TTSVs/Anelloviruses
LEVELS: Highly unlikely; No human illness; Already in the herd; Reference or research laboratory required; Negligible; Negligible; Little; Available, or not needed
| Register id | torque_teno_sus_viruses |
| Type | virus |
| Scientific name | Torque teno sus virus |
| NCBI taxid | 869560 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Torque teno sus viruses, also called swine anelloviruses, are small DNA viruses that pigs carry universally and that may not cause disease at all. They are ubiquitous worldwide and have been in the pig population for a long time — a retrospective study found them in Spanish pigs as early as 1985. They turn up in tissue, blood, semen, colostrum, nasal secretions and faeces, so they pass both between animals and from sow to piglet. The honest summary is the reference chapter's own: they are found in a high proportion of apparently healthy animals, no clinical signs are specifically associated with infection, and the association with disease is unsettled. Associations have been reported with PCV2 systemic disease, a dermatitis-and-nephropathy-like syndrome, reduced weight gain and respiratory disease, but there are contrary reports for the first of these, and the consequences for herd health have not been established. Working on them is difficult: no reliable cell culture system exists, no isolation protocol has been described, and there are no commercial diagnostic kits — everything is research PCR. There is no documented transmission to people, and they appear to be specific to domestic and feral swine.
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. ch41 41.2.1: "There is no documented transmission of swine anelloviruses to humans." "TTSV DNA has been found in human drugs containing components of swine origin, but the medical significance is undetermined." 41.2.2: "TTSVs are considered host species-specific, and there is no evidence of infection in species other than domestic and feral swine."
How this level was decided
Level 1. The chapter is careful to distinguish viral DNA turning up in human samples from infection: TTSV genome has been found in pork and in human faeces, and it says the latter "probably represents ingested pork products containing viral DNA". Detecting a genome in a stool is not transmission.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. ch41 41.2.1: "There is no documented transmission of swine anelloviruses to humans." Human TTVs exist but are separate viruses, and even for those "a causal role for TTV has not been established in any species".
How this level was decided
C2 scores level 1 whenever the agent does not cause disease in people. No human illness is attributed to a swine anellovirus.
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. ch41 41.2.2: "TTSVs appear to be ubiquitous worldwide." "A retrospective study showed that TTSVs were present as early as 1985 in Spain, suggesting its spread in the pig population for a long period of time." "TTSVs can be detected in tissues, blood, semen, colostrum, nasal, and fecal samples, indicating the potential for both horizontal and vertical transmission."
How this level was decided
Ubiquitous worldwide for at least forty years, transmitted both horizontally and vertically including through semen and colostrum. Carried by the pigs themselves with no introduction event to prevent. Level 1.
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 41.2.4: "The described diagnostic methods have been used in research, and no commercial diagnostic kits are available." Several PCR and qPCR assays exist, plus in situ hybridisation where "in some cases the results were not definitive", and research ELISAs. 41.2.2: "no consistent in vitro cell culture system has been identified". 41.2.4: "No efficient protocols for TTSV isolation have been described." Hawko 2022, a dedicated review section on TTSuV, supports the level already scored: "Molecular testing of TTSuV can be performed on serum samples by conventional nested polymerase chain reaction (PCR) and real-time PCR as well as in the liver, spleen, heart, tonsils, and in normal blood of stillborn fetuses", with an ISH DNA probe reported by two groups. Nested PCR and an in-house ISH probe are research and reference laboratory methods rather than a diagnostic service, and the review adds the lesion literature the chapter lacks -- experimental TTSuV1 in gnotobiotic pigs giving interstitial pneumonia and membranous glomerulonephropathy, TTSuV2 giving microscopic lesions with no gross ones, and Polster 2022 reporting non-suppurative encephalitis in TTSuV1-positive animals.
How this level was decided
Level 3. The chapter states the position the reworded criterion asks about: the assays exist and are real, but they live in research laboratories and no commercial kit is available. Nothing here is a test a practitioner can request. Not level 4, because the PCR assays are established and used across multiple published studies rather than being a single unevaluated primer set.
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, like chlamydia in pigs, enormous work has been done to try to make this agent into a disease causing pathogen but aside from some evidence that it may potentiate PCV2, I don't think there is enough evidence to say it has any cost on production"
Basis. ch41 41.2.3: "TTSVs may be found in a high proportion of apparently healthy animals, which suggests that infection by itself does not produce clinical signs." "At present, no clinical signs are specifically associated with TTSV infection." "The association of TTSV with disease is unsettled." 41.2.5: "The impact of TTSV infection and the consequences for herd health have not been established." Associations are recorded with PCV2-SD, a PDNS-like condition, reduced weight gain and respiratory disease, but for PCV2-SD "there are also contrary reports".
How this level was decided
INFERRED, and scored rather than left unassessed because the chapter positively examines causation rather than being silent on it. It concludes that infection by itself does not produce clinical signs, that no clinical signs are specifically associated with it, and that the disease associations are unsettled with contrary reports. That is an examined negative, which is evidence -- the distinction drawn on the ch36 batch between porcine_kobuvirus, scored level 1, and pasivirus_a, left unassessed. Level 1. NOTE: the chapter also says the impact has not been established, which is a fair basis for Eric to prefer no level.
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, the agent is widespread and has been identified for decades, there is no effect on markets"
Basis. Section 41.2 records no trade measure, movement control or consumer response. TTSVs have been ubiquitous in pigs worldwide since at least 1985.
How this level was decided
INFERRED. An agent present in essentially every pig for four decades, with no attributed clinical syndrome and no regulatory status, has no mechanism to move pork supply or demand. 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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c7l1, there is no economic or clinical imperative to create a treatment"
Basis. No antiviral is described in ch41 41.2. 41.2.3: "no clinical signs are specifically associated with TTSV infection".
How this level was decided
INFERRED. C7 asks how much better outcomes would be with a treatment, and no clinical outcome is attributed to this agent. Second clause of 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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c8l1, there is no economic or clinical imperative to create a vaccine"
Basis. ch41 41.2.5 reports one study in which "TTSV viremia was controlled by a combined DNA and protein immunization", and that PCV2 vaccination "did not alter TTSV loads". No vaccine is available. "The impact of TTSV infection and the consequences for herd health have not been established."
How this level was decided
INFERRED. An experimental immunisation has controlled viraemia, so the target is not intractable -- but no product exists and the chapter says the herd-health impact has not been established, so there is no demonstrated need for one. Level 1 on the second clause. NOTE: if TTSV is confirmed as a cofactor in PCV2-SD, which the chapter leaves undetermined, this becomes level 3.
Levels and evidence are generated from data/assignments/torque_teno_sus_viruses.yml; the overview is authored in data/overviews/torque_teno_sus_viruses.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.