Atypical Porcine Pestivirus
LEVELS: Highly unlikely; No human illness; Already in the herd; Laboratory-dependent; Minor; Negligible; Little; Available, or not needed
| Register id | atypical_porcine_pestivirus |
| Type | virus |
| Scientific name | atypical porcine pestivirus |
| NCBI taxid | 1914447 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Atypical porcine pestivirus was found in the United States during a metagenomic sequencing project aimed at something else, and has since been detected on every continent except Africa and Antarctica, in domestic pigs and wild boar, in at least seventeen countries — including in surveys of perfectly healthy animals. It establishes a chronic persistent infection, with RNA still detectable in oral fluid and semen long after exposure. The only disease ever linked to it is congenital tremor in newborn piglets, the shaking condition sometimes called dancing pig disease, and the link is supported by both field observation and experimental work. But clinical disease is rare, no illness has been seen in weaned pigs or sows, and what determines whether an infected litter shakes or not is unknown. Because it was recognised so recently and its significance on commercial farms is undetermined, no prevention or control strategies have been described. Detection relies on PCR assays developed after the original sequencing; a multiplex microarray now tests for African swine fever, classical swine fever and APPV together. There is no commercial vaccine, though experimental virus-like particle and subunit candidates have been described. Pestiviruses do not infect 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. ch35 35.1.1, which is the whole of the chapter's public health section and covers every entry in this batch: "There is no evidence of human infection with pestivirus, and they are not of any significance for public health or food safety." shic_2011_appv: "There is no evidence that pestiviruses, including APPV, are zoonotic."
How this level was decided
Level 1, stated outright for the whole genus. The SHIC factsheet confirms level 1 in one line and adds nothing that disturbs it.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. ch35 35.1.1, which is the whole of the chapter's public health section and covers every entry in this batch: "There is no evidence of human infection with pestivirus, and they are not of any significance for public health or food safety." shic_2011_appv: "There is no evidence that pestiviruses, including APPV, are zoonotic." "APPV infects only swine (domestic and wild)."
How this level was decided
Level 1. No human infection with pestiviruses is on record. Confirmed. The host-range statement is the stronger of the two for C2 under the 2026-09-04 separation: an agent that infects only swine causes no human illness.
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. ch35 35.5.1: APPV "was detected in the USA during a PRRSV metagenomic sequencing project. Subsequently, this virus was detected in all continents except Africa and Antarctica and in both domestic pigs and in wild boar." 35.5.3 lists detection in seventeen named countries including the United States, and "Investigations of 1460 serum samples of HEALTHY pigs from different parts of Europe and Asia demonstrated a geographically wide distribution of APPV." 35.5.4: "Cumulatively these studies suggest that APPV causes a chronic persistent infection in pigs" -- RNA still detectable in oral fluid, semen and multiple tissues at 6 to 11 months of age. 35.1: "APPV is widespread in the global pig population." shic_2011_appv: "APPV is widely distributed", "APPV likely occurs worldwide", identified in the United States in 2015. "APPV can circulate for years on an affected farm, despite testing and removal of infected animals." Recommended management is "acclimatization of replacement gilts to ensure APPV exposure before breeding".
How this level was decided
Level 1. This is the biome case that level 1 was written for: the virus is in healthy pigs on every continent that has pigs, it was found in the United States by accident while somebody sequenced for something else, and it establishes a chronic persistent infection that carries pigs through to market age. There is no introduction event to prevent because it is already here and already in them. Transmission runs horizontally, transplacentally and through semen, which closes the remaining routes. Level 1 confirmed, and now supported rather than inferred. The factsheet's control advice is the clinching detail: the recommendation is to EXPOSE incoming gilts to the virus deliberately, which is only coherent for an agent already in the herd.
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
Basis. ch35 35.5.7: "APPV was first detected by next-generation nucleic acid sequencing technology. This provided an insight into the virus genome and supported the development of APPV-specific rRT-PCR assays." A crystal digital RT-PCR, multiplex real-time RT-PCR and a multiplex gene microarray for simultaneous detection of African swine fever virus, CSFV and APPV are described, together with indirect and blocking ELISAs, a virus neutralisation test, virus isolation on PK-15 and SK-L cells, IHC and in situ hybridisation. 35.5.2: "APPV has been suggested as a cause of congenital tremor type A-II although other potential causative agents cannot be ruled out." shic_2011_appv: "both conventional and qRT-PCR assays have been developed", targeting NS2/3, NS5A/B or both, plus Erns and E2 assays; ELISAs based on NS3, E2 and Erns; immunofluorescence, immunohistochemistry and in situ hybridization; a multiplex RT-PCR for ASFV, CSFV and APPV. "Preferred samples for CT include CNS, lymph nodes, and serum. APPV can be detected in oral fluids."
How this level was decided
Level 2. The toolkit is unusually complete for a virus recognised in 2015 -- specific rRT-PCR, two ELISA formats, a neutralisation test, isolation, IHC and ISH -- and it is validated and multiplexed alongside ASFV and CSFV, so it is available at regional level. What rules out level 1 is attribution rather than technique: congenital tremor is a syndrome with five recognised type A causes, APPV is only "suggested" as the cause of type A-II, and the chapter says other agents cannot be ruled out. Finding APPV in a trembling piglet does not by itself make the diagnosis, since the virus is also in healthy pigs everywhere. Level 2 confirmed and considerably better evidenced. Multiple assay families are in routine use including a multiplex run alongside ASFV and CSFV, so this is well past the unvalidated-assay level 4, and it is ordinary laboratory work rather than reference-laboratory work.
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. ch35 35.5.1: "Field observations and experimental studies suggest that atypical porcine pestivirus is associated with congenital tremors. Its clinical relevance remains to be defined, although present evidence suggests it to cause sporadic disease." 35.1: "clinical APPV is rather rare and the factors leading to clinical manifestations remain unclear." 35.5.5: "The only clinical entity with which APPV has been associated is the congenital tremor syndrome observed in new-born piglets. No disease has been observed in weaning age pigs or sows." In experiments the within-litter proportion affected ran from 57 to 100% and 0 to 100%, with 0-40% additionally showing splayleg. 35.5.3: "During congenital tremor outbreaks induced by APPV, piglets born to primiparous sows are predominantly affected, whereas those born to multiparous sows typically remain unaffected." shic_2011_appv: "APPV is widely distributed, but its clinical relevance is poorly understood. To date, APPV has been associated only with congenital tremors in newborn pigs." "In litters with CT, morbidity ranges from 0-100%." "Litters from primiparous sows (gilts) are most commonly affected." "In one study of APPV-seropositive sows, clinical signs were not observed in suckling pigs."
How this level was decided
Level 2. When an outbreak happens it is concentrated and expensive -- most or all of a gilt litter shaking, some with splayleg, and piglets that cannot nurse well are piglets that die -- but the chapter is consistent that clinical disease is sporadic and rare against a background of near-universal infection, and that it burns out as parity rises because multiparous sows protect their litters. Small and generally short-lived losses falling on the gilt cohort. Level 2. Level 2 confirmed. The factsheet holds the range in view -- morbidity within an affected litter can reach 100%, but the syndrome is confined to gilt litters, seropositive sows produced unaffected pigs, and the only disease attributed to the virus in a decade is congenital tremor. Losses are real and short-lived rather than a standing cost, which is the level 2 test.
C6 Market impact
Duration of material disruption to pork and pig markets
Negligible: Little or no material disruption to supply or demand when disease occurs on one or more farms
Basis. ch35 35.5.1 and 35.5.3: APPV has been detected in the United States since 2015 and in seventeen named countries across every continent except Africa and Antarctica, in domestic pigs and wild boar, including in surveys of healthy animals. No trade measure, movement control or consumer response is recorded anywhere in section 35.5. shic_2011_appv: "APPV is not an OIE-listed disease. There are no restrictions for importation of animals from countries or zones affected by APPV."
How this level was decided
Level 1 under the standing note SCORING/market_impact in its original form -- an agent long present and routinely diagnosed in US pigs with no historical market move. There is a decade of observed precedent across seventeen countries, which is as much as this criterion ever gets. Level 1, and this moves the cell from inference to a direct statement: the factsheet says in terms that no import restriction attaches to the virus anywhere.
C7 Treatment potential
Potential for treatment to improve outcomes
Little: Effective pathogen-directed treatment is available and works, or animals recover acceptably without it
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c7l1, there seems to be little opportunity to treat affected piglets and no opportunity to treat the sow - this seems to be a herd startup or gilt problem that is typically being managed by purposeful dam exposure."
Basis. Chapter 35 describes no treatment for APPV. 35.5.9: "Strategies for the prevention and control of APPV have not been described because the presence of APPV in swine was recognized relatively recently and its clinical significance in commercial swine farms has not been determined." 35.5.5: "No disease has been observed in weaning age pigs or sows." shic_2011_appv: "There is no treatment for APPV infection in swine." Control is "acclimatization of replacement gilts... feedback in farms with clinical CT cases". "Vertical transmission is associated with the development of CT."
How this level was decided
INFERRED. No treatment exists and the chapter says outright that control strategies have not been described. Under the standing note SCORING/treatment_potential this is level 1 on the no-imperative clause: the only clinical entity is a congenital tremor present from birth, so the damage is transplacental and complete before a piglet could be treated, and the pigs that could be treated -- weaners and sows -- do not get ill. FLAGGED as the softest cell in this entry, since the chapter states the clinical significance is undetermined rather than absent. Level 1 confirmed on the boundary the standing note draws explicitly for the pestiviruses: level 1 holds where the harm is transplacental and complete before birth, because no treatment could act in time. A piglet is born with hypomyelination already established. The absence of a product is not the reason for the level.
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. "c8l1, not that significant of a problem in US to warrant development of a vaccine, problem that is typically being managed by purposeful dam exposure, does not seem to be a persistent problem for farms"
Basis. ch35 35.5.9: "There are currently no commercial vaccines for APPV but several experimental vaccines have been described. These include a vaccine based on virus-like particles of APPV and a subunit vaccine based on E2 protein of APPV that reportedly induced strong APPV antibody responses in immunized mice. A Fc-mediated E2-dimer subunit vaccine of APPV was shown to induce efficient humoral and cellular immune responses in piglets." 35.1: "clinical APPV is rather rare." shic_2011_appv: "There is no commercial vaccine for APPV." Control is "acclimatization of replacement gilts to ensure APPV exposure before breeding" and "feedback in farms with clinical CT cases, until an effective commercial vaccine is available."
How this level was decided
INFERRED. No commercial vaccine exists, and under the reworded criterion the question is whether one is warranted. Scored level 1 because clinical APPV is rare against near-universal infection, no disease occurs in weaners or sows, and the chapter says the clinical significance in commercial farms has not been determined -- a gap cannot be established for a burden that has not been measured. FLAGGED, AND THE ARGUMENT AGAINST IS ON THE PAGE: three experimental vaccines have been built and one works in piglets, which is a lot of effort for something nobody needs. If Eric reads that as evidence the field thinks a vaccine IS warranted, this is level 3. Level 1 confirmed, and it is Eric's own ruling on this entry that governs -- the standing note records it under the third route to no imperative, a problem "typically being MANAGED BY PURPOSEFUL DAM EXPOSURE". The factsheet documents exactly that practice. NOTE THE TENSION, which is his to weigh if he ever revisits it: the factsheet's own phrasing is "until an effective commercial vaccine is available", which reads as an expectation that one is wanted.
Levels and evidence are generated from data/assignments/atypical_porcine_pestivirus.yml; the overview is authored in data/overviews/atypical_porcine_pestivirus.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.