Feral Swine and Foreign and Emerging Animal Diseases - Dr. Lindsey Holmstrom; Diagnostic Epidemiologist, Center for Foreign Animal and Zoonotic Center, from the 2013 NIAA Merging Values and Technology conference, April 15-17, 2013, Louisville, KY, USA.
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Dr. Lindsey Holmstrom - Feral Swine and Foreign and Emerging Animal Diseases
1. Feral Swine and Foreign and
Emerging Animal Diseases
NIAA Animal Health Emergency
Management Council
Dr. Lindsey Holmstrom
April 16, 2013
2. 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. 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
4. Purebred Eurasian (Left) v. Feral/Hybrid (Right)
Photos courtesy of Dr. Ed Stephens, Two Rivers Outdoor Club, Inc. 4
5. 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
6. 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
7. 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
8. 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
10. 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
11. 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.
12. 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
14. 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
15. 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
16. 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
17. 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
18. Factors influencing disease spread in feral swine
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
19. 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
19
20. 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
20
21. 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 21
22. 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 22
23. 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 23
24. Interplay of ecological and epidemiological
factors affecting disease spread in feral swine
Source: Kramer-Schadt et al. 2007
25. 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. 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
27. 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
28. CA wild pig project
3 study areas representing
different ecoregions
North Coast
Redwoods, oak
Central Coast
Oak, grasslands
San Joaquin Valley
Oak, grasslands, riparian
29. 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
30. 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
31. 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
36. 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
37. 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
38. 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
40. 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?
41. 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
42. 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