Porcine Bunyaviruses
LEVELS: Highly unlikely; Mild; Extraordinary biosecurity required; Reference or research laboratory required; Negligible; Negligible; Little; Available, or not needed
| Register id | porcine_bunyaviruses |
| Type | virus |
| Scientific name | Porcine Bunyaviruses |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
This entry groups eight bunyaviruses that have some recorded relationship with pigs — among them Akabane, Schmallenberg, Oya, Lumbo, Tahyna and Rift Valley fever virus — as a single unit, because individually the evidence for each in pigs is too thin to assess and collectively they present one question. All are spread by insects, chiefly biting midges and mosquitoes, and their importance lies overwhelmingly in other species: Akabane and Schmallenberg cause abortion and deformed calves and lambs in ruminants, Rift Valley fever is a major disease of ruminants and people in Africa. In pigs, Akabane infection is inapparent in adults, and pigs are exposed without evident consequence — 38% of Czech wild boar were seropositive for Tahyna virus. The reference chapter's summary is the fairest statement of the position: the role of pigs in the complex ecology of the bunyaviruses is largely undefined but likely to be minor. Humans are not susceptible to Akabane or Oya; Tahyna and Lumbo circulate widely in some human populations with occasional clinical consequences; and although people are certainly susceptible to Rift Valley fever, what is known about infection in pigs does not suggest they present a significant zoonotic risk. There is no swine vaccine for any of them.
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 2026-08-31 level 2. Humans are not susceptible to Akabane or Oya, the two pigs most clearly carry; Tahyna and Lumbo do infect people but by mosquito bite, so the person acquires them from the vector.
Basis. ch41 41.3.1: "Humans are not susceptible to Akabane or Oya viruses." "Tahyna virus and the closely related Lumbo virus are widespread in some human populations, occasionally with clinical consequences." "Although humans are susceptible to RVFV, current knowledge regarding pig infection does not indicate a significant zoonotic risk associated with this virus." "Overall, the role of pigs in the complex ecology of bunyaviruses is largely undefined but likely to be minor."
How this level was decided
MOVED L2 -> L1, re-read 2026-09-04 AGAINST THE REWORDED LABELS. ch41 41.3.1: humans are not susceptible to Akabane or Oya, the two pigs most clearly carry. Tahyna and Lumbo do infect people, but by mosquito bite, so the person acquires them from the vector rather than from a pig. "the role of pigs... likely to be minor."
PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: INFERRED, and the entry pulls apart because it is a group. The two bunyaviruses pigs most clearly carry -- Akabane and Oya -- do not infect humans at all. Tahyna and Lumbo do, and pigs and wild boar are seropositive for them, but both are mosquito-borne and a person acquires them from the mosquito rather than from a pig. The chapter's own summary is that the role of pigs is likely minor. That leaves a pig-sourced route that is plausible, has never been reported, and has no control point directed at it -- both clauses of level 2. Level 1 is defensible if the mosquito cycle is read as making the pig a co-victim, which is the dead-end pattern Eric ruled on for chikungunya.
C2 Zoonotic impact
Severity of human illness caused by the agent
Mild: Human illness is usually mild and self-limiting, and serious disease occurs only rarely
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c2l2, disease could be expected to produce some clinical signs but no evidence that they are life threatening or severe"
Basis. ch41 41.3.1: Tahyna and Lumbo are "widespread in some human populations, occasionally with clinical consequences". Humans are not susceptible to Akabane or Oya. The chapter describes no human clinical course for any of them.
How this level was decided
INFERRED. "Occasionally with clinical consequences" in populations where infection is widespread describes an illness that is usually inapparent or mild -- Tahyna causes a self-limiting febrile illness. Level 2. FLAGGED: the registered members include Rift Valley fever virus, whose human disease is severe and can be haemorrhagic, and if the entry is scored on that member this is level 4. Scored on the typical situation the entry represents, as the general rule directs, and the chapter says pig susceptibility to RVFV "remains unresolved".
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
Basis. ch41 41.3.2: "Akabane and Oya viruses are found worldwide, except Europe, and are transmitted to vertebrates by culicoid midges and mosquitoes." "Lumbo (Africa) and Tahyna viruses (Asia, Africa, and Europe) are mosquito-borne viruses." "Akabane virus may be prevalent in pig populations in Asia, with biting midges (Culicoides spp.) serving as the primary vectors." 38% of Czech wild boars were seropositive for Tahyna virus.
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: RENUMBERED L4 -> L5 on 2026-09-01, when C3 went from four levels to five. The argument below is unchanged and so is the judgment. What changed is the scale it sits on. C3 now runs on the EFFORT REQUIRED TO EXCLUDE: L1 already in the herd, L2 housing alone keeps it out, L3 routine biosecurity keeps it out, L4 extraordinary biosecurity required, L5 exclusion may not be achievable. Arthropod vectors and a wildlife reservoir, which is the level 4 definition word for word. Culicoides midges and mosquitoes are not closed by farm biosecurity, and wild boar carry the virus. Level 4. NOTE: the chapter records that Akabane transmission in pigs "may not be completely arthropod dependent", since oronasal exposure infected pigs experimentally -- which adds a route rather than removing 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. ch41 41.3.4: "Bunyaviruses may be recovered in suckling mice or on susceptible cell culture systems, including hamster lung (HmLu-1), baby hamster kidney (BHK-21) cells, monkey kidney cells (Vero, MA-104, MARC-145), and mosquito cell lines. Techniques for bunyavirus detection and identification include TEM, serology, immunohistochemistry, reverse transcriptase-PCR, and sequencing." 41.3.3: "Akabane virus infection is inapparent in adult swine."
How this level was decided
Nothing in the pig prompts a test, since infection is inapparent. The methods listed are research and reference work -- suckling mouse inoculation, mosquito cell lines, TEM and sequencing are not a diagnostic service, and no assay is described as available for swine. Level 3.
C5 Production cost
Financial impact on the infected farm's cost of production
Negligible: No measurable effect on cost of production
Basis. ch41 41.3.3: "Akabane virus infection is inapparent in adult swine." "Under experimental conditions, Akabane virus (isolate NT-14) did not produce gross lesions, but mild lymphocytic encephalitis and cerebral vasculitis were observed." "Clinical signs and lesions have not been described for Tahyna, Lumbo, and other bunyaviruses." "Little research on the pathogenesis of bunyaviruses in pigs has been reported."
How this level was decided
Inapparent in adults, no gross lesions experimentally, and no clinical signs described at all for the other members. Level 1. NOTE: the chapter does not know whether Akabane causes lesions in pregnant sows or their fetuses, which is where the cost would be if there is one -- a real gap rather than a demonstrated absence.
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, I don't think we have any reason to think there would be market impact based on a pig diagnosis, though there would be some regulatory investigation I suspect"
Basis. Section 41.3 records no trade measure, movement control or consumer response for any porcine bunyavirus. Akabane seropositivity reaches 99% in Taiwanese sow herds without regulatory consequence.
How this level was decided
INFERRED. Seroprevalence approaching 99% in some national pig populations with no market effect anywhere in the record. Level 1.
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. ch41 41.3.5: "There are no effective treatments or vaccines available for bunyavirus infection in pigs." 41.3.3: infection is inapparent in adult swine and no clinical signs are described for the other members.
How this level was decided
No treatment exists, but the second clause of level 1 carries it: there is no clinical disease in pigs to recover from. Level 1.
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. ch41 41.3.5: "There are no effective treatments or vaccines available for bunyavirus infection in pigs."
How this level was decided
INFERRED reading of a supported fact: no vaccine exists, and under the reworded criterion the question is whether one is warranted. With infection inapparent in adults and no clinical signs described for the other members, there is no unmet need in pigs to record. Level 1 on the second clause.
Levels and evidence are generated from data/assignments/porcine_bunyaviruses.yml; the overview is authored in data/overviews/porcine_bunyaviruses.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.