Caliciviruses - VESV
LEVELS: Highly unlikely; Mild; Routine biosecurity keeps it out; Reference or research laboratory required; Minor; Significant disruption; Little; Available, or not needed
| Register id | vesicular_exanthema_of_swine_virus |
| Type | virus |
| Scientific name | Vesicular exanthema of swine virus |
| NCBI taxid | 35612 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Vesicular exanthema of swine is an acute, highly infectious disease causing fever and blisters on the snout, mouth, feet and teats — clinically indistinguishable from foot-and-mouth disease, vesicular stomatitis, swine vesicular disease and Seneca Valley virus infection. It became widespread in the United States during the 1950s, when one serotype spread from California to 41 states, and a vigorous eradication campaign followed; the country was declared free in 1959 and the disease was designated a foreign animal disease. It has not reappeared since. The reason it stays on the register is that the virus never went away, it only left the pigs: the same vesiviruses are widespread in Pacific marine mammals and appear periodically in animals along the western United States, and the original outbreaks are believed to have come from feeding raw fish scraps and untreated garbage. The threat of vesicular disease reappearing in pigs is therefore permanent, and cooking garbage and fish before feeding is the control. There is no treatment and no vaccine — more than forty serotypes are recognised and immunity is serotype- specific, which would probably preclude vaccine development. These viruses are not thought to be of public health significance, though two people have developed blistering lesions after handling infected marine mammals or laboratory virus.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Highly unlikely: Human infection with the agent has never been reported, or has been reported but is not attributed to pig or pork exposure
Basis. ch26 26.2.3, a Public Health section of its own: "These viruses are NOT THOUGHT TO BE OF PUBLIC HEALTH SIGNIFICANCE; however, HUMAN INFECTION BY TWO DIFFERENT MARINE MAMMAL SEROTYPES HAS BEEN REPORTED. SMSV-5 was recovered from vesicular lesions on the palms and soles of A RESEARCHER WORKING WITH THE VIRUS. In a separate incident, an individual who HANDLED DISEASED STELLER SEA LIONS in the Bering Sea developed blistering of the hard palate, upper lip, and facial area. A novel vesivirus (strain McAll) was isolated from throat washings sampled 30 days post onset." 26.2.1: "SMSV isolated from both fish and marine mammals is CAPABLE OF PRODUCING VESICULAR EXANTHEMA IN PIGS AND HUMANS." 26.2.4 lists the natural host range: "pigs, pinnipeds, cetaceans, cattle, horses, skunk, PRIMATES (INCLUDING HUMANS), reptiles, and fish." shic_vesv: "VESV has occasionally been isolated from humans with blisters; however, the virus is not considered to be a serious public health threat."
How this level was decided
MOVED L2 -> L1, re-read 2026-09-04 AGAINST THE REWORDED LABELS. ch26 26.2.3: two people have been infected and NEITHER CASE CAME FROM A PIG -- one a laboratory worker handling the virus, the other a handler of diseased Steller sea lions, both marine mammal serotypes.
PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: Level 2. Human infection with this group of viruses is not speculative -- two people have been infected and both developed the same vesicular lesions the pigs get -- but NEITHER CASE CAME FROM A PIG. One was a laboratory worker handling the virus, the other handled diseased sea lions, and both involved marine mammal serotypes. Under C1 as rescoped to transmission FROM PIGS, that is the level 2 label exactly: plausible, since the virus plainly infects people on contact with infected animals and pigs develop the same lesions that transmitted it, but never reported from a pig. It is not level 3, because no foodborne or occupational route from pigs has been described and no control point exists to fail -- helped by the fact that VES has not been in a US pig since 1959. Level 1 held. Isolation from human blisters is a real finding, but it is not attributed to pig exposure -- the marine vesiviruses circulate in pinnipeds along the Pacific coast, and VESV has not existed in swine anywhere since eradication.
C2 Zoonotic impact
Severity of human illness caused by the agent
Mild: Human illness is usually mild and self-limiting, and serious disease occurs only rarely
Basis. ch26 26.2.3: the two reported human infections produced "vesicular lesions on the palms and soles" in one case and "blistering of the hard palate, upper lip, and facial area" in the other. No systemic illness, hospitalisation, sequela or death is described, and the section opens by saying these viruses are not thought to be of public health significance. shic_vesv: "the virus is not considered to be a serious public health threat."
How this level was decided
Level 2. The two human cases on record are self-limiting blistering of skin and oral mucosa, which is the level 2 label -- usually mild and self-limiting, with serious disease only rare. It is not level 1, because level 1 says pigs are not a source of human illness at all and the virus demonstrably does infect people; the C1 cell carries the reason no case has come from a pig. Level 2 confirmed -- blisters, not serious.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Routine biosecurity keeps it out: Quarantine of incoming stock, transport and fomite control, cleaning and disinfection, and the usual monitoring reliably exclude it
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c3l3, this seems to have been a unique historic case and seems like most regulatory officials would just like to ignore it. Seems very likely that routine biosecurity will keep it out of herds"
Basis. ch26 26.2.8: "Garbage and fish should be COOKED before being fed to pigs. Although VES has not reappeared since its eradication in the 1950s, VES-LIKE VIRUSES ARE WIDESPREAD IN THE PACIFIC OCEAN and periodically appear in domesticated and captive wildlife along the western United States. THE POTENTIAL FOR VESICULAR DISEASE TO APPEAR IN PIGS REMAINS AN EVER-PRESENT THREAT." 26.2.4: "The principal form of transmission during outbreaks of vesicular exanthema in the United States was thought to be BY FEEDING UNTREATED CONTAMINATED GARBAGE. However, spread by direct contact of infected animals occurs readily." The reservoir is marine: VESV/SMSV and related viruses "have been found along the Pacific Coast of North America as far north as the Bering Sea", isolated from sea lions, fur seals, elephant seals, a sea lion liver fluke, a mussel, and perch-like fish in tidal pools off southern California. 26.2.1: the United States was declared free of VES in 1959 and it "has never been reported as a natural infection of pigs in any other parts of the world". shic_vesv: "The 1932 outbreak was linked to feeding of uncooked garbage and fish scraps to pigs." "To prevent infection with VESV, all garbage and fish fed to swine must be cooked to 100C for 30 minutes." "Other marine vesiviruses remain prevalent along the Pacific coast of the United States." "Caliciviruses are stable in the environment and resistant to heat."
How this level was decided
Level 3, and FLAGGED AS A LEVEL 3 OR LEVEL 5 JUDGMENT, because this entry has the clearest permanent non-pig reservoir in the batch and the narrowest route out of it. LEVEL 3 IS SCORED because the route into a herd is a feed practice and nothing else: raw garbage or uncooked marine product. Cooking it is routine, it is already required by law for US swine feeding, and closing that route has kept the disease out of US pigs for 66 years -- which is what "routine biosecurity keeps it out" means. THE LEVEL 5 ARGUMENT is that the L5 label asks for a permanent US reservoir outside the farm and the industry that no farm or industry action removes, and marine caliciviruses along the Pacific coast are exactly that: they are in sea lions, seals, fish and shellfish, they periodically appear in coastal wildlife, and the chapter calls the threat ever-present in its own words. NOTE HOW THIS DIFFERS FROM THE ASF CASE Eric ruled on. There the reservoir would establish IN pigs -- feral swine -- and no action removes it once there. Here the reservoir cannot establish in pigs at all: the virus was eradicated from US swine in 1959 and has not returned in 66 years, because the only bridge is one that producers control. The comparable entry already scored is swine_vesicular_disease_virus at level 3. Level 3 held, and the boundary is worth stating because thermally treated feed appears on the level 4 list. Cooking garbage and fish scraps before feeding is not that: it is a long-standing legal requirement and ordinary practice, not an extraordinary measure adopted against this agent. The reservoir is marine mammals rather than pigs, and it reaches pigs only through uncooked waste.
C4 Detection difficulty
Difficulty of recognizing and confirming infection
Reference or research laboratory required: A validated assay exists, but only at a national reference or research laboratory rather than at local or regional level
Basis. ch26 26.2.1: "In pigs, the clinical disease is INDISTINGUISHABLE FROM foot-and-mouth disease, vesicular stomatitis, swine vesicular disease, and vesicular disease caused by Seneca Valley virus." 26.2.6: "Laboratory differentiation of VESV from other vesicular disease-causing viruses... IS ESSENTIAL. Virus may be detected by a variety of antibody tests, including complement fixation, virus neutralization, and ELISA. HOWEVER, THE ANTIBODY TESTS RELY ON SPECIFIC ANTISERA FOR EACH SEROTYPE." 26.2.2 records how many that is: more than 40 serotypes in the species, of which 13 are VESV and 17 SMSV, and "seven VESV serotypes isolated during the 1930s and 1940s have since been LOST OR DESTROYED and have not been compared with later serotypes". "Various reverse transcription-polymerase chain reaction (RT-PCR) assays HAVE BEEN DEVELOPED for the identification of vesiviruses." shic_vesv: "VESV can be grown in cell culture. Electron microscopy, reverse transcriptase polymerase chain reaction (RT-PCR), and real-time RT-PCR can be used." "VESV-induced vesicular disease is clinically indistinguishable from vesicular disease caused by foot-and-mouth disease virus, vesicular stomatitis virus, swine vesicular disease virus, or Seneca Valley virus."
How this level was decided
Level 3, matching foot-and-mouth disease, classical swine fever and African swine fever, which are the worked examples at that level. A validated assay exists -- RT-PCR for vesiviruses, virus isolation in pig or monkey kidney cells, and serotype-specific serology -- but this is a foreign animal disease whose whole diagnostic purpose is to be told apart from FMD, and that differentiation is national reference laboratory work rather than something a regional laboratory does. It is not level 4: assays of known reliability exist. NOTE THE SEROTYPE PROBLEM, which is a real limit on the serological route rather than on the level: antibody tests need specific antisera for each of more than forty serotypes, and seven of the historical ones no longer exist to be compared against. Level 3 confirmed.
C5 Production cost
Financial impact on the infected farm's cost of production
Minor: Small and generally short-lived losses with little effect on overall cost of production
Basis. ch26 26.2.1: "Vesicular exanthema of swine (VES) is an acute, highly infectious disease characterized by fever and formation of blisters on the snout, oral mucosa, soles of the feet, the coronary band, and between the toes." 26.2.5: vesicles appear at the snout, lips, tongue, oral mucosa, sole, interdigital space and coronary band, and "lesions may also appear on the teats, particularly in nursing sows". 26.2.7: recovered animals "develop a strong immune response and are protected against the same serotype for at least 6 months". No mortality figure, no morbidity figure and no cost figure appears anywhere in section 26.2, and no death is described. shic_vesv: "VESV is highly infectious in swine and can cause morbidity of up to 90%." "VESV has also been associated with reproductive failure in swine and mild encephalitis."
How this level was decided
Level 2, and set deliberately level with swine_vesicular_disease_virus, which is the same shape of disease and is already scored there. What the chapter describes is fever and vesicles that rupture within 24 to 48 hours, lameness from foot lesions, and recovery with solid serotype-specific immunity -- painful, and costly through lost intake and lameness and mastitis where the teats are involved, but short-lived and not fatal. Small and generally short-lived losses. IT IS NOT SCORED ON THE REGULATORY CONSEQUENCE, which would be far larger: a vesicular lesion in a US pig triggers a foreign animal disease investigation and a movement standstill. That consequence is what C6 measures, and counting it here as well would count it twice, which PAPRIKA cannot see because it adds the criteria. Level 2 held, with the pull upward recorded: 90% morbidity is a large number. Held because the disease is vesicular and self-limiting rather than fatal, the losses are production interruption rather than death, and the agent does not currently exist in swine anywhere in the world.
C6 Market impact
Duration of material disruption to pork and pig markets
Significant disruption: Material negative effect on supply or demand lasting 1 to 6 months when disease occurs on one or more farms
Basis. ch26 26.2.1: VES "became widespread in the United States during the 1950s, but a vigorous campaign to eradicate the disease was successful. In 1959, the United States was declared free of VES, AND THE DISEASE WAS DESIGNATED A FOREIGN ANIMAL DISEASE." 26.2.4 gives the precedent: outbreaks between 1932 and 1951 were confined to California, but "in 1951, ONE SEROTYPE (B51) SPREAD TO 41 STATES AND THE DISTRICT OF COLUMBIA. Two further serotypes appeared in New Jersey in 1954 and 1956." 26.2.8: "Suspected cases of vesicular exanthema should be REPORTED IMMEDIATELY TO THE PROPER AUTHORITIES." 26.2.1: the clinical disease is indistinguishable from foot-and-mouth disease. shic_vesv: "The virus was eradicated and is now considered a foreign animal disease." "VESV-induced vesicular disease is clinically indistinguishable from... foot-and-mouth disease virus."
How this level was decided
Level 3, and level with swine_vesicular_disease_virus for the same reason. There is a real US precedent to reason from rather than a hypothetical, which is what the standing note on market_impact asks for: a serotype reached 41 states in 1951 and it took a federal eradication campaign running to 1959 to clear it. A vesicular lesion in a US pig today is a reportable foreign animal disease event that cannot be distinguished from FMD at the pen side, so it stops movement and export while the laboratory differentiates -- a material disruption lasting one to six months. It is not level 4, because the disease itself is mild and the confusion resolves once the laboratory reports; FMD sits at level 4 and this should not. Level 3 confirmed. A foreign animal disease presenting as an FMD-lookalike triggers the full investigation and the movement controls that go with it.
C7 Treatment potential
Potential for treatment to improve outcomes
Little: Effective pathogen-directed treatment is available and works, or animals recover acceptably without it
Basis. ch26 26.2.8: "NO SPECIFIC TREATMENT IS AVAILABLE for VESV infection." 26.2.6: vesicles "normally rupture within 24-48 hours to form erosions". 26.2.7: "Animals that have recovered from VESV develop a strong immune response and are protected against the same serotype for at least 6 months."
How this level was decided
Level 1 on the second clause of the label -- animals recover acceptably without treatment. C7 asks whether a treatment that does not exist would be worth having, and here it would not: the lesions rupture within two days, the animals recover, and immunity follows. Nothing about the outcome would meaningfully improve with an antiviral. This matches foot-and-mouth disease, swine vesicular disease and Seneca Valley virus, all three of which are scored at level 1 for the same reason -- the problem these viruses present is regulatory, not clinical, and C7 does not measure that. Unchanged.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Available, or not needed: Effective vaccines are widely available in the US or secured for national outbreak response, or the disease does not clinically or economically justify vaccinating
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED AT LEVEL 1, AND HE WROTE NO LEVEL AGAINST THIS CELL. His whole answer was "No market imperative to develop a vaccine", which harvest_markup.py correctly refused to apply because prose without a level comes back to him rather than being guessed at. It is read as c8l1 for two reasons: the phrase is the C8 level 1 "not needed" clause in its own terms, and he used the same words WITH the level on the neighbouring cell in the same sheet -- "c8l1, no clinical or market imperative to develop a vaccine" on saint_valerien_like_virus. A dropped prefix rather than an ambiguity. THE CELL WAS ALREADY AT LEVEL 1 and the pass had flagged it as a level 1 or 3 question, because the chapter says the forty-plus serotypes "would probably preclude" a vaccine -- a technical impossibility rather than an absence of need. His answer settles it on need: there is no imperative, so level 1 stands.
Basis. ch26 26.2.8: "VACCINES ARE NOT AVAILABLE, AND THE NUMBER OF SEROTYPES WOULD PROBABLY PRECLUDE THEIR DEVELOPMENT." 26.2.2: more than 40 serotypes are recognised in the species, "although not all have been serologically compared". 26.2.7: recovery protects against THE SAME SEROTYPE for at least 6 months. 26.2.1: the disease was eradicated from the United States by 1959 by a campaign, not by vaccination. shic_vesv: "There are currently no available vaccines for VESV." "Development of a vaccine for VESV is complicated by the presence of multiple serotypes." "VESV does not currently exist in swine anywhere in the world."
How this level was decided
Level 1 on the "not needed" clause, and level with swine vesicular disease and foot-and-mouth disease, both scored there. There is certainly no vaccine, so the whole question is whether the disease would justify one, and it would not: the disease was eliminated from the United States by movement control and slaughter and has stayed out for 66 years, the clinical disease is mild and self-limiting, and immunity is serotype-specific across more than forty serotypes so a vaccine could not protect broadly even if built. FLAGGED AS A LEVEL 1 OR 3 JUDGMENT for one reason only: the chapter says the serotype count would PRECLUDE development, which is a technical impossibility rather than an absence of need, and if the view is that a vaccine would be wanted for outbreak response the way the FMD bank is, this is level 3. Level 1 confirmed. No clinical or market imperative for a vaccine against an agent that exists in no pig anywhere -- and forty serotypes would make one impractical. This is the affirmatively supported use of level 1, not an inference from silence.
Levels and evidence are generated from data/assignments/vesicular_exanthema_of_swine_virus.yml; the overview is authored in data/overviews/vesicular_exanthema_of_swine_virus.md. Do not hand-edit this page — corrections go in data/assignments/CORRECTIONS.yml.
Quoted material marked Basis is from Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW, Zhang J, eds. Diseases of Swine, 12th edition. Hoboken: Wiley Blackwell, 2025 — except where another source is named in the quotation itself.