Disease Threats Endemic in Wildlife Populations that Pose Threats to U.S. Livestock and Our Export Markets

Ray Waters, DVM, PhDTuberculosis Research Project

National Animal Disease CenterAmes, Iowa

Emerging Diseases of Wildlife

Wildlife

Domestic Animals

Humans

Feeding

Habitat destruction

Translocation of wildlife

Encroachment

Introduction

Spill-over and spill-back

Daszak, P. et al., Science 2000;287:443-449

Impact on Federal Eradication Programs• Bovine Tuberculosis (TB) in White-Tailed Deer (MI, MN, IN)

• Brucellosis in Elk, Bison, (Yellowstone, B. abortus) & Feral Swine (B. suis)

• Pseudorabies (PRV) in Feral Swine

Others

• Johne’s Disease in White-tailed Deer

• Bovine Viral Diarrhea Virus (BVDV) in White-tailed Deer

• PRRSV, SIV, PCV-2, Leptospira (~50% prevalence & may harbor serovarsnot covered by current bacterins used for cattle), CWD? in feral swine

• Potential Host for Foreign Animal Diseases

So, where did these diseases come from?

And cattle & pigs w/ hitchhikers: (e.g., Mycobacterium bovis, Brucella spp, PRV, Johne’s, and BVDV)

Circa 1500 A.D.: Horses are introduced to America

Encroachment, Introduction, Feeding, Spill-Over and Spill-BackGame Management:

Increased carrying capacity

Interaction w/ our Livestock

Expanding Range

lib.colostate.edu

Feeding / Baiting Practices

Contamination of FeedFeeding,

Encroachment, Spill Back

Expanding Range!!!

Expanding Range and Natural Interactions w/ ‘Transitional Production Swine’

Natural Interactions w/ Cattle in Pastures

PRV in Feral Swine• 1991: USAHA, Feral Swine Subcommittee: Feral swine

recognized as a significant threat to PRV and Brucellosis eradication.

• Low virulence strains w/ delayed seroconversion can result in spread w/o detection when transmitted to domestic pigs

• Out of 2,849 sera samples (2009 – 2012), 18% seropositive for PRV in 25 of 35 states (Pederson et al, 2013)

• While all states achieved PRV-free status in 2004; feral swine remain as a reservoir of PRV and a threat to ‘transitional’ operations

Brucellosis in Feral Swine• B. suis: risk for ‘transitional’ swine operations; thereby

hindering eradication efforts

• B. suis in pigs: poor accuracy of serologic tests, bacteremia of longer duration than B. abortus, and B. suis is frequently shed in urine

• B. suis can infect cattle and shed at high levels in milk (demonstrated risk w/ unpasteurized dairy products)

• B. suis infection in humans (e.g., hunters, trappers): often severe disease and may relapse

Bovine TB• Primarily due to Mycobacterium bovis

• Wildlife reservoir hosts

• US eradication program initiated in 1917

• Current issues (US): tuberculous cattle from Mexico, occasional inter-herd spread, WTD in MI, & captive cervids

• 2000 – present: 144 TB-affected herds:

MI (51 beef, 15 dairy, 4 cervid, 1 dairy), MN (12 beef), TX (7 dairy, 3 beef, 1 mixed), CA (11 dairy), CO (5 beef, 2 dairy), IN (3 beef, 3 cervid), NM (4 dairy, 1 mixed), SD (4 beef)

AZ, KS, KY, MS, NE, NY, ND, OH, OK, & OR (all < 3)

www.bavarianbirds.de

www.raysweb.net

www.fortunecity.comPulsar.Two-worlds.com

from U. of Missouri Extension publication

Example of Human Impact on Wildlife Populations

Deer densities > 30/sq. mile - SCWDS 198250/sq. mile – MI DNR 1990

The Tale of Michigan

1922-1928 Bovine TB ReactorRates in Michigan’s Cattle Herd

77/1550

Berrien Cass St. JosephBranchHillsdaleLenawee Monroe

WayneWashtenawJacksonCalhounKalamazooVan Buren

Allegan Barry Eaton InghamLivingstonOaklandMacomb

St. ClairLapeerGenesee

Sanilac

Huron

Tuscola

ShiawasseeClinton

Saginaw

Bay

IoniaKent

Ottawa

MontcalmGratiot

MidlandIsabellaMecostaNewaygo

Muskegon

Oceana

Mason Lake Osceola Clare GladwinArenac

IoscoOgemawRoscommonMissaukeeWexfordManistee

BenzieGrand TraverseKalkaskaCrawfordOscoda Alcona

MontmorencyAlpenaOtsegoAntrim

Leelanau

CharlevoixPresque Isle

CheboyganEmmet

Mackinac

Chippewa

Luce

SchoolcraftDelta

Alger

Menominee

Marquette

Dickinson

Iron

Gogebic

Ontonagon Baraga

Hou`ghton

Keweenaw

211/5618 251/5318 92/2056

0/959``

179/4551176/293175/2529

98/206884/2431618/2691159/1106

68/157376/304755/1410233/4845

1567/14518353/28021556/32448

50/1532213/2597161/633630/85248/1931294/2741

450/14100

236/3536357/5298

578/29386

12/197 254/3686

133/647527/55243/645

5/68

7/1201

120/2008

181/3223 54/857

2/761/24667/253229/528

7/4322/209211/561816/3652/497/469

10/287 4/383 160/2101

38/2513

28/1382/130227/662020/20122/103

16/104 32/2185 166/6222 98/2049 1/17 31/97

24/6523/95

10/268

16/1741

144/1435

69/3413

25/2494

2/109

1/118

1/89

32/2497

16/123

3/67

136/4877

5/202

54/2410

30/2655

1/64

3/64

0% Reactors

0%-2% Reactors

2%-5% Reactors

5%-10% Reactors

10% or more Reactors

Spill-Over to Deer

Spill-Over to Deer

43

Spill-Back to Cattle!

Why does TB persist in deer in Michigan?

Supplemental Feeding and Baiting

• High deer numbers• Decreased winter death loss• Crowding & Stress• Contaminated feed• Increased risk of disease transmission• Indirect transmission through contaminated feed (deer to deer and deer to cattle)• Supplemental feeding drastically increased by hunt clubs in the core area – 1980s & 90s

• Prevalence decreased from 5% to 2% in the TB Core Area w/ increased hunter harvest as well as decreased baiting & supplemental feeding; yet transmission to cattle persists

• Since 2000: TB Prevalence in WTD persists at ~1.5 – 2.5%

• Could these efforts be more aggressive? Other Strategies (e.g., vaccines for deer)?

• Political Will Rights of Hunters vs Rights of Cattleman

Mitigation Actions beginning in 1996

• In 2015, 654,579 licensed hunters harvested ~334,612 deer statewide

• These hunters purchased 1.27 million harvest tags

• Opening day ( Nov 15) is a holiday for most schools in Northern Michigan

• Hunting is deeply ingrained in the culture in the TB core region w/ many hunt clubs

Culture of WTD hunting in Michigan

WTD hunting in Michigan:Economic value and political clout

• Big game hunters’ (mostly WTD) expenditures in MI: ~$1.4 billion yearly

• Hunting-related taxes generate another $24.2 million yearly for wildlife conservation

• By comparison, total market value of cattle and calves sold: ~$604 million yearly for MI

• TB Core Area: accounts for only 2% of cattle and dairy product sales in MI

• “Persistent and intense public intolerance of drastic reductions in the deer population has proven more influential than protests by cattlemen and their advocates”, O’Brien et al., 2006

U.S. Dept. Interior, 2011; U.S. Dept. Agriculture, 2012

Disease Management in Wildlife: Surveillance, Population Control, Exclusion, Vaccination

Exclusion: Use of Guard Dogs

Exclusion: Fences around Feed Storage Areas

1. Gonacon: Licensed for WTD and feral horses

2. Zonastat-P, Zonastat-D, Zonastat-H

3. One Hit Permanent Sterility (cytotoxins to oocytes as chemosterilants): 1st target is feral pigs

4. Genetic Biocontrol w/ Natural or Synthetic Gene Drives: 1st target is invasive rodents on islands

NWRC: Led by Doug Eckery in collaboration w/ CSU

Vaccine Efficacy Studies (bovine TB) in White-tailed Deer

BCG for Bovine TB: White-tailed Deer• BCG Danish and Pasteur provide similar levels of

protection

• Oral administration provides similar to superior efficacy as does subcutaneous

• BCG is detectable within lymph nodes (not tissues normally consumed by hunters) 9 to 12 months after vaccination and may transmit between deer

Camille Guerin

Albert Calmette

Vaccines, free-ranging deer“Without a vaccine it will be very difficult, maybe impossible, to eradicate TB in deer in Michigan” S. Schmitt, Michigan DNR

Trap, test and cull or vaccinate strategy

Baits for BCG Delivery

• Vaccine Uptake (NADC – captive deer, MI – free-ranging deer)

• Bait / Vaccine Viability

• Bait Dispersal Strategies

• Efficacy / safety of 100X dose

Vaccine delivery units (VDUs: alfalfa/molasses-based, corn-based, apple-based) for BCG in White-tailed Deer in MI

Vaccine Delivery Unit Dispersal Techniques

Drones

Game cameras to monitor bait uptake

Rhodamine B-laced baits to assess coverage (70%)

Many images and supportive data provided by:• Kurt Vercauteran & Chris Ellis, APHIS, WS

• Dan O’Brien, MI DNR

• Bill Hench, USDA, APHIS, VS, TB program staff

• David Dressel, MSU

• NADC:

Mitch Palmer/Tyler Thacker (TB), Steve Olsen (Brucella), Kelly Lager (PRV), Jarlath Nally (Lepto), Jim Fosse (Visual Services)

Kavango-Zambezi Transfrontier Conservation Areain southern Africa

Courtesy of Michele Miller, Stellenbosch Univ.

Minnesota vs. MichiganMinnesota Michigan

Size of bTB core area 425 km2 1480 km2

Topography/land cover Flat; mixed forest (25%), lowland marsh (35%), open agricultural (40%)

Flat to rolling; mixed forest (50%), lowland swamp (15%), open agricultural (30%)

Core area land ownership 60% public40% private

10% public90% private

Number cattle producers in core area

67 87

Free-ranging deer density 2-3 per km2 16-18 per km2

Annual expenditures by big game hunters

US$259 million US$1.4 billion

US rank, total agricultural products sold

5th of 50 18th of 50

US rank, value of cattle and calves sold

12th of 50 27th of 50

• 1813: Dr. Hildreth, a physician in Marietta Ohio notes a case of ‘mad itch’ in one of his client’s cows – 1st account in the US of what was later to be known as PRV

• 1902: Hungarian Veterinarian Aladar Aujeszky 1st recognizes Pseudorabies as a fatal disease in a bull, cat and dog. About this time, it was determined that pigs are the reservoir host

• Assumption – PRV arrived in the new world from European domestic pigs

Photo by George W. Beran

• Mycobacterium tuberculosis complex DNA isolated from an extinct long horned bison metacarpal bone (dated at ~17,870 yrs) in Wyoming

• Not M. bovis

• M. bovis likely diverged from M. tuberculosis ~5000 yrs ago

• Assumption: the vast majority, if not all, of M. bovis strains arrived in the New World with the settlers