Potential role of wildlife in the USA in the event of a foot-and-mouth disease virus incursion

Foot-and-mouth disease (FMD) is caused by foot-and-mouth disease virus (FMDV) which affects domestic and wild cloven-hoofed species. The FMD-free status of the USA and the tremendous economic impact of a virus incursion motivated the development of this evaluation of the potential role of wildlife in the event of a virus introduction. Additionally, this manuscript contains a summary of US vulnerabilities for viral incursion and persistence which focuses specifically on the possible role of wildlife. The legal movement of susceptible live animals, animal products, by-products and animal feed containing animal products pose a risk of virus introduction and spread. Additionally, the illegal movement of FMD-susceptible animals and their products and an act of bioterrorism present additional routes where FMDV could be introduced to the USA. Therefore, robust surveillance and rapid diagnostics in the face of a possible introduction are essential for detecting and controlling FMD as quickly as possible. Wildlife species and feral pigs present an added complexity in the case of FMDV introduction as they are typically not closely monitored or managed and there are significant logistical concerns pertaining to disease surveillance and control in these populations. Recommendations highlight the need to address existing knowledge gaps relative to the potential role of wildlife in FMDV introduction events

Feral Swine Disease Surveillance – National Targets and Pilot Projects

The National Feral Swine Damage Management Program (NFSP) in collaboration with the National Wildlife Disease Program (NWDP) and USDA APHIS Veterinary Services works to identify the diseases of national concern in feral swine. The current national disease surveillance program includes classical swine fever (CSF), swine brucellosis (SB), and pseudorabies (PRV). CSF is a foreign animal disease and feral swine samples collected and tested serve as part of Veterinary Services surveillance stream for this pathogen. Both SB and PRV have been eradicated from U.S. commercial swine operations; however, as they are endemic diseases in feral swine populations, monitoring of feral swine for SB and PRV is deemed important to inform the swine industry as well as other livestock entities of the potential risk of reintroduction. Wildlife Services routinely removes feral swine and collects serum (approximately 2,800 samples annually) to conduct serologic tests on these three diseases. Sampling is distributed over both space and time and is currently undertaken in 37 states of the U.S. with counties being ranked high, medium, and low priority based upon risk factors. In addition to the diseases of national concern, the NFSP supports a number of pilot projects to address disease issues that arise at a local level. In close collaboration with Wildlife Services field personnel and others on the ground, the NFSP is able to quickly and robustly identify and sample for additional pathogens of zoonotic, domestic livestock, or companion animal concern. These projects are often multi-agency collaborative efforts and include diseases such as bovine tuberculosis and chronic wasting disease

African Swine Fever

At the time of writing this chapter, a global pandemic of African swine fever (ASF) is ongoing with the virus having moved from Eastern Europe, Asia, and into the Caribbean—leaving swine production in devastation along the way. Due to the global spread of African swine fever virus (ASFV), the persistence of the virus, and the increasing number of endemic countries, this disease poses an imminent threat of introduction into North America and other countries that are currently ASF free. Throughout the chapter, we reference Eurasian wild boar (Sus scrofa) which are charismatic megafauna that are native to Europe and Asia. Wild boar were introduced into numerous areas in the southeastern United States and California by early settlers and they subsequently augmented and hybridized with established feral domestic swine (Sus scrofa) to give rise to contemporary populations of feral swine, a highly invasive species that are present across much of the United States. Feral swine are referred to by various terms, including wild hogs, feral pigs, wild boar, wild swine, razorbacks, and other regional names in North America. African swine fever has never been introduced into the United States; as such, we do not discuss feral swine in specific within the chapter. However, experimental inoculations demonstrate that feral swine are acutely susceptible to ASFV and given its current rapid global movement we anticipate similar patterns of exposure, infection, and risk amongst these populations

The National Feral Swine Program, National Strategy – The First Five Years

In 2014, through Congressional direction, the Animal Plant Health Inspection Service (APHIS) National Feral Swine Damage Management Program was created. While feral swine damage management was certainly not new to APHIS Wildlife Services, this mandate enabled a programmatic and unified approach in combating the destructive forces of feral swine throughout the United States and its territories. Recognizing the variance in environmental conditions and regulatory processes throughout the states, APHIS’ strategy is to provide resources and expertise at a national level, while allowing flexibility to manage operational activities from a local or state perspective. Having completed the first five years of this pursuit, APHIS has compiled a report which serves to describe the program and its components, ongoing collaborative research, the operational approach, and the outreach and communication campaigns. This presentation provided an overview of this report, introducing accomplishments achieved, setbacks encountered, and future considerations. The report will be electronically available on the USDA/APHIS/Wildlife Services web page at: https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamag

Feral Swine as Indirect Indicators of Environmental Anthrax Contamination and Potential Mechanical Vectors of Infectious Spores

U.S. government wor

Optimising response to an introduction of African swine fever in wild pigs

African swine fever virus (ASFv) is a virulent pathogen that threatens domestic swine industries globally and persists in wild boar populations in some countries. Persistence in wild boar can challenge elimination and prevent disease-free status, making it necessary to address wild swine in proactive response plans. In the United States, invasive wild pigs are abundant and found across a wide range of ecological conditions that could drive different epidemiological dynamics among populations. Information on the size of the control areas required to rapidly eliminate the ASFv in wild pigs and how this area should change with management constraints and local ecology is needed to optimize response planning. We developed a spatially explicit disease transmission model contrasting wild pig movement and contact ecology in two ecosystems in Southeastern United States. We simulated ASFv spread and determined the optimal response area (reported as the radius of a circle) for eliminating ASFv rapidly over a range of detection times (when ASFv was detected relative to the true date of introduction), culling capacities (proportion of wild pigs in the culling zone removed weekly) and wild pig densities. Large radii for response areas (14 km) were needed under most conditions but could be shortened with early detection (≤ 8 weeks) and high culling capacities (≥ 15% weekly). Under most conditions, the ASFv was eliminated in less than 22 weeks using optimal control radii, although ecological conditions with high rates of wild pig movement required higher culling capacities (≥ 10% weekly) for elimination within 1 year. The results highlight the importance of adjusting response plans based on local ecology and show that wild pig movement is a better predictor of the optimal response area than the number of ASFv cases early in the outbreak trajectory. Our framework provides a tool for determining optimal control plans in different areas, guiding expectations of response impacts, and planning resources needed for rapid elimination

Potential Use for Serosurveillance of Feral Swine to Map Risk for Anthrax Exposure, Texas, USA

Anthrax is a disease of concern in many mammals, including humans. Management primarily consists of prevention through vaccination and tracking clinical-level observations because environmental isolation is laborious and bacterial distribution across large geographic areas diffi cult to confi rm. Feral swine (Sus scrofa) are an invasive species with an extensive range in the southern United States that rarely succumbs to anthrax. We present evidence that feral swine might serve as biosentinels based on comparative seroprevalence in swine from historically defi ned anthrax-endemic and non–anthraxendemic regions of Texas. Overall seropositivity was 43.7% (n = 478), and logistic regression revealed county endemicity status, age-class, sex, latitude, and longitude were informative for predicting antibody status. However, of these covariates, only latitude was statistically signifi cant (β = –0.153, p = 0.047). These results suggests anthrax exposure in swine, when paired with continuous location data, could serve as a proxy for bacterial presence in specifi c areas

Evaluation of the Effect of Hydrated Lime on the Scavenging of Feral Swine (\u3ci\u3eSus Scrofa\u3c/i\u3e) Carcasses and Implications for Managing Carcass-Based Transmission of African Swine Fever Virus

African swine fever (ASF) is a devastating hemorrhagic disease marked by extensive morbidity and mortality in infected swine. The recent global movement of African swine fever virus (ASFV) in domestic and wild swine (Sus scrofa) populations has initiated preparedness and response planning activities within many ASF-free countries. Within the US, feral swine are of utmost concern because they are susceptible to infection, are wide-spread, and are known to interact with domestic swine populations. African swine fever virus is particularly hardy and can remain viable in contaminated carcasses for weeks to months; therefore, carcass-based transmission plays an important role in the epidemiology of ASF. Proper disposal of ASF-infected carcasses has been demonstrated to be paramount to curbing an ASF outbreak in wild boar in Europe; preparedness efforts in the US anticipate carcass management being an essential component of control if an introduction were to occur. Due to environmental conditions, geographic features, or limited personnel, immediately removing every carcass from the landscape may not be viable. Hydrated lime converts to calcium carbonate, forming a sterile crust that may be used to minimize pathogen amplification. Any disturbance by scavenging animals to the sterile crust would nullify the effect of the hydrated lime; therefore, this pilot project aimed to evaluate the behavior of scavenging animals relative to hydrated lime-covered feral swine carcasses on the landscape. At two of the three study sites, hydrated limetreated carcasses were scavenged less frequently compared to the control carcasses. Additionally, the median time to scavenging was 1 d and 6 d for control versus hydrated lime-treated carcasses, respectively. While results of this study are preliminary, hydrated lime may be used to deter carcass disruption via scavenging in the event that the carcass cannot be immediately removed from the landscape

Estimating the economic impact of canine rabies to Viet Nam 2005–2014

The global economic impact of canine rabies has been estimated by several studies. Asia bears a disproportionate burden of this zoonosis due to high levels of human deaths and rates of post-exposure prophylaxis (PEP), but low investment in preventative dog vaccination. The same factors that cause rabies to burden much of Asia are also present in Viet Nam. This study estimated the economic burden of canine rabies in a societal perspective including direct and indirect cost of rabies in dogs, livestock, and humans. Using data collected from personal interviews, published literature, published and supplementary reports, and primary data collection, we estimated the economic impact of canine rabies in Viet Nam over a ten year period (2005–2014). We incorporated the direct and indirect costs for PEP, dog vaccination efforts, livestock losses, and disability adjusted life years (DALYs) into the analysis. General findings from this analysis indicated that over the 10 year study period, the total economic impact of canine rabies was over $719 million USD. The largest portion of impacts (92$1.75 USD. Our results indicate that canine rabies impacts in Viet Nam are consistent with the burden elsewhere reported in Asia, with large expenditures on PEP and very small investments in dog vaccination

Disease Progression and Serological Assay Performance in Heritage Breed Pigs following Brucella suis Experimental Challenge as a Model for Naturally Infected Feral Swine

Invasive feral swine (Sus scrofa) are one of the most important wildlife species for disease surveillance in the United States, serving as a reservoir for various diseases of concern for the health of humans and domestic animals. Brucella suis, the causative agent of swine brucellosis, is one such pathogen carried and transmitted by feral swine. Serology assays are the preferred field diagnostic for B. suis infection, as whole blood can be readily collected and antibodies are highly stable. However, serological assays frequently have lower sensitivity and specificity, and few studies have validated serological assays for B. suis in feral swine. We conducted an experimental infection of Ossabaw Island Hogs (a breed re-domesticated from feral animals) as a disease-free proxy for feral swine to (1) improve understanding of bacterial dissemination and antibody response following B. suis infection and (2) evaluate potential changes in the performance of serological diagnostic assays over the course of infection. Animals were inoculated with B. suis and serially euthanized across a 16-week period, with samples collected at the time of euthanasia. The 8% card agglutination test performed best, whereas the fluorescence polarization assay demonstrated no capacity to differentiate true positive from true negative animals. Froma disease surveillance perspective, using the 8%card agglutination test in parallel with either the buffered acidified plate antigen test or the Brucella abortus/suis complement fixation test provided the best performance with the highest probability of a positive assay result. Application of these combinations of diagnostic assays for B. suis surveillance among feral swine would improve understanding of spillover risks at the national level