indirect and direct
routes of
transmission for FMDV, using density- and frequency-dependent S-I-R sub-
models, applied to a complex livestock System in Cameroon, West Africa.
METHODS
ANALYSIS AND RESULTS: Density-dependent
Increasing RH
Decreasing RH
Start Dry Season
Start Rainy Season
Above is the seasonal pattern and associated changes in RH that are represented
throughout the result figures.
H1: FMD epidemics will be predicted when indirect transmission is
included
Panel A includes an indirect and direct transmission factor. Panel B includes the
direct transmission factor, only
H2: Direct transmission will contribute more to total infections
Direct transmission accounts for >50% of infections for mobile and sedentary herds.
H3) Indirect transmission will influence disease dynamics
A. Infection pattern for both mobile
and sedentary herds
C. Seasonal patterns vary in mobile
herds compared to overall infection
trends, which Align with sedentary
herds
CONCLUSIONS
• Indirect transmission results in the emergence of a seasonal pattern of FMD outbreaks
• Direct transmission accounts for the majority of infections
• Model predictions suggest that environmental contamination increases the proportion
of indirect infection early in the dry season.
• The differences in proportion of indirect transmission by herd type and timing of direct
infections in mobile herds suggests that herd mobility influences transmission.
FUTURE DIRECTIONS
Investigating drivers of endemic disease, for example: transmission rates in temperate
epidemic versus tropical endemic regions. Specifically, is the rate of transmission faster in
temperate regions compared to tropical regions.
Density-dependent transmission
Indirect contribution
Median
(%)
Range
(%)
Sedentary 25 19 - 42
Mobile 1.2 0 - 47
Comparison to Literature
Indirect contribution Author
44% Bravo de Rueda1
B. Sedentary herds showing similar patterns
to figure A, for indirect (L) and direct
transmission (R).
.
D. The level of environmental contamination
increases when indirect transmission was
included.
.
Bibliography
1. Bravo De Rueda, C., De Jong, M. C., Eblé, P. L., & Dekker, A.
(2015). Quantification of transmission of foot-and-mouth
disease virus caused by an environment contaminated with
secretions and excretions from infected calves. Veterinary
Research, 46(1). https://doi.org/10.1186/s13567-015-0156-5
Acknowledgements
Funding:
College of Veterinary Medicine
USDA-CEAH
This work was funded by NSF grant DEB-1015908
as part of the joint NSF-NIH Ecology of Infectious
Disease program.