Campylobacter spp.
LEVELS: Sometimes occurs; Moderate; Already in the herd; Laboratory-dependent; Negligible; Negligible; Little; Available, or not needed
| Register id | campylobacter_spp |
| Type | bacteria |
| Scientific name | Campylobacter |
| NCBI taxid | 194 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
This entry covers Campylobacter coli and C. jejuni together, grouped because they present no clinical or risk difference in pigs. Pigs are a natural reservoir and carry them at very high rates — usually 50–100% of animals in commercial herds worldwide — with piglets picking the organisms up from the sow within a week of birth. Yet they are not pig pathogens: swine are asymptomatic carriers, and even experimentally infected weaned piglets show no clinical or pathological signs, so the organism's significance as a cause of disease in pigs is regarded as negligible. Its importance is entirely a food-safety one, and even there the pig's contribution is modest. Campylobacter is a major cause of human gastroenteritis and is linked to Guillain- Barré syndrome, reactive arthritis and irritable bowel syndrome, but source attribution studies consistently implicate swine as a small or negligible contributor; pork-associated cases are documented but infrequent, and standard chilling and carcass interventions at slaughter are highly effective at reducing or eliminating it. Given how ubiquitous it is on farms, on-farm control would be extremely challenging, and no serious effort has been directed at it.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Sometimes occurs: Known risk of transmission to humans (foodborne or occupational), but requires failure of one or more control points for transmission to humans
Basis. "The role of swine in human Campylobacter infections is much smaller and reported to be insignificant in many instances." "The vast majority of source attribution studies consistently implicate swine as a small or negligible contributor to human infections caused by Campylobacter." "However, it is important to underline that the association of swine (i.e. contaminated carcasses), albeit infrequently, with human foodborne illness due to Campylobacter is clearly indicated in several reports." "C. hyointestinalis from carrier pigs can be transmitted to humans via contact and result in gastroenteritis." "standard slaughter processes (e.g. chilling and use of various nonantibiotic antimicrobial compounds) are highly effective in reducing or even eliminating Campylobacter on swine carcasses." (ch58 58.4.2, 58.4.4)
How this level was decided
Pig-to-human transmission is documented in both directions the criterion cares about -- foodborne via contaminated carcasses and occupational by contact with carrier pigs -- so this is a known risk, not merely a plausible one. It is also explicitly control-point dependent: the chapter states slaughter chilling and antimicrobial interventions are highly effective, which is why swine contribute little despite 50-100% herd carriage. Known risk requiring a control point failure is level 3.
C2 Zoonotic impact
Severity of human illness caused by the agent
Moderate: Clinically important illness is common and may require medical treatment or hospitalization, but death or permanent disability is uncommon
Basis. "Most Campylobacter-related illnesses in humans are sporadic and characterized by self-limiting watery or bloody diarrhea, abdominal cramps, and possible fever; however, severe conditions may occur in immunocompromised patients, requiring antibiotic treatment." "Campylobacter infection is also associated with Guillain-Barre syndrome and other post infectious autoimmune sequelae such as reactive arthritis and irritable bowel syndrome, which may result in serious health consequences." "Campylobacter has developed resistance to both classes of antimicrobials, posing a threat to treatment efficacy." (ch58 58.4.2)
How this level was decided
The typical illness is self-limiting, which alone would read as level 2, but the chapter records two things that lift it: severe disease in immunocompromised patients requiring antibiotics, and Guillain-Barre syndrome and reactive arthritis as recognised sequelae. Clinically important illness that commonly needs medical treatment, with death or permanent disability real but uncommon, is level 3. Not level 4 -- GBS is a recognised but uncommon outcome, not a substantial share of the distribution.
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. "Swine are a frequent carrier and natural reservoir of Campylobacter in the intestine, with a prevalence rate usually between 50 and 100% in commercial herds throughout the world." "piglets can acquire the organism from their mothers via the fecal-oral route within a week after birth." "Considering the ubiquitous nature of Campylobacter in the farm environment and swine herds, prevention or control at the preharvest level would be extremely challenging." (ch58 58.4.3, 58.4.4)
How this level was decided
Present in 50-100% of commercial herds worldwide and acquired from the dam in the first week of life. There is no introduction event to prevent, which is level 1 exactly. The chapter reaches the same conclusion when it says preharvest control would be extremely challenging.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "l2, straightforward to confirm by most laboratories"
Basis. "none of the Campylobacter spp. are currently considered as an established cause of disease in pigs." "swine are considered asymptomatic carriers of Campylobacter under natural settings." "Isolation of Campylobacter from various sources (including live swine and pork) is carried out via a variety of selective culture methods, while identification and species differentiation can be performed by biochemical tests, PCR, and MALDI-TOF mass spectrometry." (ch58 58.4.1, 58.4.3)
How this level was decided
There is no clinical presentation to recognise -- carriage is asymptomatic -- so nothing would prompt a practitioner to suspect it, ruling out level 1. Once looked for, selective culture, PCR and MALDI-TOF are standard regional laboratory and food microbiology methods. Not recognised clinically but locally confirmable is level 2.
C5 Production cost
Financial impact on the infected farm's cost of production
Negligible: No measurable effect on cost of production
Basis. "it is widely accepted that Campylobacter does not cause any significant clinical or pathological condition in commercial swine, and thus its significance as a swine pathogen can be considered negligible." "Although C. coli and C. jejuni can readily colonize the intestine and even translocate to extraintestinal sites (e.g. spleen) in experimentally challenged weaned piglets with natural gut microbiota, no clinical or pathological manifestations are observed." (ch58 58.4.3)
How this level was decided
The chapter uses the word the level uses. No clinical disease in commercial swine means no mortality, no morbidity, no treatment cost and no lost performance. Level 1, negligible.
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. "agree c6l1, the market is not sensitive to these agents, they are common. Like many other zoonotic agents, if there were a major foodborne multistate outbreak tied back to pork, there may be a short term effect but this is the 95% percentile issue and abnormal."
Basis. "no major efforts have been directed toward prevention or control of this organism in the swine production chain." "standard slaughter processes... are highly effective in reducing or even eliminating Campylobacter on swine carcasses." The chapter records no trade measure, movement control or consumer response associated with swine Campylobacter. (ch58 58.4.4)
How this level was decided
INFERRED. Campylobacter is already present in half to all US herds and has been throughout the period in which pork has traded normally, so its presence is priced in and cannot itself disrupt supply or demand. No control programme exists to trigger movement restrictions. 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 would be so little treatment going on for these agents, even in individual pigs, we should keep it at level 1. I doubt any products currently have a label clearance for it which could support a L2, but practically we shouldk go with L1"
Basis. "none of the Campylobacter spp. are currently considered as an established cause of disease in pigs." "Since Campylobacter is not known to be associated with any overt clinical disease or pathology in live pigs... no major efforts have been directed toward prevention or control of this organism." (ch58 58.4.1, 58.4.4)
How this level was decided
INFERRED. C7 scores how much better outcomes could be if a treatment existed. There is no disease outcome in pigs to improve, so the second clause of level 1 is satisfied -- animals recover acceptably without treatment, there being nothing to recover from. Same shape of call as influenza D C7 and resolved the same way. NOTE: treating pigs to reduce human exposure is a food safety intervention, not a pathogen-directed treatment improving the pig outcome, so it does not lift this level.
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. "c8l3 is correct, though this places it at the high risk end of scale, that is the reality. Ground truth however is that the disease has so little impact and low prevalence that vaccination, even if available, would be unlikely to produce a positive return" Eric, 2026-08-28: "all seven to L1". Re-ruled after the C8 rewording of the same day. His 2026-08-27 words are unchanged and are quoted above in full -- what has moved is the level they map to. He wrote each of them to say that no vaccine is NEEDED here, and level 3 was then the only place a missing vaccine could go, so the reasoning and the level contradicted each other. The reworded level 1 holds exactly what he was describing: no vaccine exists, and the disease does not justify one. Recorded as a confirmation of the reworded pass rather than an override, because the pass now agrees with him.
Basis. ch58 58.4.4: "no major efforts have been directed toward prevention or control of this organism in the swine production chain", and no vaccine is named. Eric, 2026-08-27, same words as A. suis: "vaccination, even if available, would be unlikely to produce a positive return".
How this level was decided
MOVED L3 -> L1 by the rewording. This is the entry that made the case: the chapter says Campylobacter causes no clinical disease in commercial swine, C5 is level 1 negligible, and C7 is level 1 because there is nothing to treat. Scoring C8 at the maximum-concern level for an agent that harms no pig was the incoherence the rewording fixes. Now also the worked example for C8 level 1 in criteria_levels.yml.
Levels and evidence are generated from data/assignments/campylobacter_spp.yml; the overview is authored in data/overviews/campylobacter_spp.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.