Bovine Viral Diarrhea Virus in Swine
LEVELS: Highly unlikely; No human illness; Housing alone keeps it out; Laboratory-dependent; Negligible; Negligible; Little; Available, or not needed
| Register id | bovine_viral_diarrhea_virus |
| Type | virus |
| Scientific name | Bovine viral diarrhea virus 1 |
| NCBI taxid | 11099 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Bovine viral diarrhea virus is a pestivirus of cattle that occasionally infects pigs, and it is on this register mainly for two reasons that have nothing to do with sick pigs. In the field, infection of pigs usually happens without any clinical signs; the virus is relatively harmless to pigs after birth, causing at most a slight rise in temperature and minor blood changes. It can infect the fetus, though experimental attempts to reproduce transplacental infection with several strains failed entirely. The first reason it matters is diagnostic: BVDV cross-reacts with classical swine fever virus, so in CSF-free countries every suspect case has to be tested for it, and a positive pestivirus result that is really BVDV can otherwise look alarming. The second is how pigs get it — from cattle. Contaminated whey or milk fed to sows, contact with recently vaccinated cattle, and staff and equipment moving between the cattle and pig units on a mixed farm are the recognised routes, and historically contaminated live vaccines were another. Antibody prevalence in pigs in CSF-free countries runs from about 1.6% to 43.5%. There is no treatment, and the chapter records little interest in vaccinating pigs against it. 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."
How this level was decided
Level 1, stated outright for the whole genus.
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. No human infection with pestiviruses is on record.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Housing alone keeps it out: Raising pigs indoors and off soil breaks the cycle, so no ongoing biosecurity program is needed and only outdoor herds stay exposed
Corrected by Eric from L3 Routine biosecurity keeps it out. Reason: MOVED L3 -> L2. His words: "l2, this is somewhere between l2 and l3 but I think major route of transmission would be contact with live ruminant or their feces - the feed exposure should be controlled already because unpasteurized milk should not be in commercial feed or even homemade feed for that matter. WE DID NOT AGREE THAT SPECIES SEPARATION IS PART OF L3 ROUTINE BIOSECURITY. SPECIES SEPARATION IS DONE BY MOVING PIGS INSIDE." THAT LAST SENTENCE IS A RULE ABOUT THE CRITERION, not about this entry: species separation belongs to level 2, not level 3. It governs border disease virus, malignant catarrhal fever and influenza D as well, and any future agent whose reservoir is another farmed species. The level 3 list -- quarantine, transport and fomite control, C&D, monitoring -- is about what comes in through the pig supply chain.
Basis. ch35 35.4.3: "Cattle are the most common source of BVDV infection in pigs. Potential sources of infection in pigs include BVDV-contaminated whey or milk fed to sows, contact with cattle recently vaccinated with BVDV, and in cases where pigs and cattle were kept in separate lots and buildings, movement of personnel and equipment between the different farm units." "Pigs may also become infected through the use of modified live virus vaccines (CSF or Aujeszky's disease) or other biologicals contaminated with virus." 35.4.9: "To prevent BVDV or BDV infection in pigs, it is necessary to avoid direct or indirect contact with cattle or sheep. Natural infection with BVDV often occurs when pigs are fed with cow's milk or bovine offal and these practices should be avoided." 35.4.1: "interspecies transmission may occur in countries where pigs are raised in close contact with ruminants."
How this level was decided
Level 3, and the chapter writes the level 3 programme out as a list. Every route it names -- ruminant contact, bovine milk or whey in the ration, personnel and equipment moving between species units, and contaminated biologicals -- is closed by a routine biosecurity programme: species separation, feed sourcing, movement control between units, and supplier testing of vaccine cell lines and serum. It is not level 2, because housing alone does not stop a contaminated feed ingredient or a contaminated vaccine. It is not level 5, because although the reservoir is genuinely outside the pig industry, a specialised US pig unit has no ruminant contact by construction and the route is a management choice rather than an ambient pressure. NOTE ON WHAT THIS ENTRY IS: the register unit is this ruminant pestivirus IN SWINE, so every cell is scored on what it does to pigs and how it gets into a pig herd, not on what it costs the cattle or sheep industry.
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 35.4.5: "In the field, infection of pigs with BVDV usually occurs without clinical signs." 35.4.7: "rRT-PCR is the preferred method to detect either BVDV or BDV RNA. rRT-PCR is not only rapid but has higher sensitivity than virus isolation or antigen detection methods. While broadly or pan-pestivirus reactive assays can be initially used to screen samples, higher diagnostic sensitivity can be achieved using virus-species specific rRT-PCR assays." "In CSFV-free countries, BVDV and BDV must be considered in the differential diagnosis of CSFV and all CSFV suspect cases should be tested for BVDV and BDV."
How this level was decided
Level 2. Nothing points here clinically -- field infection of pigs is usually silent, and where it is not the picture resembles congenital classical swine fever -- so level 1 is out. But BVDV is endemic in US cattle and every veterinary diagnostic laboratory in the country runs validated BVDV rRT-PCR daily for the cattle industry, so the assay is available locally and regionally the moment it is asked for. The chapter makes it routine for a different reason too: US laboratories must test CSFV suspects for BVDV and BDV to rule them out. NOTE the interpretive trap: pestivirus antibodies in pig sera cross-react in CSFV serology and "often cause false positive reactions".
C5 Production cost
Financial impact on the infected farm's cost of production
Negligible: No measurable effect on 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. "c5l1, agree with assessment"
Basis. ch35 35.4.5: "In the field, infection of pigs with BVDV usually occurs without clinical signs." 35.4.4: "BVDV and BDV are pathogenic for fetal pigs, but relatively nonpathogenic for pigs after birth, apart from a slight increase in body temperature and a slight leukopenia and/or thrombocytopenia in some pigs." "BDV seems to be more consistently pathogenic for fetuses, whereas variable results are obtained with BVDV viral strains." Three separate experimental studies inoculating pregnant gilts with BVDV2 strains SV-253 and SV-260 found no transplacental infection at all. 35.1: infection with BVDV "can result in disease, especially reproductive loss, but with limited clinical impact." Ferrara 2024 measured 2.9% animal-level and 18.75% herd-level seroprevalence in 414 southern Italian pigs, comparable to the Netherlands (2.5% in sows) and Brazil (5.35%), with no disease association reported.
How this level was decided
Level 1. Field infection is usually silent, post-natal infection is close to harmless, and the reproductive damage that would make this expensive is exactly what the recent experimental work fails to reproduce -- three studies inoculating pregnant gilts with BVDV2 found no transplacental infection. Ferrara adds the field measurement the chapter lacks: about 3% of pigs in a mixed-farming region of Italy have met the virus and nobody noticed. Under the standing note SCORING/production_cost_impact, scored on modern US production where pigs and cattle are not co-located, there is no measurable effect on cost of production. FLAGGED as a level 1 or 2 judgment: the chapter does record breeding problems and a few abortions from natural infection, and this entry is deliberately scored a level below border_disease_virus on the chapter's own statement that BDV is the more consistently fetopathogenic of the two.
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. BVDV in pigs has been recognised since the 1960s, reported from Austria, Brazil, China, Denmark, Germany, Ireland, the Netherlands and Norway among others (ch35 35.4.3), and measured at 1.6-43.5% antibody prevalence in the pig populations of CSFV-free countries. Ferrara 2024 found 18.75% herd prevalence in southern Italy. No trade measure, movement control or consumer response is recorded anywhere in section 35.4.
How this level was decided
Level 1. There is abundant observed precedent, which is what SCORING/market_impact requires: sixty years of detection across a dozen countries, herd prevalence approaching a fifth in some surveys, and no market move on record anywhere. NOTE the one real consequence the chapter does record, which is regulatory rather than commercial: pestivirus antibodies in pig sera cause false positives in CSFV serosurveys and complicate CSFV eradication campaigns. That is a cost to a control programme, not a disruption to pork supply or demand.
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. Chapter 35 describes no treatment for BVDV in pigs. 35.4.5: "In the field, infection of pigs with BVDV usually occurs without clinical signs." 35.4.4: "relatively nonpathogenic for pigs after birth".
How this level was decided
Level 1 on the second clause. Animals recover acceptably without treatment because most of them are never ill, and where harm occurs it is transplacental and already done. Under the standing note SCORING/treatment_potential there is no imperative to treat.
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 35.4.8, in the chapter's own words: "There is little interest in establishing protection by vaccination in pigs against BVDV or BDV. Consequently, there has been little done to study the immune response of pigs to these viruses."
How this level was decided
Level 1 on the second clause, and the chapter states the clause rather than implying it. BVDV vaccines are ubiquitous in the cattle industry, so the technology plainly exists -- what does not exist is any reason to use one in pigs. That is exactly what "the disease does not clinically or economically justify vaccinating" was widened to hold. NOTE the chapter's warning that cuts the other way: cattle vaccinated with modified live BVDV are themselves a source of infection for in-contact pigs.
Levels and evidence are generated from data/assignments/bovine_viral_diarrhea_virus.yml; the overview is authored in data/overviews/bovine_viral_diarrhea_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.