Vesicular Stomatitis Virus
LEVELS: Sometimes occurs; Mild; Extraordinary biosecurity required; Reference or research laboratory required; Minor; Significant disruption; Little; Available but inconsistent
| Register id | vesicular_stomatitis_virus |
| Type | virus |
| Scientific name | Vesicular stomatitis virus |
| NCBI taxid | 11276 |
| Evidence | 3 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Vesicular stomatitis is another of the vesicular diseases whose lesions in pigs cannot be distinguished from those of foot-and-mouth disease, and it is the only one of them that occurs naturally in the United States, in periodic epidemics across the southwestern states. In pigs it causes blisters in the mouth and on the feet with excessive salivation, lameness, pain, loss of appetite and weight; in severe cases the claw separates. Morbidity in an outbreak can reach 90% among animals in direct contact, mortality is low, and pigs usually recover in two to three weeks. Unusually among these agents it is spread by insects — black flies and biting midges are accepted as important vectors during epidemics, which fits the way outbreaks move across the landscape — as well as by direct contact and contaminated buckets and equipment, including from pigs showing no signs. The economic loss is as much regulatory as clinical: affected premises are quarantined and movement stops until the laboratory has excluded foot-and-mouth disease. Treatment is palliative — soft feed, padding, antiseptics and antibiotics for secondary infection. No vaccine is available in North America, though inactivated vaccines are used in endemic South American countries. It is a genuine zoonosis, causing an influenza-like illness with fever and occasionally blisters in people who handle affected animals or work with the virus, but no severe human disease is described.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Sometimes occurs: Known risk of transmission to humans (foodborne or occupational), but requires failure of one or more control points for transmission to humans
Basis. ch39 39.2.3, a Public Health section of its own: "VSV IS A ZOONOTIC AGENT AND HUMANS CAN BECOME INFECTED BY DIRECT CONTACT WITH LESIONED ANIMALS or in laboratory settings by aerosolization of virus... In addition, PEOPLE LIVING IN ENDEMIC AREAS PRESENT SEROLOGICAL EVIDENCE OF INFECTION but do not report severe symptoms of disease, suggesting they likely had NATURAL EXPOSURE TO LOWER DOSES OF VIRUS (E.G. BY INSECT BITE)." 39.2.4 on what a lesioned pig is shedding: "virus can be isolated in HIGH CONCENTRATIONS from vesicular fluid, throat swabs, tonsils, oral fluid, and epithelium of clinically affected animals for up to 10 days post infection", and ruptured vesicles release "straw-colored, VIRUS-RICH EXUDATES". cfsph_2016 is in the folder as the second source. shic_vsv: "Humans in direct contact with infected animals or tissues can be infected with VSV; however, disease is mild and self-limiting."
How this level was decided
Level 3. The chapter says outright that people are infected by direct contact with lesioned animals, which is a known occupational risk, and the control point that has to fail is obvious and ordinary: handling an animal with ruptured vesicles releasing virus-rich fluid, without gloves. That is the level 3 label. IT IS NOT LEVEL 4, and the distinction is worth stating because this is a vector-borne virus: the insect route delivers VSV to people directly from the fly, not from the pig, and C1 as rescoped scores only transmission FROM PIGS. A person bitten by an infected black fly did not catch it from a pig. NOTE ALSO that the seropositive residents of endemic areas are evidence the virus reaches people readily, but not evidence about which route brought it. Level 3 confirmed -- direct contact with infected animals transmits to people.
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. ch39 39.2.3: "CLINICAL SIGNS IN PEOPLE INCLUDE FLU-LIKE SYMPTOMS, FEVER, PHOTOPHOBIA, AND IN RARE CASES, BLISTER-LIKE LESIONS appearing 1-2 days after exposure." "People living in endemic areas present serological evidence of infection BUT DO NOT REPORT SEVERE SYMPTOMS OF DISEASE." No hospitalisation, sequela or death from vesicular stomatitis in a person is described anywhere in the chapter or in cfsph_2016. shic_vsv: "disease is mild and self-limiting."
How this level was decided
Level 2. The label asks for illness that is usually mild and self-limiting with serious disease only rare, and that is the whole clinical description on record: a few days of influenza-like illness, sometimes with photophobia, occasionally with blisters. The serological evidence from endemic areas points the same way -- people who have plainly met the virus report nothing worth reporting. It is not level 3, because nothing here commonly requires medical treatment, and not level 1, because the virus demonstrably does infect and sicken people. Level 2 confirmed by direct statement.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Extraordinary biosecurity required: Exclusion needs measures beyond the routine, such as air filtration, thermally treated feed and bedding, or repeated costly testing to find carriers, and may still fail
Basis. ch39 39.2.4: "TRANSMISSION BY ARTHROPOD VECTORS IS WIDELY ACCEPTED AS AN IMPORTANT MEAN of virus transmission during epidemics and is consistent with disease distribution patterns. TWO MAIN GROUPS OF BIOLOGICAL VECTORS, BLACK FLIES (SIMULIUM SPP.) AND BITING MIDGES (CULICOIDES SPP.), seem to play pivotal roles during VS epidemics in the United States." The virus is also spread by direct contact and fomites: "VSNJV can remain viable in contaminated saliva on pails or food buckets for 3-4 days", and transmission by contact occurs "from both clinically and SUBCLINICALLY INFECTED PIGS". 39.2.9 lists the control measures: "insect control, HOUSING ANIMALS INDOORS DURING PEAK INSECT FEEDING TIMES, and implementation of biosecurity procedures designed to avoid the introduction of VSV from affected premises via equipment, personnel, or animals. INSECT REPELLANTS, such as permethrin or other repellants approved for use in swine, should also be considered. Additional measures... include INSECT VECTOR ABATEMENT MEASURES." 39.2.4: in the western United States "epidemics of VSNJV and, to a lesser extent VSIV, generally occur in horses and cattle at 5- to 10-year intervals", and there is "extensive serological documentation of infection in DEER AND FERAL SWINE in the southeastern United States". shic_vsv: "VSV is transmitted through direct contact and by insect vectors. Sand flies (Phlebotomus and Lutzomyia species), black flies (Simuliidae family), and mosquitoes (Aedes species) are confirmed carriers of some strains of VSV." "In endemic areas, outbreaks of VSV occur in warmer months and along waterways. VSV is also capable of overwintering in countries such as the United States."
How this level was decided
Level 4, and it sits with the mosquito-borne arboviruses for the same reason. Under C3 as settled on 2026-09-03 the question is what a US herd must do to keep the agent out, and here the answer is vector abatement, repellents and timing the animals indoors around fly activity -- measures beyond the routine, which is the level 4 label, and which may still fail because black flies and midges are not excluded by a building the way a feral pig is. IT IS NOT LEVEL 2, even though housing helps: housing is offered as one measure among several rather than as the answer, and the contact and fomite routes survive it. NOTE THE SUBCLINICAL CARRIER, which is why a quarantine-only programme would not do it either: pigs infected by insect bite at a non-lesion site develop antibody with no lesions and can still transmit by contact. Level 4 confirmed. Three confirmed insect vector families, which under the standing rule housing does nothing about, plus demonstrated overwintering in the US.
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. ch39 39.2.7: "In swine, VSV infection is CLINICALLY INDISTINGUISHABLE FROM FMDV, SVDV, VESV, OR SVV, but a complete list of rule-outs for causes of vesicular disease in swine also includes porcine parvovirus, enterovirus infection, and swinepox virus. Noninfectious causes include trauma... THEREFORE, IT IS IMPERATIVE TO COLLECT AND SUBMIT DIAGNOSTIC SAMPLES FOR LABORATORY TESTING." On the assays: "REAL-TIME PCR PANELS ARE HIGHLY SENSITIVE AND RAPID TESTS THAT CAN IDENTIFY VSV SEROTYPE AND RULE OUT OTHER VESICULAR AGENTS", with virus isolation in Vero or BHK-21, antigen-capture ELISA, and serology by virus neutralisation, complement fixation and ELISA. The sampling is exacting: vesicular fluid preferred, transport in Tris-buffered tryptose broth chilled to 4 degrees, and "FREEZING SHOULD BE AVOIDED as this can adversely affect virus detection". 39.2.9: "When vesicular disease is observed in swine, steps should be taken to STOP THE MOVEMENT OF ANIMALS onto or off the premises until a diagnosis is made. THE APPROPRIATE ANIMAL HEALTH AUTHORITIES SHOULD BE NOTIFIED IMMEDIATELY." shic_vsv: "National reference laboratories often identify VSV by complement fixation (CF) assays, electron microscopy, and virus isolation, as VSV is easily propagated in cell culture." "Clinical signs caused by VSV cannot be distinguished from other vesicular diseases of swine."
How this level was decided
Level 3, level with foot-and-mouth disease, classical swine fever, African swine fever, swine vesicular disease and vesicular exanthema -- every vesicular agent in the register sits here and that consistency is the point. A validated assay plainly exists: the real-time PCR panel is designed to serotype VSV and exclude the other vesicular viruses in one run. What puts it at level 3 rather than level 2 is that a vesicular lesion in a pig is a notifiable event whose whole diagnostic purpose is to be told apart from foot-and-mouth disease, and that differentiation is national reference laboratory work, not something a regional laboratory attempts. Level 3 confirmed in the factsheet's own words -- national reference laboratories do the identification.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c5l2, agent can cause clinical disease but this is of minor significance"
Basis. ch39 39.2.6: "MORTALITY DUE TO VSV INFECTION IS LOW, BUT MORBIDITY RATES DURING AN OUTBREAK CAN BE AS HIGH AS 90%, especially among animals in direct contact. VESICULAR STOMATITIS IS USUALLY A SELF-LIMITING DISEASE IN PIGS AND ANIMALS TYPICALLY RECOVER IN 2-3 WEEKS, if there are no complications from secondary bacterial infections." The cost while it lasts: "excessive salivation due to lesions in the mouth and LAMENESS due to foot lesions may be observed. PAIN ASSOCIATED WITH ORAL LESIONS CAN LEAD TO ANOREXIA AND WEIGHT LOSS", and in severe cases "the claw may separate". 39.2.4: "outbreaks in free-range and small-scale open pig farms can be SEVERE", and 39.2.1 records that naturally occurring VSNJV in US domestic swine has not been reported since 1968. shic_vsv: "Morbidity rates vary widely, but can be high (up to 90%) in some herds. Adult animals are most affected. Death due to VSV is uncommon." "Reluctance to eat and weight loss can occur due to vesicle-related discomfort."
How this level was decided
Level 2, and set level with swine vesicular disease and vesicular exanthema, which are the same shape of disease and are already scored there. What the chapter describes is a fortnight of painful mouths and feet in up to 90% of the group, with anorexia and weight loss while it lasts and near-complete recovery after it -- small and generally short-lived losses. FLAGGED LIGHTLY AS A LEVEL 2 OR 3 JUDGMENT, because 90% morbidity with claw separation in the severe cases is at the top of what level 2 will carry, and the chapter says outbreaks in open pig farms can be severe. IT IS NOT SCORED ON THE MOVEMENT RESTRICTION, which the chapter names as the other half of the economic loss: that is what C6 measures, and counting it here as well would count it twice. Level 2 confirmed -- high morbidity but death uncommon, so the loss is weight and interruption rather than mortality.
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. ch39 39.2.1, stating both halves of the loss: "During VS outbreaks, AFFECTED PREMISES ARE QUARANTINED and diagnostic samples submitted to rule out these diseases. Thus, THE ECONOMIC LOSSES ASSOCIATED WITH VS INCLUDE BOTH THE DIRECT IMPACT OF CLINICAL DISEASE ON PRODUCTION AND THE INDIRECT EFFECT OF MOVEMENT RESTRICTIONS PLACED ON AFFECTED PREMISES." 39.2.9: "When vesicular disease is observed in swine, steps should be taken to STOP THE MOVEMENT OF ANIMALS onto or off the premises until a diagnosis is made. The appropriate animal health authorities should be notified immediately." cfsph_2016 records the international dimension: control matters "in preventing vesicular stomatitis outbreaks, WHICH CAN RESTRICT INTERNATIONAL TRADE". The US precedent is recurring rather than hypothetical: western US epidemics at 5- to 10-year intervals, most recently the 2023 California outbreak. shic_vsv: "VSV is the most common vesicular disease of livestock in the Americas." "The last reported incidence of VSV-NJ infection in domestic swine in the United States was in 1968. Naturally occurring VSV-IND infection in swine has never been reported in the United States."
How this level was decided
Level 3, level with swine vesicular disease and vesicular exanthema of swine virus. This is the scoreable case the standing note SCORING/market_impact asks for -- something has actually happened, repeatedly, in the United States. A vesicular lesion in a pig cannot be told from foot-and-mouth disease at the pen side, so it stops movement onto and off the premises and is reported to authorities the same day, and the chapter names movement restriction as a named component of the economic loss rather than a hypothetical. Material disruption lasting one to six months. It is not level 4: the confusion resolves once the laboratory reports, which is what separates every vesicular look-alike from foot-and-mouth disease itself. Level 3 held. A vesicular disease in a pig triggers a foreign animal disease investigation and movement controls regardless of which virus it turns out to be. Worth noting the factsheet's detail that no US pig has had VSV-NJ since 1968, so the swine precedent is old -- but VSV outbreaks in US cattle and horses are recent and regular, and their handling is the precedent to reason from.
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. ch39 39.2.9: "As with most viral infections, TREATMENT OF VSV-INFECTED ANIMALS IS FOCUSED ON ALLEVIATING PAIN, FEVER, AND DISTRESS. PALLIATIVE CARE INCLUDES FEEDING SOFT FEED AND PROVIDING PADDING FOR HARD SURFACES. Antibiotics may be useful to prevent or treat secondary bacterial infections. Treatment of vesicular lesions with topical antiseptics may promote faster healing and reduce the risk of secondary infections." 39.2.6: "vesicular stomatitis is usually a SELF-LIMITING disease in pigs and animals typically RECOVER IN 2-3 WEEKS", with lesions re-epithelialising 5-10 days after eruption.
How this level was decided
Level 1 on the second clause -- animals recover acceptably without pathogen-directed treatment -- and the chapter supports it directly: the disease is self-limiting, the lesions heal in a fortnight, and what the veterinarian does is soft feed, padding and pain relief. That supportive care is not a pathogen-directed treatment, so it does not carry level 1 by itself; the recovery does. This matches foot-and-mouth disease, swine vesicular disease, vesicular exanthema and Seneca Valley virus, all scored level 1 on the same structure -- the problem a vesicular virus presents is regulatory, not clinical, and C7 does not measure that. Unchanged.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Available but inconsistent: Commercial or autogenous vaccines exist in the US but protection may be inconsistent
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c8l2, there are options for vaccination of pigs but these are unproven" THIS CONFIRMS THE BLUE EYE READING RATHER THAN THE EDEMA DISEASE ONE, and the pass had flagged exactly that choice. Both entries present the same facts -- a commercial vaccine that exists abroad and not in the US, for a disease the US does not have -- and he has now used the same answer twice: level 2, because a product exists and its protection is unproven. "There are options for vaccination of pigs but these are unproven." The E. coli edema disease reading, where he took level 1 on the ground that it is not needed anyway, is the exception rather than the pattern.
Basis. ch39 39.2.9, the last two sentences of the chapter section: "THERE ARE NO COMMERCIALLY AVAILABLE VACCINES IN NORTH AMERICA to prevent VS. HOWEVER, INACTIVATED VACCINES ARE COMMERCIALLY AVAILABLE AND ARE USED TO PROTECT PIGS AGAINST CLINICAL VS IN SOUTH AMERICAN COUNTRIES WHERE VSV IS ENDEMIC." 39.2.4: naturally occurring VSNJV in US domestic swine has not been reported since 1968, and VSIV has never been reported in US swine.
How this level was decided
Level 2, on the reading Eric applied to blue eye disease on 2026-09-03 rather than the one he applied to E. coli edema disease. The two cases look identical on the page -- a commercial vaccine that exists abroad and not in the US, for a disease the US does not have -- and he moved blue eye UP from level 1 to level 2 because products exist and are used and nobody knows how well they work. The same is true here, and more strongly: these are commercial inactivated vaccines given routinely to pigs in endemic South American countries, not autogenous products. Level 2 records that a vaccine exists whose protection is unproven from a US standpoint. FLAGGED AS A LEVEL 1 OR 2 JUDGMENT, because the edema disease reading is also available -- no US case since 1968 means no US herd needs one, which is the "not needed" clause. Unchanged.
Levels and evidence are generated from data/assignments/vesicular_stomatitis_virus.yml; the overview is authored in data/overviews/vesicular_stomatitis_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.