European PRRSV-1

LEVELS: Highly unlikely; No human illness; Extraordinary biosecurity required; Laboratory-dependent; Moderate; Negligible; Substantial; Needed but not available


Register id	`prrsv_1`
Type	virus
Scientific name	Betaarterivirus europensis
NCBI taxid	3411021
Evidence	1 document(s)
Assigned	2026-09-04, against criteria version `093366e352a2`

Overview

PRRSV-1 is the European genotype of porcine reproductive and respiratory syndrome virus. Although it and the North American PRRSV-2 cause the same clinical picture — reproductive failure in the breeding herd, pneumonia and poor growth in young pigs, and a general worsening of every other respiratory infection present — they are distinct enough genetically and antigenically that a vaccine or an immune response against one gives limited protection against the other. PRRSV-1 predominates in Europe and is present in parts of Asia, and it is not established in the United States, where it has been detected only rarely. Like its counterpart it spreads in pigs, semen, on vehicles and equipment and by air, evolves continually, and cannot be excluded from a breeding herd by routine biosecurity alone. Highly virulent PRRSV-1 subtypes circulating in eastern Europe cause disease as severe as anything seen with PRRSV-2. The register scores the two genotypes separately because reviewers expect the split, not because the scores are expected to differ much.

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

How this level was decided

Level 1, identical to prrsv_2 and for the same sentence. The chapter forecloses the question at the cell-culture level, so this is not exposure without disease but no susceptibility at all.

C2 Zoonotic impact

Severity of human illness caused by the agent

No human illness: Agent does not cause illness in people

How this level was decided

Level 1, following C1 and identical to prrsv_2.

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. THE TWO PRRSV ENTRIES ARE SCORED AGAINST EACH OTHER DELIBERATELY. The register keeps them apart on your 2026-08-18 ruling -- "reviewers expect the two genotypes assessed separately; SCORES ARE EXPECTED TO BE SIMILAR BUT FACE VALIDITY REQUIRES THE SPLIT" -- and ch37 treats them jointly for the same reason it can: 37.1, "PRRSV refers to both species, unless otherwise noted, BECAUSE PRRSV-1 AND PRRSV-2 ACT SIMILARLY IN THE HOST." Where this cell differs from prrsv_2, or deliberately does not, it is said. 37.2.1 on where each sits: "Today, BOTH SPECIES SHARE WORLDWIDE DISTRIBUTION, WITH PRRSV-1 BEING PREDOMINANT IN EUROPE AND PRRSV-2 PREDOMINANT IN THE AMERICAS AND ASIA." The two "vary by about 44% in nucleotide sequences". The exclusion measures in ch37 37.10.1 are described for PRRSV without distinction: "for breeding herds in some swine-dense regions, prevention MAY INCLUDE THE USE OF AIR FILTRATION or air treatment systems, such as UV light... air filtration led to about 80% REDUCTION IN RISK of novel PRRSV introduction", and "BIOSECURITY CONTROL MEASURES ABLE TO ADDRESS ALL HAZARDS ARE GENERALLY LACKING." 37.4.5.3: "identifying the exact route by which a herd became infected CAN BE CHALLENGING IN PRACTICE." Environmental behaviour is described for PRRSV as a whole -- quickly inactivated by heat and drying, up to 11 days in water, inactivated by common disinfectants.

How this level was decided

Level 4, the same as prrsv_2, and the sameness is the point rather than a shortcut. C3 asks what effort excludes the agent, and the answer is a property of how the virus moves rather than of which species it is: the transmission biology, environmental stability and disinfectant susceptibility in this chapter are all written for PRRSV without separating the two, and air filtration filters both. NOTE THE ONE ASYMMETRY AND WHY IT DOES NOT LOWER THE LEVEL: PRRSV-1 is predominant in Europe rather than the Americas, so a US herd meets it far less often. That is a difference in how often the introduction is attempted, not in what it takes to prevent one, and C3 measures the second.

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

How this level was decided

Level 2, the same as prrsv_2. The commercial assays are explicitly designed to detect and DIFFERENTIATE the two species, so a US laboratory finding PRRSV-1 rather than PRRSV-2 is a routine result rather than a special exercise -- which is the fact that keeps this cell level with its sibling instead of at level 3. The presentation points no better here than it does for PRRSV-2.

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, exactly according to desc in criteria"

Basis. THE TWO PRRSV ENTRIES ARE SCORED AGAINST EACH OTHER DELIBERATELY. The register keeps them apart on your 2026-08-18 ruling -- "reviewers expect the two genotypes assessed separately; SCORES ARE EXPECTED TO BE SIMILAR BUT FACE VALIDITY REQUIRES THE SPLIT" -- and ch37 treats them jointly for the same reason it can: 37.1, "PRRSV refers to both species, unless otherwise noted, BECAUSE PRRSV-1 AND PRRSV-2 ACT SIMILARLY IN THE HOST." Where this cell differs from prrsv_2, or deliberately does not, it is said. 37.2.1 on where each sits: "Today, BOTH SPECIES SHARE WORLDWIDE DISTRIBUTION, WITH PRRSV-1 BEING PREDOMINANT IN EUROPE AND PRRSV-2 PREDOMINANT IN THE AMERICAS AND ASIA." The two "vary by about 44% in nucleotide sequences". ch37 37.1: "PRRSV-1 and PRRSV-2 act similarly in the host", and PRRS "remains one of the most globally significant swine diseases due to its wide distribution, POTENTIALLY CATASTROPHIC ECONOMIC IMPACT, and the lack of consistently effective control measures." On severe variants of this species specifically, 37.5: "SEVERAL ATYPICAL PRRSV-1 ISOLATES HAVE ALSO EMERGED IN EUROPE SINCE 2009." The US per-pig loss figures in 37.10.1 -- $2.29 rising to $5.70 per pig placed -- are given for PRRSV without distinguishing the species, in a country where PRRSV-2 predominates.

How this level was decided

INFERRED. Level 3, the same as prrsv_2, and inferred rather than supported because the quantified US losses cannot be attributed to this species. THE REASON IT DOES NOT DROP BELOW ITS SIBLING is that C5 asks what the agent costs THE INFECTED FARM, not what it costs the national herd. On a US farm that has PRRSV-1, the disease behaves as the chapter says it behaves -- similarly in the host -- and Europe has had severe atypical isolates of this species since 2009. A lower level here would be scoring prevalence, which belongs to C3, into a criterion that asks about magnitude on the affected unit.

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, industry is accustomed to the agent and if incursion, would not anticpate any market effect"

How this level was decided

INFERRED. Level 1 under the standing note SCORING/market_impact, the same as prrsv_2. PRRSV is diagnosed in US pigs at enormous scale and the market has never responded; nothing suggests a report naming the European species rather than the American one would behave differently.

C7 Treatment potential

Potential for treatment to improve outcomes

Substantial: No effective treatment (antimicrobial, antiviral, antiparasitic, herbal or other) is available, but outcomes would meaningfully improve if one existed

How this level was decided

Level 3, the same as prrsv_2. No effective treatment exists and outcomes would meaningfully improve if one did -- persistent infection, endemic circulation in nursery and finisher pigs, and reproductive loss in breeding herds are all things a treatment would act on. The standing note SCORING/treatment_potential governs: C7 scores the value of a treatment that does not exist, not the industry's willingness to use one.

C8 Vaccine availability

Availability of effective vaccines or bacterins

Needed but not available: No effective vaccine is available in the US or has been developed, and the disease would justify vaccinating if one existed

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

Confirmed by Eric. CONFIRMED. "c8l3, vaccines exist but not in US, they are licensed commercial products, shold be easy to access if need became acute in US"

Basis. THE TWO PRRSV ENTRIES ARE SCORED AGAINST EACH OTHER DELIBERATELY. The register keeps them apart on your 2026-08-18 ruling -- "reviewers expect the two genotypes assessed separately; SCORES ARE EXPECTED TO BE SIMILAR BUT FACE VALIDITY REQUIRES THE SPLIT" -- and ch37 treats them jointly for the same reason it can: 37.1, "PRRSV refers to both species, unless otherwise noted, BECAUSE PRRSV-1 AND PRRSV-2 ACT SIMILARLY IN THE HOST." Where this cell differs from prrsv_2, or deliberately does not, it is said. ch37 37.10.6, AND THIS IS THE ONE SENTENCE IN THE CHAPTER THAT SEPARATES THE TWO SPECIES ON A CRITERION: "COMMERCIAL PRRSV-1 MLV VACCINES ARE AVAILABLE FOR USE IN EUROPE AND ASIA, AND COMMERCIAL PRRSV-2 MLV VACCINES ARE AVAILABLE GLOBALLY (WITH SOME EXCEPTIONS)." On whether a PRRSV-2 product would cover this species, the chapter is discouraging: the two "vary by about 44% in nucleotide sequences" (37.2.1), and field vaccine failure is attributed in part to "INADEQUATE CROSS-PROTECTION" even between variants of the SAME species. On whether the disease warrants a vaccine: PRRS is "one of the most globally significant swine diseases" with "potentially catastrophic economic impact" (37.1), and Europe -- where this species predominates -- vaccinates against it commercially.

How this level was decided

Level 3, AND THIS IS THE ONLY CELL WHERE THE PRRSV SPLIT EARNS ITS KEEP. FLAGGED, because it makes the two entries differ and because it turns on US licensure, which is exactly the kind of fact you have told me to ask about rather than assume. THE READING: C8 asks about availability IN THE US -- level 1 says "widely available in the US or secured for national outbreak response" -- and the chapter places PRRSV-1 MLV vaccines in Europe and Asia while placing PRRSV-2 products globally. If no PRRSV-1 vaccine is licensed in the US, then a US herd that gets PRRSV-1 has no matched product, and cross-protection from a PRRSV-2 vaccine is poor across a 44% nucleotide difference when it is already inadequate within a species. That is level 3 -- needed but not available -- and the disease plainly warrants vaccinating, since Europe does. WHAT WOULD MOVE IT TO LEVEL 2: any US-licensed PRRSV vaccine carrying a PRRSV-1 claim, or your judgment that US PRRSV-2 products give usable cross-protection in practice. YOU WILL KNOW THIS AND I DO NOT. If you move it to 2, the two entries become identical on all eight criteria, which is a defensible outcome and would be worth recording as such -- the split would then rest on face validity alone, which is the reason you gave for making it.

Levels and evidence are generated from data/assignments/prrsv_1.yml; the overview is authored in data/overviews/prrsv_1.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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