identifying and optimizing prevention and control strategies … · 2017-03-05 · factors...

Identifying and optimizing prevention and control strategies against the spread of viral pathogens within U.S. feral swine populations

Dr. Lindsey Holmstrom October 20, 2013

Project HSHQDC-10-C-00116

Overview

Review of current knowledge of U.S. feral swine CA Wild Pig Project GPS data Field data collection Data analyses

Conceptual model

Future directions

Sargent (2008) 2

Widespread distribution, populations continue to increase Recent migrations/purposeful introductions in northern states Eurasian boar importation from Canada Population estimates range from 4 to 5 million Economic costs: ~ $1.5 billion/year FAD spread?

SCWDS http://128.192.20.53/nfsms

U.S. Feral Swine Population

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Factors influencing disease spread in feral swine

1. Population distribution and density

2. Social and spatial structure

3. Population dynamics

4. Movements

5. Habitat connectivity

6. Inter-species contact

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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 Densities higher in resource-rich areas Human environment change has made habitat more favorable for feral swine

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

Photo courtesy of Fred Parker, 2011 6


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

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

mortality

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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

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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

Photo courtesy of Drs. H. Morgan Scott and Susan Cooper 9


6. 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 10

Exotic Transboundary Diseases

Foot and mouth disease (FMD) African buffaloes maintenance hosts 22,214 deer killed in CA outbreak, 1925 Unexpected for feral swine to be reservoirs but could play an important role in disease spread Bulgaria 2011 outbreaks and role of wild boar

African swine fever (ASF) Infects domestic/wild suids, Up to 100% morbidity and mortality Acute and chronic disease forms Virus usually disappears from wild boar when disease is controlled in domestic swine Milder viral strains are emerging

Photo courtesy of California Dept. of Fish and Game

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Exotic Transboundary Diseases

Classical swine fever (CSF) 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 UK 2000: ham sandwich? CSF outbreaks in wild boar, 1990 – 2001

Source: Artois et al. 2002

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

Source: Kramer-Schadt et al. 2007 13

The Problem GAO (2009): “If wildlife became infected [with an exotic transboundary

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 on factors affecting disease spread in feral swine populations

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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)

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

connectivity

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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

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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

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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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Data collection: March 2010 – October 2012

GPS collars placed on 59 pigs at 8 different study sites Finished GPS collar retrieval (Dec 2012)

San Diego County trapping

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Wildlife data collection process Feral swine dataset we are collecting will be the largest in

the US Modeling, FAD policy, surveillance purposes Continued interest in analyses/findings

Process of collecting good/useful feral swine data

Time Dependent on weather, season/ food availability, human disturbance (e.g. hunting, logging), “pig knowledge”, trap placement

Relevance for FAD response plans

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GPS Data Analyses

1. Movement patterns How do pigs move through different habitat

types?

2. Factors associated with habitat selection Where do pigs spend their time?

3. Habitat connectivity What is the spatial extent of contact between

(sub)populations?

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GPS 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) 22

1. Movement Patterns

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 (13)

52% less

47% less

8.76 km (7.652, 9.998)

5.84 (5.11, 6.85)

Central Coast Boar (11)

Sounder (11)

58% less

45% less

7.77 km (6.45, 8.26)

4.53 (3.87, 5.28)

San Joaquin Valley

Boar (6)

Sounder (10)

55% less

44% less

6.87 km (5.44, 8.34)

5.45 km (3.71, 6.57)

1. Cowled et al. 2012 2. Kramer-Schadt et al. 2009 3. Milne et al. 2008

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2. Factors affecting habitat selection

Knowledge of general and local distribution needed (i.e. where are pigs?) Currently this is done using expert opinion, hunting

or anecdotal information due to resource constraints

Relationships between habitat selection and landscape pattern affect distribution Habitat selection as a proxy for distribution Where do pigs spend their time?

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Study design: longitudinal, spatial Spatial extent:

100% Minimum Convex Polygon Resolution (pixel): 500x500 meters Unit of analysis: landscape unit Outcome:

time spent in landscape unit Explanatory variables:

Habitat (% cover, distance to water, cover/food, NDVI, etc.) Temperature, precipitation Road density Month (season), time of day, study site

Offset: area of useable land

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Identify the habitat connectivity/contact of feral swine populations and assess disease spread control options

Can landscape features be exploited to

disconnect feral swine populations across the landscape?

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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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Defining spatial relatedness in wildlife

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Defining spatial relatedness: minimum convex polygon

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Home range overlap (~contact for disease spread)

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Defining spatial relatedness: kernel density

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Defining spatial relatedness: directional distribution

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Data analyses

Current feral swine disease model parameters: Contact usually occurs (e.g. 0.75 probability1) at locations where home ranges overlap1-4 Models sensitive to probability of disease transmission1-2,4

Study site Contact type Percent home range

overlap Percent of locations within overlapping home range

North Coast

Boar to Boar

Boar to Sounder

Sounder to Sounder

4.593%

10.887%

14.438%

1.047%

4.673%

23.453%

Central Coast

Boar to Boar

Boar to Sounder

Sounder to Sounder

6.345%

14.342%

21.434%

3.234%

7.790%

24.627%

San Joaquin Valley

Boar to Boar

Boar to Sounder

Sounder to Sounder

5.25%

11.551%

21.690%

4.554%

8.501%

20.255%

1. Cowled et al. 2012 2. Laffan et al. 2011 3. Kramer-Schadt et al. 2009 4. Milne et al. 2008

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Conceptual Model

Base conceptual model for viral pathogens in feral swine populations

Increase complexity based on type of pathogen

FMD, CSF, PRV

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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? 39

Future Directions

Wildlife disease model

Livestock/wildlife interface

Disease Control Strategies

Wildlife database

Continued data analysis Comparisons with Texas feral swine dataset New Mexico GPS data collection Landscape genetics analyses

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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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identifying and optimizing prevention and control strategies … · 2017-03-05 · factors...

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