MHASpread is a comprehensive stochastic, multiscale transmission model designed to simulate epidemic trajectories of foot-and-mouth disease (FMD) and other multi-host pathogens across livestock farming networks. The framework integrates within-farm disease dynamics, spatial transmission processes, and realistic disease control interventions to enable rigorous evaluation of outbreak response strategies.
The model operates at two coupled scales:
- Within-farm scale: Individual-based SEIR dynamics for multiple host species
- Metapopulation scale: Network-level transmission via spatial kernels and animal movements
MHASpread is particularly suited for:
- Epidemiological research: Understanding multi-host disease dynamics and species-specific transmission
- Policy evaluation: Assessing the effectiveness and cost-efficiency of control strategies
- Emergency preparedness: Simulating outbreak scenarios and informing contingency planning
- International capacity building: Supporting training and knowledge transfer in disease surveillance and control
Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed livestock with significant economic and trade implications. FMD demonstrates complex transmission dynamics due to:
- Multi-host nature: Differential susceptibility and transmissibility across cattle, swine, and small ruminants
- Environmental persistence: Heterogeneous transmission via direct contact, aerosol, and fomites
- Spatial heterogeneity: Disease spread constrained by distance but facilitated by animal movements
- Species-specific traits: Varying latent periods, infectious periods, and recovery rates
MHASpread explicitly models these complexities to provide mechanistic insights into outbreak progression under diverse epidemiological and management scenarios.
MHASpread is built on a stochastic, SEIR-based framework with distinct compartments for each host species:
| Compartment | Definition |
|---|---|
| S | Susceptible: animals not infected and able to acquire infection |
| E | Exposed: infected but not yet infectious (latent period) |
| I | Infectious: infected animals capable of transmitting infection |
| R | Recovered: animals recovered with temporary or permanent immunity |
| V | Vaccinated: animals with vaccine-induced immunity |
Disease progression within farms follows species-specific transmission probabilities (β) and disease duration parameters:
- Transmission coefficient (β): Determined by both infected and susceptible species, reflecting differential transmissibility (e.g., swine are more efficient FMD spreaders than cattle)
- Latent period (σ): Average 2–5 days, species-dependent
- Infectious period (γ): Average 3–6 days, species-dependent
- Vital dynamics: Births and deaths incorporated where data available
Local spread between farms is modeled using an exponential transmission kernel:
where:
-
$d_{ij}$ = distance between farms (maximum 40 km) -
$\phi$ = baseline transmission probability (0.044) -
$\alpha$ = kernel decay parameter (0.6) -
$I_i(t)/N_i$ = infection prevalence at farm$i$
This formulation captures the empirically observed pattern of decreasing transmission risk with distance, bounded by documented maximum dispersal distances.
Infected farms are detected through active surveillance using a hypergeometric sampling process that:
- Inspects a fraction of farms under surveillance (≥1 farm)
- Identifies infected farms accounting for finite surveillance population
- Incorporates diagnostic imperfection (sensitivity
$s$ ) - Tracks traceback-identified farms through contact tracing
MHASpread implements four primary control strategies:
| Control | Description | Implementation |
|---|---|---|
| Depopulation | Culling of infected farms | Priority by herd size; daily capacity limits |
| Emergency Vaccination | Ring vaccination of bovine herds | Infected + buffer zones; 15-day lag; daily capacity limits |
| Movement Standstill | Restriction on animal movements | 30-day duration across infected, buffer, and surveillance zones |
| Contact Tracing | Identification of linked farms | 30-day traceback window; farms under enhanced surveillance |
Three nested zones enforce differential surveillance and intervention intensity:
- Infected zone (3 km): Focus of depopulation and immediate control
- Buffer zone (7 km): Secondary vaccination prioritization
- Surveillance zone (15 km): Active detection and monitoring
✓ Multi-host dynamics: Explicit modeling of cattle, swine, and small ruminants
✓ Species-specific transmission: Parameterized from empirical literature
✓ Stochastic processes: Incorporates uncertainty in transmission, detection, and control efficacy
✓ Spatial heterogeneity: Distance-dependent transmission and realistic farm networks
✓ Flexible control actions: Customizable intervention timing, capacity, and extent
✓ Diagnostic imperfection: Reflects real-world detection limitations
✓ Vital dynamics: Optional incorporation of births and deaths
✓ Scenario analysis: Supports evaluation of multiple strategies
MHASpread has been applied to:
- FMD preparedness in South America: Evaluating control strategies for Brazil (2024) and Bolivia (2023)
- Cost-effectiveness analysis: Integrating epidemiological and economic models to inform policy
- Surveillance optimization: Assessing detection capacity and traceback effectiveness
- International training: Building epidemiological modeling expertise in partner countries
The MHASpread framework has been instrumental in international workshops and capacity-building initiatives aimed at strengthening disease surveillance and control expertise among veterinary and public health authorities in Latin America.
workshop_aftosa_chile_2024
Training program for Chilean national authorities on FMD simulation modeling, risk-based surveillance design, and emergency response preparedness. Participants gained hands-on experience with MHASpread to evaluate control strategies tailored to Chilean agricultural contexts.
PANAFTOSA-Workshop-Rio2023
Regional capacity-building initiative hosted by PAHO's Pan American Animal Health Organization, bringing together epidemiologists and veterinary officials from across the Americas. Focus on metapopulation modeling, uncertainty quantification, and evidence-based contingency planning for transboundary animal diseases.
MHASpread_workshop_PAHO
Comprehensive open-access workshop materials including tutorials, datasets, and worked examples. Provides reproducible workflows for disease simulation, sensitivity analysis, and policy evaluation using MHASpread-based methodologies.
MHASpread development and application are documented in peer-reviewed publications:
-
Cespedes Cardenas & Machado (2024): Modeling foot-and-mouth disease dissemination in Brazil and evaluating the effectiveness of control measures — Frontiers in Veterinary Science
-
Cardenas et al. (2024): Integrating epidemiological and economic models to estimate the cost of simulated foot-and-mouth disease outbreaks in Brazil — Preventive Veterinary Medicine
-
Cespedes & Castillo (2023): Foot-and-mouth disease in Bolivia: Simulation-based assessment of control strategies and vaccination requirements — Transboundary and Emerging Diseases
- Spatial scope: Model designed for farm-level networks; may require adaptation for larger-scale systems
- Data requirements: Accurate population sizes, movement records, and species composition needed
- Control realism: Model assumes adherence to protocol; deviations may affect outcomes
- Single-pathogen focus: Not designed for multi-pathogen coinfection scenarios
If you use MHASpread in your research, please cite:
Cespedes Cardenas, N., & Machado, G. (2024). Modeling foot-and-mouth disease dissemination in Brazil and evaluating the effectiveness of control measures. Frontiers in Veterinary Science, 11, 1468864. https://doi.org/10.3389/fvets.2024.1468864
This repository contains documentation and educational materials for MHASpread. The proprietary model source code is provided under a separate commercial or institutional license agreement. See LICENSE.md for details.
MHASpread development is supported by:
- FUNDESA RS (Fundação de Desenvolvimento para Excelência em Ciência e Tecnologia do Rio Grande do Sul)
- NC State University - Department of Population Health and Pathobiology
- LUMAC (Laboratório de Unidades Multidisciplinares de Apoio Científico) — Universidade Federal de Santa Maria
🖥️ Nicolas Cespedes Cardenas
Machado Lab, College of Veterinary Medicine
NC State University
🖥️ LUMAC Team
Universidade Federal de Santa Maria, Brazil
For detailed technical documentation, visit our comprehensive documentation site or explore the sections below:
- Model Overview — Detailed model structure and compartments
- Transmission Dynamics — Within-farm and spatial transmission mechanisms
- Control Strategies — Detailed description of interventions
- Economic Impact — Cost-effectiveness integration
- Data Requirements — Input data specifications and preparation
- Events & Training — International workshops and capacity-building
- Vignettes — Conceptual tutorials and use cases