Porcine Circovirus 2
LEVELS: Highly unlikely; No human illness; Already in the herd; Laboratory-dependent; Moderate; Negligible; Little; Available, or not needed
| Register id | porcine_circovirus_2 |
| Type | virus |
| Scientific name | Porcine circovirus 2 |
| NCBI taxid | 85708 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-06, against criteria version 093366e352a2 |
Overview
Porcine circovirus 2 is a very small DNA virus that is present in essentially every pig population in the world. Most infections cause nothing at all, but PCV2 can produce a group of conditions collectively called porcine circovirus disease: a wasting, immunosuppressive systemic disease that typically hits pigs at two to four months of age and depletes their lymphoid tissue; reproductive failure; and porcine dermatitis and nephropathy syndrome, a striking skin and kidney condition. Before vaccines became available in 2007 this was one of the most damaging diseases in modern pig production, causing 4-20% mortality on affected farms as well as slower growth. Commercial vaccines changed that decisively, and they remain among the most widely used products in the industry — they suppress both the clinical disease and the subclinical growth loss that is easy to overlook. PCV2 has not gone away: it still circulates almost everywhere, and its main role now is as a partner in mixed infections, worsening whatever else the pig is carrying, particularly PRRSV and the respiratory bacteria.
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. ch27 27.3, the whole Public Health section for the chapter: "PCVS ARE NOT ZOONOTIC. PCV DNA has been detected in vaccines produced for use in humans and swine. THESE FINDINGS REFLECT QUALITY CONTROL ISSUES IN VACCINE PRODUCTION. PCV2 AND PCV3 HAVE BEEN DETECTED IN OTHER SPECIES BESIDES SUIDS, BUT NOT IN HUMANS." 27.4 lists the non-suid species PCV2 genome has been found in -- warthogs, peccaries, calves, antelopes, dogs, mink, fox, raccoon dogs and jackals -- and stresses that "PCV DETECTION IN THESE SPECIES IS EXTREMELY SPORADIC and the demonstration of a productive infection, as opposed to contamination or passive exposure, is challenging". People are on none of those lists. shic_2026_pcv3: "Porcine circoviruses (PCVs), including PCV3, are not considered to be zoonotic."
How this level was decided
Level 1, and this entry is the framework's worked example there. The chapter answers the question in three words and then does the thing that makes the answer credible: it lists nine non-porcine species in which PCV2 DNA has been found, and humans are not among them despite PCV2 being ubiquitous in pigs worldwide for thirty years. NOTE THE ONE HUMAN CONNECTION AND WHY IT IS NOT ZOONOSIS: PCV DNA turned up in vaccines made for people, which the chapter attributes to quality control in vaccine production rather than to infection. Contamination of a manufacturing line is not transmission from a pig. Level 1 confirmed for the genus.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. ch27 27.3, the whole Public Health section for the chapter: "PCVS ARE NOT ZOONOTIC. PCV DNA has been detected in vaccines produced for use in humans and swine. THESE FINDINGS REFLECT QUALITY CONTROL ISSUES IN VACCINE PRODUCTION. PCV2 AND PCV3 HAVE BEEN DETECTED IN OTHER SPECIES BESIDES SUIDS, BUT NOT IN HUMANS." shic_2026_pcv3: "Porcine circoviruses (PCVs) ... are not considered to be zoonotic."
How this level was decided
Level 1. Under C2 as rescoped, level 1 means pigs are not a source of human illness with this agent, and the chapter says the genus does not infect people at all. C1L1 implies C2L1 and validate_criteria.py checks it. 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. ch27 27.5.1: "SINCE PCV2 IS UBIQUITOUS, IT IS RELATIVELY SAFE TO ASSUME THAT MOST FARMS HAVE PIGS WITH SUBCLINICAL PCV2 INFECTIONS." 27.4: "Based on retrospective studies and bioinformatic analysis, PCVS CIRCULATED UNDETECTED IN SWINE FOR DECADES OR EVEN CENTURIES", and "most pigs became infected between 4 and 11 weeks of age, depending on the farm". The virus is shed in "nasal, tonsillar, bronchial, and ocular secretions, feces, saliva, urine, colostrum, milk, and semen", passes transplacentally, and "a variable percentage of sows and piglets may be viremic during lactation". 27.2.3: PCV2 "resists inactivation at 56 C for 1 hour and 75 C for 15 minutes, which suggests that the virus remains infectious in the environment at high ambient temperatures". PCV1, PCV2 and PCV3 "are commonly detected in feral swine, often at high prevalence". shic_2026_pcv3: "In 1997, PCV2 was recognized as the cause of a novel wasting disease affecting Canadian pigs." "Evidence suggests that PCVs have been circulating in swine long before they were first detected." "Circoviruses are stable in the environment."
How this level was decided
Level 1, and the chapter states the level 1 label in its own sentence: PCV2 is ubiquitous and most farms have subclinically infected pigs. There is no introduction event to prevent. Every other fact points the same way -- the virus has been in pigs for decades or centuries undetected, it is shed by every route including colostrum and semen, it crosses the placenta, and it resists 75 degrees for a quarter of an hour. NOTE THAT NOTHING IN THE PREVENTION SECTION PROPOSES EXCLUDING IT: control is vaccination and the management of cofactors, which is what a farm does about an agent it already has. Level 1 confirmed.
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. ch27 27.5.2.4: "NEITHER CLINICAL SIGNS NOR GROSS LESIONS observed in suspected PCV2-SD-affected pigs ARE SUFFICIENT TO DIAGNOSE THE DISEASE. In particular, the respiratory form of PRRSV infection and ALL DISEASES AND CONDITIONS THAT CAUSE WASTING must be differentiated." The case definition needs three things together: wasting with dyspnoea and enlarged inguinal nodes; moderate-to-severe characteristic lymphoid histopathology; and moderate-to-high PCV2 concentration within those lesions. On the assays: "IN SITU HYBRIDIZATION (ISH) AND IMMUNOHISTOCHEMISTRY (IHC) ARE WIDELY USED for the diagnosis of PCV2-SD", and "one of the most widely used techniques is REAL-TIME QUANTITATIVE PCR (qPCR)... applied to other sample types including oral fluids, placental umbilical cords, processing fluids or tissues, and environmental samples, thereby providing a useful monitoring strategy". Two limits: "qPCR ALONE IS INSUFFICIENT TO DIAGNOSE PCV2-SD and it must be coupled with clinical signs and histopathological data", and "diagnosis of PCV2-SD using serological techniques is problematic BECAUSE PCV2 IS UBIQUITOUS and seroconversion patterns are similar in affected and non-affected farms".
How this level was decided
Level 2, on both halves of the label. The presentation does not point here -- wasting is the least specific sign in a nursery and the chapter sends the diagnostician through PRRSV and everything else that wastes a pig first -- but validated assays run in ordinary diagnostic laboratories: qPCR on serum, tissue, oral fluids and processing fluids, plus ISH and IHC, all described as widely used. NOTE THE INTERPRETIVE RULE THAT DEFINES THIS ENTRY, because it is a limit on reading the result rather than on getting one: because the virus is on every farm, a positive means nothing by itself. WHAT SEPARATES DISEASE FROM SUBCLINICAL INFECTION IS THE AMOUNT, not the presence, and the amount has to be seen inside the lesion. That is also why serology is useless here. Unchanged. The factsheet is about PCV3 and uses PCV2 as its comparator; it adds nothing on PCV2 diagnostics.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c5l3, effect quite variable across farms and presentation, with variable help from vaccination"
Basis. ch27 27.5.2.2: in PCV2-systemic disease, "MORBIDITY IN AFFECTED FARMS IS COMMONLY 4-30% (OCCASIONALLY 50-60%) AND MORTALITY IS 4-20%", characterised by wasting, pallor, respiratory distress and diarrhoea, typically at 2-4 months of age. 27.5.4.2 on the dermatitis and nephropathy syndrome: prevalence is usually under 1% but "MORTALITY APPROACHES 100% IN PIGS OLDER THAN 3 MONTHS versus approximately 50% in younger pigs". 27.5.1 on the subclinical form, which is the one most farms have: it is "characterized by LOWER AVERAGE DAILY GAIN in the absence of overt clinical signs", and "fully PCV2-vaccinated pigs GAINED 10-40 G PER DAY MORE than unvaccinated pigs". 27.1: "Commercial PCV2 vaccines have been available since 2007 and ECONOMIC LOSSES ATTRIBUTED TO PCVDS, INCLUDING SUBCLINICAL PCV2 INFECTIONS, HAVE BEEN MARKEDLY REDUCED." shic_2026_pcv3: PCV2 is described as "a major swine pathogen", and PCV3 is assessed throughout by comparison with it. "PCV2 prevention is based on factors that can influence susceptibility. These include good nutrition, biosecurity, and vaccination."
How this level was decided
Level 3, and FLAGGED AS A LEVEL 3 OR 4 JUDGMENT because the answer depends on whether the criterion scores the disease or the disease as it is now managed. Level 3 is scored under the standing note SCORING/production_cost_impact, which says to score against modern US production: PCV2 vaccination is near-universal, the chapter says losses have been markedly reduced since 2007, and what remains is a continuous tax -- the cost of vaccinating every pig, plus 10 to 40 grams a day of gain in anything unvaccinated, plus occasional breaks. Losses that measurably increase cost of production but remain manageable within normal operations. THE ARGUMENT FOR LEVEL 4 is what the numbers say without the vaccine: 4 to 20% mortality with morbidity up to 60% is unsustainable, and the reason the industry vaccinates universally is that it was. This is the same shape as the pseudorabies C5 question, where the pass scored level 4 because the US is free and every herd is naive; here the US is not free and every herd is vaccinated. Level 3 held. The factsheet's framing is useful corroboration -- PCV2 is the reference point against which an emerging circovirus is judged important -- but it is placed here thin and adds no new figures.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c6l1, no effect on market, very old disease"
Basis. PCV2 is ubiquitous in pigs worldwide and has been for decades. No trade measure, movement control or consumer response is recorded anywhere in chapter 27.
How this level was decided
INFERRED. Under the standing note SCORING/market_impact, an agent present on essentially every US farm and diagnosed continuously since the late 1990s, with no market move on record, is level 1. There is a long precedent here rather than a void: PCV2-systemic disease was an epidemic in North America and Europe around 2000 and the pork market did not move. Unchanged.
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. No antiviral or pathogen-directed treatment for PCV2 is described anywhere in chapter 27. 27.7 gives the control approach instead: "PCV2-SD is a multifactorial disease THAT CAN BE CONTROLLED BY THE USE OF PCV2 VACCINES", and before vaccines existed control depended on managing cofactors through Madec's 20-point plan. 27.1: "economic losses attributed to PCVDs, including subclinical PCV2 infections, HAVE BEEN MARKEDLY REDUCED" since vaccines became available in 2007.
How this level was decided
Level 1, on the rule Eric set overriding this same criterion for pseudorabies on 2026-09-03: "this disease is not a clean fit in the levels but I will override because a) I don't think outcomes would be meaningfully improved as in L3, and b) THE VACCINE IS SO GOOD THAT THERE IS LITTLE IMPERATIVE TO DEVELOP A TREATMENT." PCV2 is the same case and arguably a stronger one, because the vaccine here is not merely good but is the single intervention that turned an epidemic disease into a subclinical one across the world industry within a few years. A treatment for a pig that is already wasting would add little to a product that stops the wasting starting. NOTE THAT THIS IS NOT THE FORBIDDEN ARGUMENT: his 2026-09-02 rule bars scoring level 1 on the ground that nobody treats viral disease. The ground here is that something else already works. Unchanged.
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. ch27 27.1: "COMMERCIAL PCV2 VACCINES HAVE BEEN AVAILABLE SINCE 2007 and economic losses attributed to PCVDs, including subclinical PCV2 infections, have been markedly reduced. PCV2 is also an important coinfecting agent and VACCINATION AGAINST PCV2 CAN ASSIST IN THE CONTROL OF CLINICAL DISEASE ASSOCIATED WITH POLYMICROBIAL INFECTIONS." 27.5.1: "fully PCV2-vaccinated pigs gained 10-40 g per day more than unvaccinated pigs", and vaccination removes the need to diagnose subclinical infection at all. 27.7: sow and piglet vaccination are both beneficial; "an overall immune CROSS-PROTECTION AMONG PCV2 GENOTYPES HAS BEEN DEMONSTRATED"; and "PCV2 vaccines based on a combination of different genotypes are now commercially available". The limitations recorded are about application rather than product: "most of the reported PCV2 vaccination failures have been CORRECTLY ATTRIBUTED TO SUBOPTIMAL VACCINATION APPLICATION". shic_2026_pcv3: "There is no cross-protection between PCV3 and other PCVs, including PCV2." PCV2 control includes "vaccination".
How this level was decided
Level 1 on the first clause -- effective vaccines are widely available in the US -- and this is one of the least equivocal C8 cells in the register. The products are commercial, near-universally used, cross-protective across genotypes, available in multi-genotype formulations, and the chapter attributes a global reduction in disease to them. IT IS NOT LEVEL 2, and the reason matters because level 2 is where inconsistent protection lives: the chapter says the reported failures were correctly attributed to how the vaccine was given, not to the vaccine. Compare mycoplasma_hyopneumoniae, scored level 2 on Eric's ruling, where the chapter itself says protection is "often incomplete" and vaccination does not prevent colonisation or transmission. PCV2 has no equivalent sentence. Level 1 held: PCV2 vaccination is established and effective, which is the first of the two situations level 1 holds.
Levels and evidence are generated from data/assignments/porcine_circovirus_2.yml; the overview is authored in data/overviews/porcine_circovirus_2.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.