Seneca Valley Virus
LEVELS: Highly unlikely; No human illness; Routine biosecurity keeps it out; Laboratory-dependent; Moderate; Temporary disruption; Little; Needed but not available
| Register id | seneca_valley_virus |
| Type | virus |
| Scientific name | Senecavirus A |
| NCBI taxid | 390157 |
| Evidence | 3 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Senecavirus A, better known as Seneca Valley virus, causes a vesicular disease of pigs: blisters and erosions on the snout and around the top of the hoof, with lameness affecting up to 80-90% of pigs in an outbreak. Adults rarely die and lesions heal in about two weeks, but in Brazil 20-30% mortality was recorded in newborn piglets on farms where sows had developed lesions the week before, with some reports as high as 70% in piglets four days old or younger. The reason this virus matters far more than that description suggests is diagnostic: its lesions are indistinguishable from those of foot-and-mouth disease, swine vesicular disease, vesicular stomatitis and vesicular exanthema, so every case triggers a foreign animal disease investigation until the laboratory rules those out. It has been isolated from pigs in at least ten US states, and cases have risen alongside the rise in vesicular disease reports. Mice and house flies on affected farms carried genetically identical virus, and viable virus has been recovered from spiked feed 37 days later, so feed and vermin are plausible routes. No commercial vaccine is available, though experimental inactivated and live-attenuated candidates have protected pigs. It has no known public health significance — one isolate is being developed as a cancer therapy because it kills cancerous but not normal human cells.
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. ch36 36.6.3: "SVV has no known public health significance. In fact, one isolate, SVV-001, has been developed as a cancer therapy due to its ability to kill cancerous, but not normal, human cells." shic_sva: "Neutralizing antibodies to SVA have been detected in small populations of swine, cattle, and wild mice in the United States. SVA nucleic acids have been detected in mice and houseflies in addition to pigs."
How this level was decided
Level 1, and the second sentence is unusually strong evidence for a negative. SVV has been deliberately administered to human cancer patients as an oncolytic therapy on the basis that it does not harm normal human cells. An agent given to people on purpose without causing disease is not a zoonotic risk from pigs. Level 1 confirmed. The host range that has been looked at is animal; no human involvement is reported.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. ch36 36.6.3: "SVV has no known public health significance", and SVV-001 kills "cancerous, but not normal, human cells".
How this level was decided
C2 scores level 1 whenever the agent does not cause disease in people. Its selective sparing of normal human cells is the basis of its therapeutic use. Unchanged.
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
Basis. ch36 36.6.4: "Detection of infectious SVV in mice in the natural environment and susceptibility of mice to SVV inoculation under experimental conditions suggest that mice may act as a secondary host for the virus." "SVV has been isolated from mice and house flies on a farm where SVV vesicular disease was diagnosed. Nucleotide sequence studies showed that the viruses present in pigs, mice, and flies were essentially identical." "An investigation of SVV in Brazil showed that SVV RNA was present in feed and/or ingredients... infectious SVV could be recovered even 37 days post spiking." shic_sva: "a retrospective serosurvey showed that the virus had been circulating silently in U.S. pigs since at least 1988." "SVA was identified in a single U.S. pig with vesicular lesions in 2010. Since July 2015, the virus has increasingly been identified in clinically affected pigs in the United States." "SVA nucleic acids have been detected in mice and houseflies in addition to pigs."
How this level was decided
MOVED L5 -> L3 on 2026-09-03, when C3 was reduced to four levels and the whole level 5 block was re-read against the exclusion test rather than the reservoir test. Eric: "C3 is about exclusion, not reservoirs per se, though the two are related", and "who cares about reservoirs? Reservoirs really don't matter as long as you keep domestic pigs from becoming infected through biosecurity implementation." THE PREVIOUS LEVEL WAS NEVER JUDGED: this entry carried a RENUMBERED L4 -> L5 stamp from 2026-09-01, meaning it was moved past the newly created housing level rather than assessed against it. mice and house flies were isolated on a farm with SVV vesicular disease. Rodent and fly control is a routine programme. NOTE that level 1 is arguable on different grounds -- SVV is endemic in US pigs -- and that question is left open rather than settled here.
EARLIER REASONING, kept because it is the evidence read: RENUMBERED L4 -> L5 on 2026-09-01, when C3 went from four levels to five. The argument below is unchanged and so is the judgment. What changed is the scale it sits on. C3 now runs on the EFFORT REQUIRED TO EXCLUDE: L1 already in the herd, L2 housing alone keeps it out, L3 routine biosecurity keeps it out, L4 extraordinary biosecurity required, L5 exclusion may not be achievable. Mice and house flies on affected farms carrying sequence-identical virus is a reservoir outside the pig industry, and feed is a route C3 names specifically -- infectious virus survived 37 days in spiked feed ingredients. Neither is closed by farm-gate biosecurity. Level 4. *** LEVEL 3 HELD BUT FLAGGED, and this is the second-strongest flag of the round after porcine_reoviruses C4. *** The factsheet states that SVA has been circulating in US pigs since at least 1988 and has been increasingly identified in clinically affected US pigs since 2015. Level 3 says routine biosecurity keeps it out; level 1 says it is already in the herd and there is no introduction event to prevent. On this evidence level 1 is the better reading. I have not moved it because the cell was assessed and signed off on the outbreak-control framing -- SVA appears in herds as discrete vesicular episodes that trigger foreign animal disease investigations -- and moving it would drop the entry two levels. Eric should decide, and I would recommend 1.
C4 Detection difficulty
Difficulty of recognizing and confirming infection
Laboratory-dependent: The presentation does not point to this disease specifically, but local or regional laboratories can confirm it with a validated assay once it is suspected
Corrected by Eric from L3 Reference or research laboratory required. Reason: "l2, my view is that this disease is so common in the US anymore, and they have been testing for long enough (PCR and serology), that labs have confidence in the assay. So if a local positive test for SVV and epi/history fit on the farm, the diagnosis would be made and accepted" Transcribed by the assistant and confirmed by Eric on 2026-08-31 -- "i confirm the six". The harvester refused it because the comment names two levels, but the second is a noun phrase for a level-N-capable laboratory rather than a second assignment.
Basis. ch36 36.6.8: "Laboratory testing is mandatory because the vesicular lesions caused by SVV are indistinguishable from those produced by FMDV, SVDV, VSV and VESV." A range of RT-PCR, rRT-PCR, RT-LAMP and ELISA assays are described. Hawko 2022, a dedicated review of SVA pathology and diagnostics, independently supports the level Eric ruled: detection of SVA nucleic acid by conventional and quantitative RT-PCR "is regarded as the gold-standard test for etiological diagnosis and is considered a fast, sensitive, and specific method with numerous different viral targets reported", alongside virus isolation from vesicular material, in situ hybridisation and IHC. Antibody detection runs to indirect immunofluorescence, virus neutralisation and competitive and indirect ELISAs, with VP1 indirect ELISA at 93% sensitivity and 99% specificity and VP2 at 94.2% and 89.7%. RT-LAMP, recombinase polymerase amplification with lateral flow, and insulated isothermal PCR have all been developed "for a quick and low-cost diagnosis". It also records why the clinical route does not settle it: "viral shedding is present also in animals without clinical disease with SVA-specific IgG response, suggesting that the virus may be circulating subclinically." shic_sva: "The main significance of SVA is clinical resemblance to vesicular foreign animal diseases such as foot-and-mouth disease (FMD), swine vesicular disease (SVD), and vesicular exanthema of swine (VES)." "Because vesicular diseases are clinically indistinguishable, disinfection protocols for FMD should be followed even if SVA is suspected."
How this level was decided
The assays exist and several are described, so this is not a level 4. But a vesicular lesion in a US pig is a foreign animal disease investigation until FMD is excluded, and that exclusion is made at the national reference laboratory rather than regionally. The chapter says laboratory testing is mandatory precisely because the lesion cannot be attributed clinically. Level 3. Level 2 confirmed, on Eric's correction. The new source states the reason the cell exists: SVA cannot be told from FMD, SVD or VES clinically, so a laboratory is required to say which it is -- but the assays are available and the answer comes back.
C5 Production cost
Financial impact on the infected farm's cost of production
Moderate: Losses measurably increase cost of production but remain manageable within normal farm operations, whether acute, chronic, or associated with endemic disease
Basis. ch36 36.6.6: "Clinical signs observed in the field included lameness in up to 80-90% of pigs and vesicles and erosions on the coronary bands and snouts." 36.6.6.1: "In Brazil, 20-30% mortality in neonatal piglets was recorded in farms where sows had developed SVV-associated vesicular lesions a week prior. Reports in 2014 suggested even higher mortality (30-70%) in piglets <=4 days of age... Mortality is rare in adult pigs." 36.6.6: "Lesions were resolved by 12-16 DPI."
How this level was decided
Lameness in 80 to 90% of a group, plus neonatal mortality of 20 to 30% and higher in the youngest piglets, is a measurable increase in cost of production. It stays at level 3 rather than 4 because lesions resolve in about two weeks, adult mortality is rare, and the chapter records no adverse effect on farrowing in affected sows -- the event is sharp but self-limiting. Unchanged.
C6 Market impact
Duration of material disruption to pork and pig markets
Temporary disruption: Material negative effect on supply or demand lasting less than a month when disease occurs on one or more farms
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "C6l2, this is a tricky one but the current situtation in my view is that the disease has been around long enough that people are now not particvularly worried about a diagnosis of SVV. The tricky issue is that SVV can cause vesicles, and appearance of vesicles does cause a temporary problem for a single farm when they turn up at slaughter with vesicles until the exotic causes are ruled out. The tricky distinction is are we basing the answer on appearance of vesicles or diagnosis of the disease. Vesicles causes the disruption, a diagnosis actually resolves the disruption. But I think we need to manhandle this case and not overthink it: vesicles are important and therefore it seems wrong to make this any lower than L2."
Basis. ch36 36.6.8: laboratory testing is mandatory because SVV lesions are indistinguishable from FMDV, SVDV, VSV and VESV. 36.6.4: SVV has been isolated from pigs in at least 10 US states, with an increase in vesicular disease cases concurrent with increased isolation.
How this level was decided
INFERRED. Under the standing note SCORING/market_impact, SVV is already present and routinely diagnosed in the US, and no diagnosis has produced a lasting market move -- which argues level 1. What lifts it to level 2 is the mechanism the chapter names: every SVV case presents as a possible FMD case and triggers a foreign animal disease investigation, which holds the affected premises and its movements until the rule-out comes back. That is a real disruption to the ability to move pigs, lasting days rather than months. Material effect lasting less than a month is level 2. Unchanged. Level 2: an SVA detection triggers a foreign animal disease investigation because it cannot be distinguished from FMD clinically.
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. ch36 36.6.6: "Lesions were resolved by 12-16 DPI." "Piglets that survived usually recovered in 3-10 days." 36.6.6.1: "Mortality is rare in adult pigs." No antiviral or therapeutic is described anywhere in section 36.6.
How this level was decided
No pathogen-directed treatment exists, but the second clause of level 1 holds: lesions resolve in about two weeks without intervention, surviving piglets recover in three to ten days, and adult mortality is rare. Animals recover acceptably without treatment. NOTE: this does not address the neonatal mortality, which is the real loss and which a treatment would not reach either -- the piglets die within days of birth. Unchanged.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Needed but not available: No effective vaccine is available in the US or has been developed, and the disease would justify vaccinating if one existed
Basis. ch36 36.6.10: "No commercial SVV vaccines are currently available, but an experimental vaccine based on inactivated cell culture-derived SVV has been successfully tested in pigs. Maternal antibodies from vaccinated sows protected 3- to 6-day-old suckling piglets challenged with SVV. A live-attenuated recombinant SVV vaccine candidate induced robust VN antibodies, T-cell proliferation, and protected pigs against heterologous SVV challenge."
How this level was decided
Level 3, and a clean one. No commercial vaccine exists, and the disease plainly warrants one -- neonatal mortality of 20 to 30%, lameness across most of a group, and every case triggering an FMD investigation. The chapter also shows the target is tractable: an inactivated vaccine protected suckling piglets through maternal antibody, and a live-attenuated candidate protected against heterologous challenge. Needed, achievable, and not available. This is what the reworded level 3 is for. Unchanged.
Levels and evidence are generated from data/assignments/seneca_valley_virus.yml; the overview is authored in data/overviews/seneca_valley_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.