Porcine Bocaviruses

LEVELS: Highly unlikely; No human illness; Already in the herd; No validated assay; Minor; Negligible; Little; Available, or not needed


Register id	`porcine_bocaviruses`
Type	virus
Scientific name	Porcine bocavirus
NCBI taxid	1165907
Evidence	6 document(s)
Assigned	2026-09-06, against criteria version `093366e352a2`

Overview

The porcine bocaviruses are a group of four parvoviruses first found in Swedish pigs in 2009 and since detected across Asia, Europe, Africa and North America. For most of the intervening years almost nothing could be said about them, because nobody could grow them in cell culture and so nobody could test whether they cause disease. That changed very recently: the first successful isolations and the first experimental pathogenicity studies in fifteen years were published in 2025 and 2026, and they showed an age-dependent effect, with young piglets developing clinical signs lasting three or four days and shedding virus for up to two weeks, with no deaths in any age group. A serological test — an ELISA against a synthetic capsid peptide — was likewise only developed in 2024, because effective antibody assays did not exist before. The picture that emerges is of a common, mild infection whose importance is still being worked out. One point of interest is that the porcine bocaviruses cluster genetically with the human bocaviruses, which are established causes of respiratory and gut illness in children, though no human infection with a pig bocavirus has been described. There is no treatment and no vaccine.

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

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED. REVIEWED ON C1_C2_RECLASSIFICATION.md, 2026-09-04, after the C1/C2 rewording that separated exposure from consequence. Eric marked up every moved cell and reversed his own earlier setting on twenty of the twenty-one: "In almost every case, I agreed with new opinion and reversed my old setting." HIS MARKUP HERE WAS "l1". Reverses his 2026-09-03 level 2. No human infection with a porcine bocavirus is reported in any of the five papers, including two 2025-2026 studies that are the first isolations in fifteen years. The basis was phylogenetic proximity alone.

How this level was decided

MOVED L2 -> L1, re-read 2026-09-04 AGAINST THE REWORDED LABELS. NO HUMAN INFECTION WITH A PORCINE BOCAVIRUS IS REPORTED IN ANY OF THE FIVE PAPERS, including two 2025-2026 studies that are the first isolations in fifteen years. The whole basis was phylogenetic proximity to the human bocaviruses.

PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: INFERRED. Level 2 -- plausible but never reported, with no control point implemented, which is the label. What the folder offers is phylogenetic proximity to the human bocaviruses and a review that raises public health as a question it intends to explore; what it does not offer is a single human case, a seroprevalence study in people, or any attributed transmission. THE ARGUMENT FOR LEVEL 1 IS STRONG AND IS THE READING YOU HAVE TAKEN REPEATEDLY THIS EVENING -- on Staphylococcus hyicus, "though isolated from humans rarely IT IS MISLEADING TO CONSIDER IT A CONSEQUENTIAL ZOONOSIS", and here the organism has not even been isolated from a human. Level 2 is scored only because a peer-reviewed review names public health as an open question rather than a closed one. If you read that as the literature overrating the potential, this is level 1 and C2 goes with it. Level 1 confirmed -- no human case has ever been reported. The cross-reactivity and recombination note is a hypothesis about future potential, and the general rule forbids scoring hypothetical variants.

C2 Zoonotic impact

Severity of human illness caused by the agent

No human illness: Agent does not cause illness in people

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED. "c2l1, no evidence of disease caused by this pig virus"

How this level was decided

INFERRED. Level 1, on your porcine rotavirus reasoning of this evening -- a plausible zoonosis on paper, but "until some evidence comes to light, I ASSUME THEY ARE MORE LIKELY TO BE INCIDENTAL INFECTIONS RATHER THAN CAUSING DISEASE". Here there is not even an incidental infection on record. IT MOVES WITH C1: if that goes to level 1 this stays where it is, and the pair then reads as a straightforward non-zoonosis. 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

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED. "c3l1, unlikely to be able to exclude thios from healthy pigs"

Basis. THE ENTRY IS A GROUP OF FOUR -- PBoV1, PBoVsx, PBoVh18 and PBoV3 -- and HAS NO DISEASES OF SWINE CHAPTER. The folder is five journal papers, four of them from 2024 to 2026, and TWO OF THEM CHANGE WHAT IS KNOWN ABOUT THIS AGENT: ji_2025 and hu_2026 are the first successful cell culture isolations and the first experimental pathogenicity studies in fifteen years. On distribution, hu_2026: "Since its initial discovery in Swedish pigs in 2009, porcine bocavirus (PBoV) HAS BEEN DETECTED ACROSS ASIA, EUROPE, AFRICA, AND NORTH AMERICA." On prevalence, gong_2024 tested 1373 sera from 12 Chinese provinces: "THE RESULTS SHOWED THAT 47.56% OF THE SAMPLES WERE PBoV G3 POSITIVE." In wildlife, prpic_2026 found PBoV DNA in 7 of 184 Croatian wild boar (3.80%), across several counties, with "no significant associations... between virus detection and age, sex, or geographic origin", concluding "LOW-LEVEL VIRAL CIRCULATION ACROSS MULTIPLE REGIONS". None of the five papers describes a route into a herd or any measure that would exclude the virus. shic_pbov: "PBoVs have been identified in North America, Asia, the UK, Eastern Europe, and Africa." "U.S. studies have documented prevalence rates in sick pigs of approximately 43% and 59%." "parvoviruses are often resistant to common disinfectants."

How this level was decided

INFERRED. Level 1 -- already in the herd. Nearly half the pigs in a twelve-province survey carry antibody, the virus is on four continents including North America, and it circulates in wild boar as well; there is no introduction event to prevent. NOTE THE GAP AND WHY IT DOES NOT CHANGE THE ANSWER, since it would matter for any other level: not one of the five papers describes how the virus moves between herds or what would keep it out. That would leave the cell empty if the question were how to protect a clean herd, and there is no clean herd described anywhere. Level 1 confirmed and now firmly supported: prevalence of 43% and 59% in US sick pigs.

C4 Detection difficulty

Difficulty of recognizing and confirming infection

No validated assay: No pathogen-specific test of known reliability exists anywhere, and identification depends on sequencing or on primers that have not been critically evaluated

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED. "c4l4, no widely available or validated reagents for detection, largely only in the research sphere"

Basis. THE ENTRY IS A GROUP OF FOUR -- PBoV1, PBoVsx, PBoVh18 and PBoV3 -- and HAS NO DISEASES OF SWINE CHAPTER. The folder is five journal papers, four of them from 2024 to 2026, and TWO OF THEM CHANGE WHAT IS KNOWN ABOUT THIS AGENT: ji_2025 and hu_2026 are the first successful cell culture isolations and the first experimental pathogenicity studies in fifteen years. gong_2024 opens by stating the gap: "CURRENTLY, EFFECTIVE SEROLOGICAL METHODS FOR THE DETECTION OF ANTIBODIES AGAINST PBoV G3 ARE LIMITED", and the paper exists to build one -- a synthetic VP1 peptide indirect ELISA, newly developed, with its own cutoff, cross-reactivity panel and coefficients of variation. ji_2025 states the other half: "THE INABILITY TO PROPAGATE PORCINE BOCAVIRUS (PBoV) IN VITRO HAS SEVERELY IMPEDED RESEARCH into its fundamental biology and pathogenic potential SINCE ITS DISCOVERY 15 YEARS AGO", and reports "THE FIRST DOCUMENTED ISOLATION OF PBoV IN A CONTINUOUS CELL LINE". prpic_2026 detected the virus by real-time PCR in a research surveillance programme. No commercial assay, and no clinical presentation exists that would prompt a test. shic_pbov: "Sequence-based methods to identify PBoV include polymerase chain reaction (PCR), TaqMan-based quantitative PCR (qPCR), multiplex qPCR, loop-mediated isothermal amplification, nanoPCR, duplex nanoPCR (PBoV and pseudorabies virus), and sequence-independent single primer amplification (SISPA)." "Monoclonal antibodies have been developed for use in an antigen-detecting enzyme linked immunosorbent assay (ELISA) and an ELISA targeted anti-PBoV IgG has recently been described." "PBoV has been successfully propagated in primary pig kidney cells."

How this level was decided

INFERRED. Level 4 -- no validated pathogen-specific assay of known reliability, with identification resting on PCR and sequencing. Both halves of the label hold: nothing about a pig would make anyone ask for this test, and the assays are research instruments. THE FOLDER DOCUMENTS THE ASSAY BEING BUILT: a serological method described as limited in 2024, with the first-ever cell culture isolation in 2025. Under the C4 rewording of 2026-08-29 the axis is whether a VALIDATED assay exists, and a peptide ELISA published last year with no independent evaluation is not yet one. THE ARGUMENT FOR LEVEL 3 is that these assays plainly work in the hands that built them, which is what a research laboratory requirement looks like; rule it as you ruled other_actinobacillus_species if you read it that way. LEVEL 4 HELD BUT FLAGGED. This is a substantial change in what the folder holds: seven named nucleic acid formats, monoclonal antibodies, two ELISAs and successful propagation in cell culture. Level 4 means no reliable test exists anywhere, and that is now hard to say. I have not moved it because the 2026-08-29 rework turns on VALIDATION rather than existence, and every method here is described in a research setting with no indication any is validated or offered diagnostically -- and the same factsheet says no experimental infection studies have been done in pigs at all, so there is no challenge model against which an assay could have been validated. If Eric reads this quantity of method as reaching level 3, it is a defensible move.

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. "c5l2, no evidence that it causes anything other than minor clincial disease"

Basis. THE ENTRY IS A GROUP OF FOUR -- PBoV1, PBoVsx, PBoVh18 and PBoV3 -- and HAS NO DISEASES OF SWINE CHAPTER. The folder is five journal papers, four of them from 2024 to 2026, and TWO OF THEM CHANGE WHAT IS KNOWN ABOUT THIS AGENT: ji_2025 and hu_2026 are the first successful cell culture isolations and the first experimental pathogenicity studies in fifteen years. THIS IS THE CELL THE NEW PAPERS CHANGE. hu_2026: "the pathogenic potential of PBoV has REMAINED UNCERTAIN due to the lack of suitable cell culture systems... EXPERIMENTAL INFECTION OF 5-8, 17-19, AND 31-33 DAYS OLD PIGLETS DEMONSTRATED AGE-DEPENDENT PATHOGENICITY, WITH ALL GROUPS DEVELOPING CHARACTERISTIC CLINICAL SIGNS INCLUDING FEVER, RESPIRATORY DISTRESS, AND DIARRHEA LASTING 3-4 DAYS. Viral shedding peaked in rectal swabs at 4 days post-infection, with persistent detection through 14 dpi... Postmortem examination revealed BROAD TISSUE TROPISM in 5-8 and 17-19 days old piglets and age-dependent pathological lesions in INTESTINAL, PULMONARY, LYMPHOID AND RENAL TISSUES." ji_2025: "EXPERIMENTAL INFECTION OF PIGLETS CONFIRMED PBoV-CNH AS A PRIMARY PATHOGEN", with dual respiratory-enteric tropism. Against that, prpic_2026 on wild boar: "although BOTH VIRUSES ARE TYPICALLY SUBCLINICAL, their detection contributes to understanding pathogen diversity." shic_pbov: "The pathogenesis of PBoV and its ability to induce clinical signs is not well understood. Viral co-infections are common in PBoV-positive pigs. To date, PBoVs have been reported in pigs with PMWS, respiratory disease, diarrhea, and in asymptomatic swine." "It does not appear that any studies of experimental PBoV infection have been conducted in pigs."

How this level was decided

INFERRED, AND WORTH A LOOK BECAUSE THE EVIDENCE MOVED. This entry would have been an "agent looking for a disease" a year ago -- your phrase for the parvoviruses earlier tonight -- and two 2025-2026 papers have now isolated the virus, infected piglets with it, and reproduced fever, diarrhoea and respiratory signs with lesions in four tissues. ONE OF THEM CALLS IT A PRIMARY PATHOGEN. LEVEL 2 IS SCORED: the illness lasts three to four days and the pigs recover, which is a small and short-lived loss, and nearly half of a large Chinese population carries antibody without a disease problem being reported. NOT LEVEL 1, because pathogenicity is now demonstrated rather than absent. NOT LEVEL 3, on your Menangle rule -- two experimental studies in Chinese laboratories are not the general case for US production, and nothing in the folder quantifies a field loss anywhere. Level 2 held.

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 evidence to date that the market has any concern about this agent"

How this level was decided

INFERRED. Level 1 under the standing note SCORING/market_impact: an agent already present and repeatedly reported in US pigs for fifteen years with no market move ever observed. NOTE THE ONE PHRASE THAT COULD BE MISREAD: a review naming trade restrictions among an agent's potential economic impacts is a list of things that could be looked into, not a record of anything happening. The note is explicit that the absence of a historical move is the evidence where the agent is already here. 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

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED AT LEVEL 1, AND THE READING IS RECORDED BECAUSE HIS MARKING CARRIED NO LEVEL DIGIT. He wrote "c7, no clinical imperative at this time that would support treatmetn developments" -- naming the criterion but omitting the number. IT IS READ AS LEVEL 1 and not guessed at: "no clinical or market imperative" is his own standing formula for the C7 and C8 level 1 "not needed" clause, used in more than thirty rulings and recorded as the operative test in the standing note SCORING/vaccine_availability; the pass had already scored level 1; and he confirmed the neighbouring cells on the same entry without changing anything. This follows the precedent set on vesicular_exanthema_of_swine_virus, where prose without a level was read rather than discarded and the reading was written into the correction so it could be checked.

How this level was decided

INFERRED. Level 1 on the second clause of the label -- animals recover acceptably without treatment -- and the ground is an examined outcome rather than a silence, which is what makes it scoreable at all. Piglets experimentally infected at three ages all developed signs and all recovered within four days. NOT SCORED LEVEL 1 BECAUSE NO ANTIVIRAL EXISTS, which your 2026-09-02 rule forbids. IT MOVES WITH C5: if the pathogenicity work turns out to describe something more serious than a four-day illness, this cell follows it. 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

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED AT LEVEL 1, AND THE READING IS RECORDED BECAUSE HIS MARKING CARRIED NO LEVEL DIGIT. He wrote "c8, no clinical imperative at this time that would support vaccine developments" -- naming the criterion but omitting the number. IT IS READ AS LEVEL 1 and not guessed at: "no clinical or market imperative" is his own standing formula for the C7 and C8 level 1 "not needed" clause, used in more than thirty rulings and recorded as the operative test in the standing note SCORING/vaccine_availability; the pass had already scored level 1; and he confirmed the neighbouring cells on the same entry without changing anything. This follows the precedent set on vesicular_exanthema_of_swine_virus, where prose without a level was read rather than discarded and the reading was written into the correction so it could be checked.

How this level was decided

INFERRED. Level 1 on the "not needed" clause, by the FIRST route in the standing note -- low clinical significance -- AND THE PCV4 RULE IS THE THING TO WATCH HERE, so it is addressed rather than avoided. That rule says asserting a vaccine is not needed is still a claim about the disease, and it cannot be made for an agent whose disease-causing potential is unknown. IT IS NO LONGER UNKNOWN: unlike PCV4, this agent has now been isolated, inoculated into piglets of three ages, and shown to cause a self-limiting three-to-four-day illness. That is enough to say a vaccine is not warranted, and it is why this cell is a level rather than a null. IF YOU READ THE TWO EXPERIMENTAL PAPERS AS TOO THIN to carry a claim about the disease, then C5, C7 and C8 should all be nulled together and the entry leaves the export. LEVEL 1 HELD, AND FLAGGED against the standing note's hard limit. The note forbids level 1 as a default where the agent's disease-causing potential is UNKNOWN -- that is why pcv4 and parechovirus_a carry nulls -- and this factsheet says in terms that little is known about PBoV including its pathogenicity, with no experimental infection ever done. On the strict reading this cell should be null. It is not obviously the same case as pcv4: PBoV has been found in 43-59% of sick US pigs and in asymptomatic ones, which is closer to a demonstrated commensal than to an uncharacterised agent. Eric set that boundary and should place this entry against it.

Levels and evidence are generated from data/assignments/porcine_bocaviruses.yml; the overview is authored in data/overviews/porcine_bocaviruses.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.

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