Modeling Emerging Disease in the U.S. Swine Herd

Shweta BansalAssistant Professor of Biology, Georgetown University

Faculty Fellow, National Institutes of Health

U.S. Agricultural Disease Preparedness

“New, emerging, and evolving pathogens are a challenge to animal health and production. Although improved management and better diagnostic and prophylactic tools are now available, emerging diseases and changes in animal management will always create new opportunities for old diseases.”

“Successfully overcoming these challenges requires a U.S. agricultural research enterprise that harnesses the newest advances from across the physical and life sciences, builds on a broader public investment in science and technology, and then applies these discoveries to the specific challenges of agriculture.”

U.S. Livestock Diseases

Mole, Nature (2013)

Current outbreak: PEDV Potential threat: FMD

Zoonotic impact: Influenza

U.S. Swine Industry

The U.S. swine industry is highly connected and intensely aggregated

U.S. Swine MovementShields & Mathews, USDA (2002)

U.S. swine production density (USDA Agricultural Census)

Linking Disease to Livestock

Movement

Increased livestock movement Increased prevalence of bTB

Gilbert et al, Nature (2005) Shirley & Rushton, Epidemiology and Infection (2005)

High animal throughputs High risk of infection

Role of Disease Modeling

During Epidemic Assess means of spread

Predict future spread

Design control

Endemic Stage Disease Management

Prior to Emergence Surveillance

Preparedness

RISK

ANALYSIS

DETERMINE

TRANSMISSION PATHWAYS

CONTAIN SPREAD

PEDV Transmission Pathways

PEDV Spread in U.S.

Data: USDA/AASV; O’Dea et al (2014)

Open Questions About PEDV

Is swine movement responsible for propagating the infection?

What other factors increase risk of infection?

What was the source of the infection in the U.S.?

Important for surveillance, control and preparedness

Role of Swine Movement in PEDV

Is swine movement responsible for propagating the infection?

Evidence of spread by trailers found (Lowe et al, 2014)

Many states have responded by limiting imports from PEDV-free premises

However, mode of transmission remains open to speculation

Role of Movement in PEDV Spread

O’Dea, Snelson, Bansal (2015, In Review)

What is the impact of movement direction?

Evidence for trailer-based transmission

Source of Infection

What was the source of the infection in the U.S.?

First cases detected in OH and IN but entry unknown

Source of PEDV in US

Do arrival times of PEDV in different states provide information on origin?

Arrival times of PEDV

Dec 2013April 2013

Estimation of Likely Disease Source

Input: probability of disease spread between areas, genetic data, time of disease detection, model of detection error

Output: approximate likelihood of each state as source

Source: IN

Source:

KS

Distribution of arrival times from IN OH

Controlling an Outbreak

Movement Restrictions to Control PEDV

Self-imposed restrictions

Optimized restrictions

Regionalization as a Tool for Livestock

Disease Control

Complex network community structure analysis

Large-Scale U.S. Regionalization

Density-dependent transmission

Frequency-dependent transmission

Feasibility of Regionalization

Optimized for feasibility and efficiency1) Spatial cohesiveness2) Spatial contiguity

Assessing Risk of Emergence

Quantifying Risks for Swine Disease Emergence

Swine density Live swine movement

+

+

Importation of swine

+

Shipment of pork + animal

feed

Quantifying Risks for Swine Disease Emergence

Network-based model of risk for swine disease

emergence

Identification of hotspots for introduction and spread

Summary

Network modeling swine industry connectivity

PEDV: identification of disease transmission pathways and sources

Crucial for identifying biosecurity gaps and preventing future introductions

Design of control strategies for containing spread

Optimal strategies adapted for feasibility and business continuity

Risk analysis for swine disease emergence

Improved biosurveillance and preparedness

Increased access to global trading partners

Acknowledgements

GroupEamon O’Dea

Ian Carroll

Madeline Campbell

Collaborators:

Harry Snelson (AASV)Ryan Miller (USDA APHIS)Jason Lombard (USDA APHIS)Katie Portacci (USDA APHIS)Colleen Webb (CSU/RAPIDD)Michael Buhnerkempe (UCLA/RAPIDD)James Wood (Cambridge)John Korslund (USDA APHIS)Laura Pomeroy (OSU) Bryan Grenfell (Princeton)

Support: Department of Homeland Security Foreign Animal

Disease Modeling Program

RAPIDD Program of the Science & Technology Directorate of the DHS and the Fogarty International Center, National Institutes of Health.

Images from Wikimedia Commons. Michigan Farm Bureau, USDA, BBC News

Modeling Emerging Disease in the U.S. Swine Herd

Shweta Bansal

Web: http://bansallab.com

Twitter: @bansallab