Dr. Lindsey Holmstrom - Feral Swine and Foreign and Emerging Animal Diseases

Feral Swine and Foreign and
Emerging Animal Diseases
NIAA Animal Health Emergency
Management Council
Dr. Lindsey Holmstrom
April 16, 2013

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
2

3
 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

Purebred Eurasian (Left) v. Feral/Hybrid (Right)
Photos courtesy of Dr. Ed Stephens, Two Rivers Outdoor Club, Inc. 4

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 Swine
Preexisting
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
 PRRS
Tularemia
 West Nile virus
 E. coli
 Salmonella
 Bovine Tuberculosis
 Influenza
 Streptococcus
 Ticks, Fleas, Lice
 Internal parasites
2

 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 8

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
10

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)
11
Ornithodoros sp.

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)
12

ASF: Geographic Distribution
13Source: 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

 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 – 2001
Source: Artois et al. 2002
16

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
17

1. 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
18

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
Photo courtesy of Fred Parker
19

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
20

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 21

5. Habitat connectivity
 Connectivity of populations across fragmented landscapes
 Interaction between social groups
 Population structure
 Overlapping home
ranges – where?
 Landscape barriers
Photo courtesy of Drs. H. Morgan Scott and Susan Cooper 22

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
Photos courtesy of Henry Coletto 23

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

26
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/Eurasian
boar
California Dept. of Fish & Game
27

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

 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?
30
Data Analyses

 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)
31
GPS data analyses

35
Wild pig GPS data: July-Oct 2011

36
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 site
Hog 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% less
8.89 km (7.893, 9.887)
5.97 (5.20, 6.74)
Central Coast
Boar (3)
Sounder (4)
58% less 45% less
7.77 km (6.45, 8.26)
4.53 (3.87, 5.28)
Texas
Boar (9)
Sounder (31)
65% less 43% less
6.45 km (5.44, 7.46)
4.43 km (3.71, 5.14)
1. Cowled et al. 2012
2. 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

39
Expected Outcomes
Adapted from Chetkiewicz et al. 2006

40
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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