FOOT-AND-MOUTH DISEASE VIRUS (FMDV)
LEVELS: Highly unlikely: No controls necessary; Highly unlikely: No evidence of non-foodborne zoonotic transmission; Unlikely to be effective: One or more pathways of farm-to-farm transmission exist that cannot be controlled by on-farm biosecurity; Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s); Substantial: Unsustainable acute or chronic losses related to severe clinical signs in a high prevalence of animals; Prolonged disruption: Measureable negative effect on demand for more than 6 months when disease occurs on one or more farms; Minimal risk: Agent inherently unlikely to develop clinically important resistance to antibacterial or antiviral treatments; Minimal risk: Antibacterial or antiviral treatments rarely occur, or are typically limited to short-course individual animal therapy; No availability: Effective treatments not currently available in the US (or have not been developed); Widely available: Effective commercial vaccines widely available in the US (or held in national response stockpile); Highly likely: Can be eradicated using existing tools and knowledge
OVERVIEW
Foot-and-mouth disease (FMD) is a severe, clinically acute, vesicular disease caused by Foot-and-Mouth Disease Virus (FMDV), an aphthovirus in the family Picornaviridae. FMD affects cloven-hoofed animals including domestic and wild swine as well as ruminants, and is considered the most economically devastating livestock disease worldwide. FMDV has been known in Europe for centuries and was among the first diseases proven to be caused by a filterable agent (1897). Seven serotypes exist (O, A, C, SAT1, SAT2, SAT3, and Asia-1), with no cross-protection between serotypes—infection or vaccination with one serotype does not protect against others. FMDV is endemic in large areas of Africa and Asia, while North America, Australia, New Zealand, and most of Europe are free. The United States has been free since 1929, Canada since 1952, and Mexico since 1954. Clinical disease in pigs is usually severe, characterized by acute fever, vesicles in and around the mouth and on the feet, lameness, and reduced feed intake. Young piglets may die from acute myocarditis ("tiger heart"). Critically for epidemiology, pigs aerosolize approximately 10⁶ TCID50 of virus per day—far more than cattle or sheep—making infected pig operations a major source of airborne spread. Unlike ruminants, pigs do not become persistent carriers of FMDV. Control in free countries relies on early detection, stamping out, and movement restrictions. Multiple effective vaccines exist but require matching to circulating serotypes and strains. The 2001 UK epidemic demonstrated the catastrophic consequences of delayed detection, resulting in the destruction of over 6 million animals and economic losses exceeding £6 billion.
FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No controls necessary
The chapter explicitly states: "FMDV is not zoonotic and therefore not a public health concern." Despite over a century of study and extensive human exposure through farming, veterinary practice, laboratory work, and consumption of products from infected animals, no human infections have been documented. FMDV poses no foodborne risk to consumers of pork or other animal products.
NON-FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No evidence of non-foodborne zoonotic transmission
FMDV does not infect humans through any route. However, the chapter notes that "humans may passively carry the virus in their respiratory tract for a day or more" and that "the role of virus on clothing, boots, etc., is more important in transmission between livestock." Thus, while humans are not susceptible to infection, they serve as mechanical vectors and "the role of people in FMDV transmission is an important consideration in control programs." This mechanical carriage does not constitute zoonotic transmission.
EFFECTIVENESS OF ON-FARM BIOSECURITY IN PREVENTING FARM-TO-FARM TRANSMISSION
Level: Unlikely to be effective: One or more pathways of farm-to-farm transmission exist that cannot be controlled by on-farm biosecurity
FMDV has exceptional capacity to spread despite biosecurity measures due to: (1) Multiple transmission routes: direct contact, contaminated fomites, aerosols, contaminated feed/swill, semen, milk; (2) High viral shedding: pigs aerosolize ~10⁶ TCID50/day, with virus present in all secretions and excretions before clinical signs appear; (3) Environmental stability: virus survives weeks in cool, moist, protein-rich conditions; 2 weeks at 20°C and >6 weeks at 4°C in liquid manure; (4) Long-distance airborne spread: documented transmission from France to Isle of Wight (1981) from infected pig farm; (5) Low infectious dose: cattle can be infected with very small amounts of virus; (6) Wide host range: affects all cloven-hoofed animals, complicating species-specific controls. The virus spreads rapidly within affected holdings and between farms via movement of infected animals (often during the pre-clinical shedding period), contaminated vehicles, personnel, equipment, and feed. Experimental studies confirm that vaccination can reduce but not eliminate transmission. The chapter notes that transmission studies showed "vaccinated pigs became infected and transmitted the virus to other pigs in the same room" when exposed to infected animals, demonstrating that even vaccination cannot fully prevent spread under high-challenge conditions.
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s)
Clinical diagnosis can be challenging because: vesicular lesions are indistinguishable from those caused by SVDV, VSV, SVV, and vesicular exanthema virus; certain FMDV strains may show low virulence for some species; vaccinated animals may show mild or no clinical signs while still transmitting virus; and ruptured vesicles resemble non-specific erosions. However, once FMD is suspected, laboratory confirmation is straightforward with well-established, highly sensitive and specific methods. Real-time RT-PCR is the front-line diagnostic test—rapid, high-throughput, and at least as sensitive as virus isolation. Antigen-capture ELISA can detect and serotype virus from vesicular samples. Virus isolation uses sensitive cell lines (BHK, LFBKαVβ6, IB-RS-2). Serological tests (ELISA, VNT) detect antibodies 3-5 days after clinical signs appear. NSP (non-structural protein) ELISA enables DIVA testing to identify infected animals in vaccinated populations. Pen-side lateral flow devices provide rapid results in field settings. The critical challenge is not laboratory diagnosis but rather the initial recognition that vesicular disease may be present—delayed detection allows extensive spread before control measures begin.
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Substantial: Unsustainable acute or chronic losses related to severe clinical signs in a high prevalence of animals
FMD causes catastrophic losses through multiple mechanisms: (1) Direct mortality: variable depending on strain virulence and animal age; high mortality in young piglets from acute myocarditis; (2) Severe morbidity: affected pigs show high fever (up to 42°C), severe lameness, inability to stand or walk, complete loss of appetite, and dramatic weight loss; (3) Secondary complications: ruptured vesicles predispose to bacterial infections; severe foot lesions may cause claw sloughing ("thimbling"); chronic lameness and wasting in survivors; (4) Control costs: stamping out requires destruction of all susceptible animals on infected and contact premises; the 2001 UK epidemic resulted in destruction of over 6 million animals; (5) Production disruption: movement restrictions prevent normal marketing and animal movements, potentially requiring welfare slaughter of healthy animals that cannot be moved. The severity of clinical disease in pigs exceeds that caused by other vesicular diseases—pigs with FMD become severely debilitated with fever, depression, complete anorexia, and inability to maintain body temperature. Lactating sows develop udder and teat lesions affecting nursing. The economic impact of a single outbreak can reach billions of dollars when direct losses, control costs, and market impacts are combined.
EFFECT ON DOMESTIC OR EXPORT MARKETS
Level: Prolonged disruption: Measureable negative effect on demand for more than 6 months when disease occurs on one or more farms
FMD is the most trade-restrictive animal disease. Detection triggers: immediate WOAH notification; suspension of exports of live animals and animal products to FMD-free countries; establishment of control zones with movement restrictions; potential embargo by all trading partners regardless of geographic distance from affected areas. The 2001 UK epidemic "cost £3.1 billion in losses to agriculture and between £2.7 and £3.2 billion to other industries (such as tourism)." Market recovery requires: completion of stamping out; extensive surveillance to demonstrate freedom; waiting periods (typically 3 months without vaccination, 12 months with vaccination); WOAH recognition of free status; bilateral negotiations with trading partners. Endemic countries face permanent exclusion from premium export markets. Even countries maintaining freedom through vaccination face trade restrictions compared to those free without vaccination. The international recognition system (WOAH disease-free status) creates strong incentives to maintain freedom but also means that any incursion has immediate, severe, and prolonged trade consequences extending far beyond the directly affected region.
PATHOGEN'S ABILITY TO DEVELOP AND SPREAD RESISTANCE
Level: Minimal risk: Agent inherently unlikely to develop clinically important resistance to antibacterial or antiviral treatments
FMDV is a viral pathogen (positive-sense single-stranded RNA virus) that does not carry, acquire, or transmit antimicrobial resistance genes. The virus poses no AMR concerns. However, FMDV shows substantial antigenic diversity: seven serotypes with no cross-protection; multiple strains within each serotype that may reduce vaccine efficacy; and continuous evolution requiring ongoing vaccine strain matching. The O/CATHAY topotype became adapted to infect only pigs (not cattle), demonstrating host-adaptation potential. These represent viral evolution rather than antimicrobial resistance.
AMR DEVELOPMENT DRIVEN BY DISEASE MANAGEMENT
Level: Minimal risk: Antibacterial or antiviral treatments rarely occur, or are typically limited to short-course individual animal therapy
No antiviral treatments exist for FMDV. The primary management approaches are prevention (vaccination in endemic areas) and eradication (stamping out in free areas)—neither involves antimicrobial use. Antimicrobials may be used to treat secondary bacterial infections of ruptured vesicles, but this represents limited, episodic treatment. In stamping-out programs, infected animals are culled rather than treated, eliminating antimicrobial selection pressure. The chapter notes that "antiviral drugs could potentially be used to reduce FMDV replication" but this approach "is likely to be limited since meat will contain drug residues."
AVAILABILITY OF EFFECTIVE TREATMENT OPTIONS
Level: No availability: Effective treatments not currently available in the US (or have not been developed)
No specific antiviral treatments are available for FMDV. Management is entirely preventive (vaccination) or reactive (stamping out). Pigs that survive clear the infection through their own immune response. Supportive care may reduce mortality from secondary complications, but does not address the underlying viral infection. Research on antiviral compounds (e.g., T-1105) has shown some promise experimentally, but "this approach is likely to be limited since meat will contain drug residues and will not be suitable for human consumption." In practice, treatment is not attempted in outbreak situations—infected animals are culled.
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: Widely available: Effective commercial vaccines widely available in the US (or held in national response stockpile)
Multiple highly effective FMDV vaccines are available, developed through decades of research and field use. Modern vaccines are: (1) Inactivated, purified virus produced in cell culture (BHK cells) and adjuvanted; (2) Highly immunogenic when properly matched to circulating strains; (3) Protective within 4-7 days for emergency use, with full protection by 2-3 weeks; (4) Durable for 6-12 months depending on formulation and species. Limitations include: (1) Seven serotypes with no cross-protection—vaccines must include relevant serotypes; (2) Strain variation within serotypes may reduce efficacy against heterologous strains; (3) No sterilizing immunity—vaccines prevent disease and reduce transmission but may not prevent infection; (4) Maternal antibody interference in young pigs (vaccination effective only after 8-12 weeks of age); (5) DIVA challenges—traditional vaccines do not allow easy differentiation of infected from vaccinated animals, though NSP tests provide partial DIVA capability. Emergency vaccination is accepted as a control tool but has trade implications (12-month waiting period for freedom with vaccination vs. 3 months without). The successful eradication of FMD from Western Europe demonstrated that "eradication can be achieved using prophylactic vaccination with good-quality vaccines" when combined with coordinated control efforts.
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Highly likely: Can be eradicated using existing tools and knowledge
The United States successfully eradicated FMDV and has maintained freedom since 1929. Eradication tools are well-established and proven globally: early detection through clinical surveillance and laboratory testing; immediate stamping out of infected and dangerous-contact premises; strict movement restrictions and quarantine; thorough cleaning and disinfection; epidemiological tracing; serological surveillance to demonstrate freedom; and emergency vaccination if needed to slow spread in severe outbreaks. Critical factors for successful eradication include: (1) Early detection—the longer FMDV circulates undetected, the more difficult eradication becomes; (2) Rapid response—"extreme measures are required to eradicate FMDV and, if they are not applied rapidly and effectively, there is a high probability that an outbreak will become an epidemic"; (3) Movement control—experiments confirm that "movement restrictions have more impact than preemptive culling on the success of control"; (4) Feral swine management—preventing establishment of wildlife reservoir is critical (African buffalo maintain SAT serotypes in Africa). Unlike ruminants, pigs do not become persistent FMDV carriers, simplifying eradication from pig populations. If FMDV were reintroduced to the US, eradication would be achievable using established protocols, with success dependent on rapid detection and response before widespread dissemination occurs.