Classical Swine Fever Virus
LEVELS: Highly unlikely; No human illness; Extraordinary biosecurity required; Reference or research laboratory required; Substantial; Prolonged disruption; Little; Available, or not needed
| Register id | classical_swine_fever_virus |
| Type | virus |
| Scientific name | Classical swine fever virus |
| NCBI taxid | 11096 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Classical swine fever, historically called hog cholera, is a pestivirus disease of pigs and wild boar with no other host. Virulent strains cause a haemorrhagic disease with high fever, huddling, skin discolouration, neurological signs and mortality that can approach 100% — clinically very similar to African swine fever, which is why the two must be separated in the laboratory. Less virulent strains cause a chronic or mild disease that is easy to miss, and infection of a pregnant sow with a moderately virulent strain can produce persistently infected piglets that appear healthy while shedding virus for months, which is the single most dangerous way the disease hides in a population. It spreads by contact, in pork products and by feeding uncooked waste. The United States has been free of it since 1978, and it remains a notifiable disease whose confirmation would close export markets immediately. Effective vaccines exist and are used in endemic regions, including marker vaccines that allow vaccinated animals to be distinguished from infected ones, but vaccination is incompatible with the disease-free status most exporting countries hold, so control in a free country means exclusion, rapid detection and stamping out.
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."
How this level was decided
Level 1, stated outright for the whole genus. This is an examined negative rather than a silence -- chapter 35 gives the question its own section and disposes of it in one sentence covering all six pestivirus entries in this batch.
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."
How this level was decided
Level 1. C2 grades illness acquired from pigs and the chapter says there is no human infection with pestiviruses at all.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c3l5, agree with assessment - the germany example is the exception rather than the rule. In general, diseases in wild pigs are likely to continue to circulate in wild pigs unless all are depopulated. Japan example is much more representative" RESCALED 2026-09-03, when C3 went from five levels to four and level 4 absorbed level 5. A ruling of his is never overturned by a scale change, so what is recorded here is the same judgment expressed on the new scale. AND THE ENTRY ALSO MOVED, on the pass Eric approved the same day: the whole old level 5 block was re-read against the exclusion test rather than the reservoir test, because twenty-one of those entries had been renumbered past the housing level on 2026-09-01 without being judged against it. See the entry justification for the reason this one moved. Recorded on the old scale as level 5, from_level 5.
Basis. ch35 35.2.9.1: "Wild boar can serve as a reservoir of CSFV and outbreaks in domestic pigs are often attributed to transmission from wild boar (52% according to Fritzemeier et al. 2000)." 35.2.3: "CSFV has a narrow host range restricted to domestic pigs, wild boar and other members of the family Suidae." "In September 2018, CSFV reemerged in Japan after 26 years affecting both domestic pigs and wild boars, and vaccination of both the domestic and wild boar (via oral bait) population was initiated in 2019." 35.2.2: in liquid manure CSFV survives 2 weeks at 20 C and more than 6 weeks at 4 C. 35.2.5: persistently infected carrier pigs "shed high levels of virus for several months and are important virus reservoirs" while lacking antibody, which "complicates CSFV detection and control".
How this level was decided
RENUMBERED L5 -> L4 on 2026-09-03, when C3 was reduced from five levels to four and level 4 absorbed level 5. THE JUDGMENT IS UNCHANGED and this one really is a renumber: the merged level 4 label carries what level 5 said, ending "and may still fail". IT WAS STILL CHECKED rather than assumed, because the last renumber on 2026-09-01 was mechanical and moved twenty-one entries past a level they should have been judged against. The check is the exclusion test -- does housing close the route? For this entry it does not.
EARLIER REASONING, kept because it is the evidence read: Level 5. The reservoir that decides it is feral swine, which the US has in the millions, and the European experience is that just over half of domestic outbreaks are attributed to wild boar. Japan is the live demonstration: CSF returned in 2018 after 26 years free, established in wild boar, and oral bait vaccination of the wild population has been running since 2019 rather than ending it. FLAGGED, AND IT IS A REAL COUNTER-ARGUMENT: unlike African swine fever, CSFV HAS been eradicated from wild boar populations -- Germany cleared its 2009 outbreak within months with three double vaccination campaigns a year, and the chapter says CSFV in wild boar "can be confined to a defined area until it is eliminated". If Eric reads that as the reservoir being removable, this is level 4 rather than 5. Scored level 5 because removing it takes a multi-year national wildlife vaccination programme, which is neither a farm action nor an industry one.
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. ch35 35.2.7: "Because CSFV infection produces no pathognomonic clinical signs, laboratory diagnosis is essential and, since CSFV, BVDV, and BDV share common antigens, it is critical to discriminate among them." Moderately virulent strains "are particularly difficult to diagnose under field conditions and can be mistaken for many other diseases including porcine reproductive and respiratory syndrome, the postweaning dermatitis and nephropathy syndrome, salmonella infection, coumarin poisoning, or African swine fever." 35.2.7.2: "The virus neutralization test (VNT) has been considered the reference assay... requires good quality serum samples and the use of infectious CSFV and a cell culture system... 3-5 days to obtain results." Samples are tested against BVDV and BDV reference strains in parallel and a threefold titre difference is needed to call it.
How this level was decided
Level 3, the framework's worked example at that level. Excellent validated assays exist -- rRT-PCR is the assay of choice with commercial kits, and the chapter is emphatic about its sensitivity -- so this is not level 4. What puts it at level 3 is where the work has to happen: CSF is a WOAH-listed foreign animal disease, so a US suspicion goes to the national reference laboratory by regulation, and the confirmatory serology requires infectious CSFV, cell culture and parallel titration against two ruminant pestiviruses to resolve cross-reaction. Note also that the clinical picture actively misleads -- the chapter lists African swine fever among the diseases it is mistaken for.
C5 Production cost
Financial impact on the infected farm's cost of production
Substantial: Severe losses cause a major and potentially unsustainable increase in cost of production
Basis. CFSPH 2025: "Highly virulent strains of CSFV, which were prevalent at one time, have morbidity and mortality rates that can approach 100% in a naive herd. However, most outbreaks are now caused by moderately virulent strains... Some moderately virulent strains have caused only 20% mortality in experimentally infected pigs." ch35 35.2.9: "control is based on early detection and stamping out of infected or suspect herds, with the implementation of concomitant quarantine measures." "In certain situations, such as the 1997 outbreak in the Netherlands, movement restrictions that prevented the movement of pigs to slaughter resulted in the unnecessary euthanasia of large numbers of animals."
How this level was decided
Level 4. Scored under the standing note SCORING/production_cost_impact on what an incursion into modern US production would cost, and the answer is not the mortality rate -- it is the response. CSF is controlled by stamping out infected and suspect herds under movement restriction, so an affected unit loses its whole inventory whatever the strain's virulence, and the Netherlands 1997 precedent shows the restrictions themselves forcing the destruction of healthy pigs that could not move to slaughter. That is a major and potentially unsustainable increase in cost of production, which is the level 4 test, and it is the same shape as African swine fever, the level 4 worked example.
C6 Market impact
Duration of material disruption to pork and pig markets
Prolonged disruption: Material negative effect on supply or demand lasting more than 6 months when disease occurs on one or more farms
Basis. ch35 35.2.1: CSF is "one of the World Organisation for Animal Health (WOAH)-listed diseases". 35.2.9: "For purposes of international trade, free areas maintain a no vaccination policy against CSFV... While the use of vaccine has economic consequences (i.e. vaccinated areas are banned from international trade for at least 1 year), emergency vaccination in the face of an outbreak is more likely to be considered in the future." 35.2.3: Japan lost its free status in September 2018 and was still vaccinating wild boar from 2019 onward.
How this level was decided
Level 4. There is abundant precedent, which is what the standing note SCORING/market_impact requires: the Netherlands 1997 epidemic, the Japanese re-emergence of 2018, and the WOAH free-status framework itself. The duration is stated in the chapter rather than estimated -- choosing to vaccinate costs at least a year of international trade, and Japan has not recovered its free status years on. Material disruption lasting more than six months is level 4.
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, clinical expression can vary based on virus strain and other factors, there is not an obvious reason to invest in treatment as response to infection in the US will be to eradicate."
Basis. Chapter 35 describes no treatment for CSF anywhere. Control is "early detection and stamping out of infected or suspect herds" (35.2.9), supported by vaccination. 35.2.3: North America is currently free of CSFV.
How this level was decided
INFERRED. Under the standing note SCORING/treatment_potential, level 1 covers the case where there is no imperative to treat, and it arises here in its starkest form: the regulatory response to a CSF-positive pig is depopulation, so a treatment would never be used even if one existed. The agent is also absent from the US and excludable, which is the ground on which Eric ruled Trichinella level 1. FLAGGED because the shape is unusual -- these animals do not recover acceptably without treatment, they are killed, and level 1 is reached by the criterion having no purchase rather than by the disease being mild.
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
Basis. ch35 35.2.9: "Various CSFV vaccines are available, including the modified live Chinese C strain, the Thiverval strain, and newer marker vaccines that allow for the differentiation of field virus-infected from vaccinated animals." "Traditional modified live virus (MLV) vaccines induce fast protection against clinical disease, even by the oral route... The duration of immunity is at least 6-10 months." "The chimeric pestivirus CP7-E2Alf has been licensed after being widely assessed for its safety and potency... shown to induce a high level of immunity and protection, regardless of the route of inoculation, to prevent further virus spread, and to be safe in growing pigs and pregnant sows."
How this level was decided
Level 1, the framework's worked example at that level, and it reads on the first clause of the reworded criterion -- effective vaccines secured for national outbreak response. Multiple licensed products exist including a DIVA marker vaccine that protects by either route and is safe in pregnant sows. The US does not vaccinate, but that is a trade policy decision rather than an absence: free areas maintain a no-vaccination policy precisely because the products would cost them their status. NOTE the limitation the chapter records, which does not change the level: two doses of E2 marker vaccine protected pregnant gilts from clinical disease but did not prevent transplacental infection, so vaccination cannot prevent the carrier sow syndrome.
Levels and evidence are generated from data/assignments/classical_swine_fever_virus.yml; the overview is authored in data/overviews/classical_swine_fever_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.