Teschovirus asilesi (Teschovirus A)
LEVELS: Highly unlikely; No human illness; Already in the herd; Reference or research laboratory required; Minor; Temporary disruption; Little; Needed but not available
| Register id | teschovirus_a |
| Type | virus |
| Scientific name | Teschovirus asilesi |
| NCBI taxid | 3432768 |
| Evidence | 5 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Teschovirus A covers nineteen serotypes of porcine teschovirus, of which the first, the old PTV-1, is the important one: it is the agent of Teschen disease, a severe polioencephalomyelitis that historically caused paralysis and death in pigs of all ages, and of Talfan disease, its milder form. Most teschovirus infections are subclinical, and the viruses are ubiquitous — no conventional herd has ever been shown to be free of them, and even SPF repopulation and gnotobiotic derivation fail to exclude them. Besides encephalomyelitis they have been associated with reproductive failure, and the chapter's judgment is that only that reproductive syndrome is economically important enough to justify specific control in the field, though the number of serotypes involved makes vaccine development difficult. Porcine teschovirus is not WOAH-listed and no import restriction attaches to it, but because teschovirus encephalomyelitis is considered foreign to the United States it is notifiable to APHIS; restrictions on pigs and pork from endemic areas appear effective at limiting spread, and the virulent PTV-1 strains have never been isolated in North America. Vaccines have been used against Teschen disease but not against the milder forms, and a ring-vaccination eradication programme has been reported successful. Piglets with mild disease may recover with nursing care. Teschoviruses are not infectious for people.
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 36.5.3, in full: "PTVs are not infectious for humans." shic_2021_porcine_teschovirus: "PTV is not considered to be zoonotic." "Swine, including wild boar, are the only known hosts for PTV."
How this level was decided
A four-word public health section. Level 1. Level 1 confirmed twice over.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. ch36 36.5.3: "PTVs are not infectious for humans." shic_2021_porcine_teschovirus: "PTV is not considered to be zoonotic."
How this level was decided
C2 scores level 1 whenever the agent does not cause disease in people. Level 1 confirmed.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Already in the herd: Present in most herds, or carried by pigs themselves, so there is no introduction event to prevent
Basis. The 2026 Russian co-infection study reports "The overall PTV-4 seroprevalence rate in tested pigs was estimated to be 70.6%", with neutralising antibodies in 36 of the pigs tested. ch36 36.5.1: "PTVs are ubiquitous, and no conventional pig herd has been shown to be free of infection." 36.5.10 records that even SPF repopulation and gnotobiotic derivation fail to exclude them. shic_2021_porcine_teschovirus: "PTV cannot likely be excluded from farm environments. However, cleaning and disinfection protocols should be in place." "Less virulent PTVs have been found many regions." "PTV persists in the environment, surviving at moderate temperatures and pH extremes."
How this level was decided
Level 1 unchanged, with a measured seroprevalence now attached to it. 70.6% in an unselected group is the ubiquity the chapter asserts, shown rather than stated. No introduction event to prevent. Level 1 confirmed, and this is as direct a statement as the folder is likely to get: the factsheet says PTV cannot likely be excluded from farm environments. There is no introduction event to prevent.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. "l3, not all local/regional labs could confirm this diagnosis without referral"
Basis. ch36 36.5.8.1 lists virus neutralisation, complement fixation, immunofluorescence and several RT-PCR and real-time RT-PCR assays, all from research publications, and notes that serological identification requires "suitable reference reagents". 36.5.8.2: "Serology is of little value for diagnosis, unless paired sera are available and the serotype known." The 2026 study used cell culture in swine testis cells plus Cq monitoring across ten passages -- research-laboratory work. shic_2021_porcine_teschovirus: "Multiple reverse transcriptase polymerase chain reaction (RT-PCR) assays have been described targeting the 5NTR, VP1, and VP2 regions of PTV." "PTV can be grown in swine-origin cell lines and identified by virus neutralization, complement fixation, or immunofluorescence." "Enzyme-linked immunosorbent assays (ELISAs) have been developed for PTV. One was tested with oral fluids, but no anti-PTV antibodies were detected in study samples."
How this level was decided
MOVED L2 -> L3 on Eric's ruling of 2026-08-31: "l3, not all local/regional labs could confirm this diagnosis without referral." The reference-reagent requirement is the specific obstacle: serotype-level identification needs materials a diagnostic laboratory does not hold, and with nineteen types in the species that is not a detail. Level 3 held. Assays are described rather than routine, the one oral-fluid ELISA trial detected nothing, and with at least 13 serotypes and new ones frequently detected the target is moving. That is a laboratory that has to choose to look for it.
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. Flagged alongside C6 because one question governs both -- whether the entry means the endemic and largely subclinical Teschovirus A or the severe polioencephalomyelitic syndrome, given that a US Teschen outbreak occurred in 2003. Eric, 2026-09-06: "our existing assessment holds", with the reasoning recorded at teschovirus_a/market_impact. The entry is the endemic virus.
Basis. The 2026 study establishes pathogenicity cleanly in culture: "the CPE in ST was consistently evident throughout the entire cultivation period, even after the PIV5 genome was no longer detectable, thus confirming that PTV-4 induced cytopathogenicity, rather than PIV5". ch36 36.5.1: "While the majority of infections are subclinical, PTVs have been associated with a variety of clinical conditions." 36.5.10: "Only the SMEDI syndrome is of sufficient economic importance to justify specific control measures in the field." shic_2021_porcine_teschovirus: "Most infections are subclinical." "Teschen disease causes high morbidity and mortality in pigs of all ages and can result in serious economic losses. Talfan disease mainly affects younger, post-weaning pigs, and lower morbidity and mortality rates are observed." "North American outbreaks include the United States (2003), Haiti (2009), and Canada (2011)."
How this level was decided
Level 2 unchanged, now supported rather than resting on the chapter alone. The new paper adds that PTV-4 is genuinely cytopathogenic rather than an innocent passenger, which was the open question about the non-PTV-1 types -- but it is a cell-culture demonstration in a Russian co-infection case report, not a measure of field burden. The chapter still names SMEDI as the one syndrome economically important enough to warrant control measures, which is a measurable but manageable cost. NOTE: the C5 and C6 flag on this entry stands -- it spans Teschen disease and the ubiquitous mild strains, and Eric corrected C6 to L2 on 2026-08-29 with "it would depend on the scale of the outbreak so we go with L2 for now". Level 2 held, and the range is worth recording because it is wide. The registered entry is Teschovirus A as a whole, and the typical situation for it is subclinical circulation or the milder Talfan picture; Teschen disease is the severe outlier and the general rule directs scoring the typical entry rather than the most severe variant. NOTE FOR ERIC: a US Teschen outbreak did occur in 2003, so this is not purely hypothetical, and if he reads the entry as covering that syndrome it is a 3 or 4.
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
INFERRED — reasoned, not stated. The evidence implies this level rather than stating it. The reasoning is below.
Corrected by Eric from L1 Negligible. Reason: "C6L2, my feeling is Tescho A is a special case of enteroviruses and there would be a market impact so L1 is clearly not correct. The question is more around L2 or L3, and I don't think we know ahead of time, it would depend on the scale of the outbreak so we go with L2 for now. I do wonder if it would go teh way of the 2013 PEDV incursion where essentially spread was too far by the time the diagnosis was made and therefore the government and industry elected not to respond." RE-CONFIRMED 2026-09-06 after the SHIC factsheet was placed. The factsheet records that teschovirus encephalomyelitis is notifiable to APHIS as a foreign disease, which was put to him as a possible argument for moving the cell. Eric: "leave tescho A as it stands. personally, i think the 'tescho' term is antiquated though it still languishes in the aphis and woah literature. Enteroviruses are everywhere. we now know how aphis will respond and our existing assessment holds." TWO ARGUMENTS THERE, both about the register entry rather than the paperwork: the notifiable category is a historical artefact attached to an antiquated name, and porcine enteroviruses are ubiquitous, so a detection is not the exceptional event the listing implies. The last clause -- we now know how APHIS will respond -- is the market test applied to observed recent experience rather than to the listing, and it is the same reasoning as his 2013 PEDV analogy above.
Basis. ch36 36.5.8: "Teschen disease (also known as teschovirus encephalomyelitis) is designated as a WOAH notifiable disease." 36.5.10: "Restrictions on the import of swine and pork products from areas in which Teschen disease is endemic seem to be effective in limiting the spread of virulent PTV-1 strains." 36.5.4: "The virulent PTV-1 strains associated with classical Teschen disease... have not been isolated in North America." shic_2021_porcine_teschovirus: "PTV is not currently an OIE-listed disease. There are no restrictions for importation of animals from countries or zones affected by PTV. However, teschovirus encephalomyelitis is considered foreign to the United States, and is therefore notifiable according to the U.S. Animal and Plant Health Inspection Service (APHIS)."
How this level was decided
INFERRED, AND FLAGGED as the same split that runs through C5. Under the standing note SCORING/market_impact, teschoviruses are already endemic in every US herd and routinely diagnosed with no market response, which returns level 1. But Teschen disease is WOAH-notifiable and the chapter records import restrictions used against it, so a virulent PTV-1 incursion would be a trade event of some length. Level 1 scores the entry as it exists in the US. Eric may prefer it scored on the notifiable form. LEVEL 2 STANDS, on Eric's ruling of 2026-08-29 -- "C6L2, my feeling is Tescho A is a special case of enteroviruses and there would be a market impact so L1 is clearly not correct" -- re-confirmed by him on 2026-09-06. The new factsheet was flagged to him because it records that teschovirus encephalomyelitis is NOTIFIABLE to APHIS as a foreign disease, which looked like an argument to go higher still. He declined: "the 'tescho' term is antiquated though it still languishes in the aphis and woah literature. Enteroviruses are everywhere. we now know how aphis will respond and our existing assessment holds." CORRECTION TO THIS PASS: the re-assessment first described this cell as sitting at level 1 and asked whether notifiability should lift it. It was already at 2, on his ruling -- the pass had read the stored level instead of the resolved one.
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 36.5.10: "As with most viral infections, control measures for PTV depend on prevention rather than treatment. Potential antiviral chemotherapeutics for porcine enteric picornaviruses have received little attention. Piglets with mild polioencephalomyelitis may recover if nursing care is provided during the period of transient paresis." 36.5.1: "the majority of infections are subclinical". shic_2021_porcine_teschovirus: "There is no treatment for pigs infected with PTV."
How this level was decided
No pathogen-directed treatment exists and none is being sought, which read alone points at level 3. The second clause of level 1 settles it instead: the majority of infections are subclinical, and piglets with the mild form recover with nursing care through a transient paresis. Animals recover acceptably without treatment. NOTE: nursing care is supportive, not pathogen-directed, so it is the recovery rather than the care that carries the level. Level 1 held.
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 36.5.10: "Only the SMEDI syndrome is of sufficient economic importance to justify specific control measures in the field, but the multiplicity of serotypes that may be involved complicates the development of an effective vaccine." "Vaccination has been practiced in the field for the control of Teschen disease but not against the milder forms... The earlier Teschen disease vaccines containing inactivated virus of pig tissue origin have been superseded by attenuated or inactivated cell culture vaccines. Success was claimed for a Teschen disease eradication program involving ring vaccination and slaughter." shic_2021_porcine_teschovirus: "Both live and attenuated vaccines were used during European outbreaks of Teschen disease but are no longer commercially available." "Cross-protection between PTV strains is unlikely." "no PTV vaccines are currently available." "Maternal antibodies are protective against PTV-induced reproductive disorders."
How this level was decided
Level 3, and one of the few genuine ones in this batch -- the chapter states both halves of the reworded test in a single sentence. SMEDI is economically important enough to justify control measures, which is the disease warranting a vaccine, AND the multiplicity of serotypes complicates developing an effective one, which is why there is not one. Needed but not available, word for word. The Teschen vaccines that exist are for a disease absent from North America and do not address the syndrome that matters here. Level 3 confirmed, and this is now one of the best-evidenced level 3 cells in the register. The standing note reserves level 3 for a DEMONSTRATED gap, and the shape here is stronger than the streptococcus_zooepidemicus example it cites: vaccines against Teschen disease existed, were used in European outbreaks, and were withdrawn commercially. The product is not merely absent, it has been taken away, and maternal antibody data show the target is immunologically tractable.
Levels and evidence are generated from data/assignments/teschovirus_a.yml; the overview is authored in data/overviews/teschovirus_a.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.