1. Diseases in Nature Conference
Focal Seroprevalence of Francisella tularensis in Feral Swine in North Central and Northwest Texas
Diseases in Nature Conference
Corpus Christi, Texas
16 June 2011
Steven M. Presley, Ph.D.
Endocrine Disruption
The Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas

2. Feral Swine: The Problem?
Introduced by DeSoto 1539 into Florida, spread(ing) west.*,** Feral swine reported in 38 states.*** Population is estimated at approximately 4-5 million in U.S., with million reported in 215 of 254 Texas counties.** Feral swine cause an estimated annual loss of ~$800 million nationwide, with ~$58 million in Texas
* Engeman et al. Environ. Conserv ; ** Higginbotham et al., Natl. Conf. Feral Hogs. 2008; *** Wyckoff et al. J. Wldlf. Dis

3. Expanding Range - 1988 Expanding Range - 2004
Adapted from: Texas Cooperative Extension May 2004 Report
Adapted from: SCWDS Feral/Wild Swine Populations 1988 Map

4. Projected Sow Population Increase
How many SOWS could one sow produce if she, each of her offspring, and each of their offspring produced average litters of 3, 5 or 6 gilts per year? (2 litters/year of 8-10 pigs)
46,656
78,125
59,049

5. Feral Swine: The Threat
Known reservoirs of pathogens including Salmonella spp. and E. coli. Serologic surveys detected enzootic feral swine infection with Brucella suis in 10 states (Arkansas, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, Missouri, South Carolina, and Texas). Study in 2006 found that in peanut butter contaminated with significant levels of Salmonella spp. prior to pasteurization, some viable Salmonella spp. could survive pasteurization

6. Ongoing Studies
Biological and ecological factors related to feral swine population explosion, geographic spread and threat to human and domestic animal health
Do feral swine harbor zoonoses in this region (Brucella spp., Francisella tularensis)?
Are feral swine involved in maintenance and transmission dynamics of zoonoses?
Is fenceline transmission to domestic livestock a possibility / threat?
Interaction with other wildlife populations?
Northern bobwhite
(Colinus virginianus)
Scaled “Blue” quail
(Callipepla squamata)

7. Tularemia
Highly infectious; very small infective dose (10-50 organisms); Category A biological threat agent; typically found in wild animals (enzootic cycle); Untreated CFR of 1-10%. Humans infected by bodily fluids/tissues, contaminated food or water, inhalation, or through the bite of infected arthropods (most commonly, ticks and deerflies). Presentation depends on the route of infection, including oropharyngeal (via ingestion), ulceroglandular and glandular (via direct contact or arthropod vectors), pleuropneumonic (via inhalation), and systemic forms. Typically about 200 human cases annually in the U.S.A., mainly in rural areas of south-central and western states.

8. Tularemia – infectious agent
Today – Four biovars / subspecies
Francisella tularensis tularensis (nearctica) (A)
Rabbits – North America
Francisella tularensis novicida (B)
Unknown – North America, Australia
Francisella tularensis holartica (palaearctica) (B)
Hares, rodents – Nearctic, Palearctic, Holarctic regions
Francisella tularensis mediasiatica (B)
Hares, rodents – Central Asia

9. PATHOGEN FINDINGS 72 serum samples from Bell & Coryell Counties
29 serum samples from Crosby County

10. Methods Slide serum agglutination assay
F. tularensis antigen (BD) [no longer available]
BD & Co. protocol and results guide (+2 agglutination considered positive)
Enzyme-linked immunosorbent assay (ELISA)
Rabbit anti-swine IgG
Absorbance read at 405 nm
Seropositives assayed by RT-PCR at BSL-3 facilities at Lubbock Hlth Dept / LRN.

11. Findings Francisella tularensis screening Crosby County 29 51.7% (15)
Agglutination assay
Real Time-PCR assay
Sample collection site
# Serum samples screened
Sero-positive for F. tularensis
# Sero-positive samples
F. tularensis genetic positive
Crosby County 29
51.7% (15) 13
21.5% (3)
Bell & Coryell Counties 72
20.8% (15) 15
6.7% (1)
Collaborators (USAMRIID) cultured the 3 RT-PCR-positive samples from Crosby County, and identified them as F. tularensis novicida.

12. Findings
Of surveyed pigs found serologically positive for tularemia:
Crosby Co.
Bell & Coryell Co.
Females
15%
64%
Males
85%
36%
Adults
77%
86%
Juveniles
23%
14%

13. Relevance Francisella tularensis in Feral Swine
Explosive population growth and geospatial range expansion increases occurrence of F.t. in ecosystem.
Could confound or mask early detection of covert introduction of F.t.
Increasing encroachment into suburban and urban areas as “walking vectors”, contaminating food crops, water sources and recreational areas.

14. Additional Findings Brucella spp. screening 3.7% (1) 4.3% (3)
Agglutination assay
Sample collection site
# Serum samples screened
Sero-positive for Brucella spp.
Crosby County 27
3.7% (1)
Bell & Coryell Counties 70
4.3% (3)

15. Summer / Fall 2011
Screen for Brucella spp., F. tularensis and Coxiella burnetti.
Comparative between High Plains (Hockley Co.) and Rolling Plains (Scurry Co.) ecoregions.
Screen environmental samples, including:
Mud/water from wallows;
Soil and vegetation from “nests”;
Ticks, deer flies and mosquitoes.

16. Thank You. Questions? Anna Hoffarth Dr. Brad Dabbert (TTU)
Acknowledgement:
Anna Hoffarth
Dr. Brad Dabbert (TTU)
Trish Jenkins (CLHD)
Thank You. Questions?

18. Distribution in U.S.A.

19. Brucella spp. Six recognized species: Relatively environmental stable
B. abortus – cattle & other bovids (humans)
B. canis – dogs (humans)
B. melitensis – sheep & goats (humans)
B. neotomae – wood rats
B. ovis – sheep
B. suis – swine (humans)
Relatively environmental stable
Humans typically exposed through inoculation, inhalation or ingestion.

20. Projected Total Population Increase
How many total feral hogs would those SOWS produce based upon their established pigs/year: 6 (3 pigs/litter x 2 litters/yr); 10 (5 pigs/litter x 2 litters/yr); or 12 (6 pigs/litter x 2 litters/yr)?
Average Litter Size
Years Since 1st Sow
Pigs Produced in Next Year
3 pigs 10
354,294
5 pigs 7
781,250
6 pigs 6
559,872