Feral Swine and Foreign and Emerging Animal Diseases

NIAA Animal Health Emergency Management Council

Dr. Lindsey HolmstromApril 16, 2013

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Outline

U.S. Feral Swine: Current Knowledge

Foreign Animal Diseases

Factors associated with disease spread

California wild pig project: data collection efforts to address the risk of FAD spread

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Widespread distribution, populations continue to increase Recent movement/purposeful introductions in northern states Eurasian boar importation from Canada

Exotic, invasive species

Population estimates 4 to 5 million

Economic costs: ~ $800 million/year

SCWDS http://128.192.20.53/nfsms

U.S. Feral Swine Population

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Purebred Eurasian (Left) v. Feral/Hybrid (Right)

Photos courtesy of Dr. Ed Stephens, Two Rivers Outdoor Club, Inc.

Two Main Types of Wild Boar Hunting Preserves in U.S.

Free Range Wild Boar Hunting Preserves

Enclosed Area Wild Boar Hunting Preserves

Primarily Southern US Primarily Northern US

• Guided & unguided feral swine hunting

• More traditional hunting

• Guided hunting in an enclosed area

• Areas range from 80 to 1000s of acres

• Many operations have 500 – 1000 customers/year

• Prices normally are $500 - $700/hunt

Supply Channels for Wild Boar Hunting Preserves

Free Range Wild Boar Hunting

Preserves

Enclosed Area Wild Boar Hunting

Preserves

Feral SwinePreexisting Feral Swine Population

Trapped Feral Swine

from Southern

US

Raised Eurasian or

Hybrid Swine From Canada

Primarily Southern US Primarily Northern US

Known Feral Swine Diseases and Risks

Swine Brucellosis Pseudorabies Trichinosis Leptospirosis Toxoplasmosis Classical Swine Fever African Swine Fever Foot and Mouth Disease Anthrax Hepatitis E

PRRSTularemia West Nile virus E. coli Salmonella Bovine Tuberculosis Influenza Streptococcus Ticks, Fleas, Lice Internal parasites

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Infects cloven hooved animals African buffaloes maintenance hosts

Last outbreak in the US: 1929

22,214 deer killed in CA outbreak, 1925

Unexpected for feral swine to be reservoirs but could play a role in limited disease spread

Foot and mouth disease (FMD)

Photo courtesy of California Dept. of Fish and Game

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Bulgaria 2011 outbreaks and role of wild boar

No virus was isolated from wildlife except for the index case

Introduction of FMDV by wildlife is less likely than introduction due to movement of domestic animals or animal products

FMD will not be sustainable within a wild boar and deer host system alone but limited spread of FMDV in time and space may occur Continued cross-over of FMDV between domestic and wildlife

population may prolong virus circulation Wildlife population is not able to maintain FMD in the

absence of FMDV infection in the domestic host population

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African Swine Fever (ASF)

Infects domestic/wild swine European wild boar get sick, African wild swine do not

Probably a tick virus with pigs as accidental hosts Competent Vectors in US

O. coriaceus: Pacific coast Calif. & Mexico O. turicata: Southern U.S. up to Kansas

Direct and indirect transmission Acute and chronic disease forms

Recovered pigs may be carriers for life (up to 25% estimated in Russia)

Ornithodoros sp.

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African Swine Fever (ASF)

Up to 100% morbidity Mortality varies with virulence (0-100%)

Virus usually disappears from wild boar when disease is controlled in domestic swine Lower virulent strains are emerging Can be very difficult to diagnose

Historically present in Sub-Saharan Africa & Sardinia Virus escaped Africa via pork products Spread in 2007 to the Caucasus and then Russia Serious threat to Europe (wild boar & smuggled pork)

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ASF: Geographic Distribution

Source: World Animal Health Information Database (WAHID), OIE

Classical Swine Fever (CSF)

Highly contagious, economically costly viral disease of swine; Hog Cholera

Natural Hosts: pig and wild boar Enveloped RNA virus, one serotype

family Flaviviridae, genus Pestivirus Bovine Viral Diarrhea Virus (BVD)

U.S. declared CSF free in 1978 after a 16 year eradication campaign

Cost $140 million (est. cost over $525 million today) Assumed disease not maintained in feral/wild pigs

CSF: Continual Risk of Introduction

Worldwide distribution

Ease of access to the virus

Currently circulating viral strains are predominately low/moderately virulent, may delay detection

Source: World Animal Health Information Database (WAHID), OIE

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Outbreaks not necessarily self- limiting

CSF endemic in some wild boar populations

Germany: 1990-98, ~59% of outbreaks due to direct/indirect contact with infected wild boars

Economic costs due to control measures ~US $1.5 billion

Italy – Illegal to hunt

CSF in Wild Boar

CSF outbreaks in wild boar, 1990 – 2001Source: Artois et al. 2002

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Factors influencing disease spread in feral swine

1. Population distribution and density

2. Social and spatial structure

3. Movements

4. Habitat connectivity

5. Inter-species contact

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Factors influencing disease spread in feral swine1. Population distribution/density

Distributions continue to increase in the US Natural dispersal from existent populations Release or escape of domestic swine that then become feral Escape from hunting preserves or confinement operations European wild boar importation Purposeful translocation and release by humans for sport hunting

Feral swine are extremely adaptable Reliable and adequate food and water supply and vegetation cover Opportunistic omnivores, lack of predators Densities higher in resource-rich areas Human environment change has made habitat more favorable for feral swine

Behaviorally adaptive, difficult (impossible) to eradicate

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2. Social and spatial structure Form social groups called

sounders Consist of two or more sows

and their young Majority younger pigs

Adult boars are usually solitary

Territorial Interaction during breeding, at common water/food sources

Usually nocturnal, seldom move during the day

Factors influencing disease spread in feral swine

Photo courtesy of Fred Parker

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3. Population dynamics Highest reproductive capacity of all large, free-ranging mammals

1-2 litters of 4–8 piglets per year Populations can double in 4 months 70% of population would need to be killed to keep current status quo

Populations are resource driven

Survival of piglets dependent on rainfall, food availability and predation rates

In good years, populations rapidly recover to large numbers after high mortality

Factors influencing disease spread in feral swine

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Factors influencing disease spread in feral swine

4. Movements Sedentary within their home range

Home range typically 3-5 square miles, up to 20 square miles Sex, age, habitat, food availability, and temperature

Movement is not random across the landscape

GPS data courtesy of Drs. H. Morgan Scott and Susan Cooper

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5. Habitat connectivity Connectivity of populations across fragmented landscapes

Interaction between social groups

Population structure

Overlapping home ranges – where?

Landscape barriers

Factors influencing disease spread in feral swine

Photo courtesy of Drs. H. Morgan Scott and Susan Cooper

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6. Intra- and inter-species contact Feral swine are sympatric with outdoor domestic livestock and other

wildlife species Predation on calves, lambs, goat kids, exotic game

Factors influencing disease spread in feral swine

Photos courtesy of Henry Coletto

Interplay of ecological and epidemiological factors affecting disease spread in feral swine

Source: Kramer-Schadt et al. 2007

The Problem GAO (2009): “If wildlife became infected [with a foreign animal disease]…

response would be greatly complicated and could require more veterinarians and different expertise.”

US response plans Assess the risk wildlife present and

strategies to prevent domestic/wildlife interaction – how?

What we do not know: Fade-out or become endemic? Time to detection? Potential domestic/wild pig interaction? Control and mitigation strategies?

Lack of data to develop a wildlife epidemic model with confidence

Photo courtesy of Henry Coletto

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CA Wild Pig Project: The Approach

Collect empirical data on California wild pigs Global positioning systems (GPS) Geographic information systems (GIS) Landscape genetics

Data collection and analyses based on factors important to disease spread: Habitat, movements, contacts, population

connectivity

Wild Pigs in California Estimated population varies

from 200,000-1 million

Non-native, invasive species

Year-round hunting, no bag limit

Hybrid: feral swine/Eurasianboar

California Dept. of Fish & Game

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CA wild pig project

3 study areas representing different ecoregions

North Coast Redwoods, oak

Central Coast Oak, grasslands

San Joaquin Valley Oak, grasslands, riparian

The Data Sampling sounders and boars Locations monitored

Collar stays on pigs for 10 wks GPS locations every 15 min

(7pm-7am); every 1 hr (7am-7pm) Blood samples – USDA:APHIS WS

ASF, FMD, CSF, influenza, PRV, brucellosis, trichinella, tularemia, Hepatitis E, E. coli, toxoplasmosis

Genetic samples Hair, tissues, blood

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Movement patterns How do pigs move through different habitat

types?

Factors associated with habitat selection

Where do pigs spend their time?

Habitat connectivity What is the spatial extent of contact between

(sub)populations?

Data Analyses

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Analyses focus on parameters used in current wildlife disease models

Movement parameters Day/night, daily, weekly, monthly movements; hog type Environmental and seasonal assessments

Probability of contact between social groups (herds of wild pigs)

GPS data analyses

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Mendocino County, CA

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August 12, 2011

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August 17, 2011

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Wild pig GPS data: July-Oct 2011

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Data analyses

Longitudinal analyses; seasonality will be assessed after all data collected

Current feral swine disease model parameters: Random movement of wild pigs within circular home ranges; 1km

daily movement distance1-3

Mobility models sensitive to daily herd movement distances1-2

Study siteHog type (number)

Distance traveled during the day

Distance traveled in preferred habitat

Distance traveled per day (CI)

North Coast

Boar (9)

Sounder (8)

54% less 49% less8.89 km (7.893, 9.887)

5.97 (5.20, 6.74)

Central Coast

Boar (3)

Sounder (4)

58% less 45% less7.77 km (6.45, 8.26)

4.53 (3.87, 5.28)

Texas

Boar (9)

Sounder (31)

65% less 43% less6.45 km (5.44, 7.46)

4.43 km (3.71, 5.14)

1. Cowled et al. 20122. Kramer-Schadt et al. 2009 3. Milne et al. 2008

Aim: To assess the association between landscape pattern and habitat selection

Adapted from Chetkiewicz et al. 2006

Data Analyses:(2) Factors associated with habitat selection

Population connectivity

Landscape genetics = population genetics + landscape ecology + spatial statistics

Characterizes areas between habitats and their influence on biological/ecological processes (connectivity) Landscape metrics Gene flow/relatedness Effective population size Barriers to gene flow

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Expected Outcomes

Adapted from Chetkiewicz et al. 2006

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Implications for foreign animal diseases

Understanding potential FAD spread requires knowledge of wild pig distribution Habitat selection

Understanding movements and potential contact Spatial extent/velocity of disease spread

Identifying areas of increased disease spread Where to look?

Implications for disease control Identifying areas to focus mitigation strategies

Disconnect subpopulations of wild pigs?

Future directions: Data generalizations Wildlife epidemic model Domestic/wildlife interaction Disease control strategies

Photo courtesy of Henry Coletto

Acknowledgements

Supported by the Foreign Animal Disease Modeling Program of the U. S. Department of Homeland Security Science & Technology Directorate

Drs. Pam Hullinger, Tim Carpenter, Este Geraghty (UC Davis), Morgan Scott (Kansas State Univ.)

Collaborators USDA/APHIS Wildlife Services – Shannon Chandler CA Dept. of Fish & Game – Ben Gonzales, Marc Kenyon Dick Seever, Rural Pig Management, CA Private land owners, CA

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Questions?