Salmonella choleraesuis
LEVELS: Rarely occurs; Severe; Routine biosecurity keeps it out; Laboratory-dependent; Moderate; Negligible; Some; Available, or not needed
| Register id | salmonella_choleraesuis |
| Type | bacteria |
| Scientific name | Salmonella enterica |
| NCBI taxid | 28901 |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Salmonella enterica serovar Choleraesuis is the host-adapted salmonella of pigs, and it behaves quite differently from the food-poisoning serovars. Rather than causing diarrhoea it usually produces septicaemia affecting many organs at once, most often in weaned pigs under five months and typically between six and sixteen weeks. Morbidity is usually under 10%, but among the pigs that are affected the case fatality rate is high, particularly in the youngest, and the course of an outbreak is unpredictable. Nothing about the clinical picture identifies it — the same septicaemic presentation is produced by erysipelas, Streptococcus suis, the actinobacilli, and by classical and African swine fever — so confirmation requires culture. Colonisation of pigs with salmonellae is hard to avoid altogether, but disease is preventable through sanitation, clean feed, control of transport and equipment, and avoiding commingling of ages. The variety that causes most pig outbreaks in the United States, Kunzendorf, is not a common human pathogen here, though a different variety of the same serovar does cause human disease elsewhere.
C1 Zoonotic potential
Likelihood of transmission from pigs to humans
Rarely occurs: Human infection from pigs is plausible but has only rarely been reported, and specific control points are not commonly implemented to prevent transmission to humans
Basis. ch55 55.3 separates this serovar from the rest of the genus in one sentence: "S. CHOLERAESUIS IS NOT A COMMON HUMAN PATHOGEN IN THE UNITED STATES, BUT THE NON-KUNZENDORF VARIETY OF THIS SEROVAR IS A CAUSE OF HUMAN DISEASE IN OTHER COUNTRIES (Chiu et al. 2004)." 55.6.2 records which variety is the pig problem here: "THE H2S-PRODUCING VARIANT KUNZENDORF IS RESPONSIBLE FOR THE MAJORITY OF OUTBREAKS IN PIGS." On the genus generally, 55.3: 16 of the top 20 human Salmonella serovars are also isolated from swine, but "HUMAN SALMONELLOSIS IS MORE COMMONLY ACQUIRED IN THE UNITED STATES THROUGH CONSUMPTION OF CONTAMINATED, POORLY COOKED POULTRY PRODUCTS THAN BY CONSUMPTION OF PORK", and S. Choleraesuis is absent from the five commonest swine-associated human serovars, which are S. I 4,[5],12:i:-, Typhimurium, Heidelberg, Agona and Infantis.
How this level was decided
RE-READ AND HELD AT L2 2026-09-04 AGAINST THE REWORDED LABELS. ch55 55.3: the non-Kunzendorf variety "IS A CAUSE OF HUMAN DISEASE IN OTHER COUNTRIES", and Salmonella from pork is an established foodborne route with cooking and hygiene as its control points. Rarely reported for this serovar in the US, which is level 2.
PREVIOUS ANSWER, kept because the evidence behind it has not changed, only the level boundary: Level 2, and the split between the two varieties is what decides it. The variety that causes almost all US swine outbreaks, Kunzendorf, is NOT a common human pathogen here; the variety that causes human disease is the non-Kunzendorf one, and it does so elsewhere. So human infection from US pigs with this serovar is plausible -- it is a Salmonella, the foodborne route exists, and cooking and hygiene are the control points -- but rarely reported, which is the level 2 label. NOTE WHY THIS ENTRY SCORES BELOW ITS OWN GENUS: the enteric salmonellosis entry carries the serovars that actually make Americans ill, and this entry is the host-adapted septicaemic one. Scoring the genus reputation here would double-count what that entry already holds.
C2 Zoonotic impact
Severity of human illness caused by the agent
Severe: Infection carries a substantial risk of life-threatening illness, death, or permanent disability, even if human infections are uncommon
Basis. ch55 55.3: "Non-typhoidal human salmonellosis usually manifests as SELF-LIMITING DIARRHEA, abdominal cramps, vomiting, and fever... AN EXCEPTION IS THE DISEASE CAUSED BY THE NON-KUNZENDORF VARIETY OF S. CHOLERAESUIS THAT CONSISTENTLY PRODUCES SEVERE SEPTICEMIC DISEASE. MORTALITY MAY RESULT FROM DEHYDRATION OR THE EFFECTS OF SEPTICEMIC DISEASE." Also: "In a low percentage of affected individuals, SEPTICEMIC DISEASE DEVELOPS, LEADING TO OSTEOMYELITIS, PNEUMONIA, OR MENINGITIS THAT REQUIRE ANTIBIOTIC THERAPY."
How this level was decided
Level 4, and it is scored on the chapter naming this serovar as THE EXCEPTION to the mild rule. Almost all non-typhoidal salmonellosis is a self-limiting diarrhoea and the chapter says so; S. Choleraesuis is singled out as consistently producing severe septicaemic disease, with mortality. The level 4 label asks for a substantial risk of life-threatening illness EVEN IF HUMAN INFECTIONS ARE UNCOMMON, and that clause is doing the work here -- C1 is level 2 because it rarely happens from US pigs, and C2 is level 4 because when it does happen the illness is septicaemia rather than gastroenteritis. THE PAIR LOOKS ODD IN A TABLE AND IS CORRECT, in the same way rabies is C1 level 2 and C2 level 4.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Routine biosecurity keeps it out: Quarantine of incoming stock, transport and fomite control, cleaning and disinfection, and the usual monitoring reliably exclude it
Basis. ch55 55.8.1: "Although COLONIZATION OF PIGS WITH SALMONELLA IS DIFFICULT TO AVOID, PREVENTION OF DISEASE IS ACHIEVABLE by minimizing Salmonella exposure while maximizing pig resistance. SALMONELLA EXPOSURE CAN BE REDUCED WITH DILIGENT ENVIRONMENTAL CONTROL AND SANITATION PROCEDURES OF THE FARM FACILITIES, EQUIPMENT, AND TRANSPORT VEHICLES, AS WELL AS THE USE OF UNCONTAMINATED FEED and discouraging the practice of commingling varying ages and populations of pigs... a comprehensive biosecurity plan should include QUARANTINING OF NEW BREEDER STOCK, LIMITING VISITOR ACCESS, DECONTAMINATION OR CHANGING OF FOOTWEAR, RODENT AND INSECT CONTROL PROCEDURES, AND BIRD AND WILDLIFE PROOFING TO PREVENT FARM-TO-FARM SPREAD." 55.6.2: "S. Choleraesuis is classified as A HOST-ADAPTED SEROVAR", and "THE PRESENCE OF S. CHOLERAESUIS IN US SWINE HERDS HAS BEEN VARIABLE OVER THE LAST CENTURY but continues to be a frequent disease-causing serovar in swine globally."
How this level was decided
Level 3, and it is the worked example at this level. The chapter's prevention list is the level 3 list item for item -- quarantine of incoming stock, transport and fomite control, cleaning and disinfection, rodent and wildlife exclusion, clean feed. THE HOST-ADAPTED CLASSIFICATION IS WHAT MAKES LEVEL 3 RIGHT RATHER THAN LEVEL 1, and it is the distinction between this entry and the enteric salmonellosis entry: the generalist serovars are everywhere and colonisation is difficult to avoid, but S. Choleraesuis is adapted to pigs, its US presence has been VARIABLE over a century, and a herd can be without it. An agent whose prevalence rises and falls is one that is being kept out and let in.
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. ch55 55.7: "Clinical signs and lesions may lead to A PRESUMPTIVE DIAGNOSIS of salmonellosis but ARE INSUFFICIENT FOR CONFIRMATION given the number of other diseases that resemble the various forms of salmonellosis... The clinical signs and gross lesions observed with S. Choleraesuis septicemia ARE SIMILAR TO THOSE OF OTHER BACTERIAL SEPTICEMIAS such as Erysipelothrix rhusiopathiae, Streptococcus suis, Actinobacillus pleuropneumoniae, and Actinobacillus suis, BUT ALSO CLASSICAL SWINE FEVER AND AFRICAN SWINE FEVER. Gross lesions of splenomegaly, hepatomegaly, lymphadenomegaly, interstitial pneumonia, and multifocal hepatic necrosis altogether are VERY SUGGESTIVE of septicemia by S. Choleraesuis but are not seen in every case and MAY CLOSELY RESEMBLE LESIONS OF CLASSICAL SWINE FEVER. A definitive diagnosis of clinical salmonellosis requires alignment of clinical signs, gross and histological lesions, ISOLATION OF SALMONELLA BY BACTERIAL CULTURE, AND IDENTIFICATION OF THE SEROVAR." The trap: "THE WIDE DISTRIBUTION OF ENVIRONMENTAL SALMONELLAE AND THE INCIDENCE OF SUBCLINICAL INFECTION AND SHEDDING of various serovars MAKES CULTURE OR DETECTION OF SALMONELLA SPP. IN INTESTINAL LESIONS OR CONTENTS ALONE UNRELIABLE FOR DISEASE DIAGNOSIS."
How this level was decided
Level 2. The presentation is a bacterial septicaemia that looks like five other bacterial septicaemias and, importantly, like classical swine fever, so it is not level 1; and confirmation is culture plus serotyping, which every regional veterinary diagnostic laboratory does routinely. That is the level 2 label. NOTE THE ONE ITEM THAT BELONGS IN A BRIEF AND IN A FOREIGN-ANIMAL-DISEASE CONTEXT: the chapter twice says these lesions resemble classical swine fever, and once adds African swine fever. A septicaemic finisher pig with a big spleen and hepatic necrosis is a differential that includes two reportable diseases.
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
Basis. ch55 55.6.2: "The most common presentation of S. Choleraesuis is A SEPTICEMIC DISEASE AFFECTING MULTIPLE ORGANS... Clinical infection is most often observed in weaned pigs less than 5 months of age, more commonly between 6 and 16 weeks of age... IN MOST OUTBREAKS, THE CASE FATALITY RATE IS HIGH, ESPECIALLY IN YOUNGER PIGS, WHILE MORBIDITY IS VARIABLE BUT IS USUALLY LESS THAN 10%. THE DURATION OF THE DISEASE IN INDIVIDUAL PIGS, AS WELL AS THE DURATION AND SEVERITY OF EACH EPIDEMIC, IS UNPREDICTABLE BUT WILL BE PROLONGED WITHOUT SUCCESSFUL INTERVENTION. In pregnant sows, abortions may occur."
How this level was decided
Level 3 -- losses that measurably increase cost of production but remain manageable within normal farm operations. THE TWO NUMBERS TOGETHER ARE WHAT SET THE LEVEL, and they pull against each other: case fatality is high, but morbidity is usually under 10%. A tenth of a nursery group with a high death rate, over a prolonged and unpredictable epidemic, is a serious and measurable loss that a unit absorbs -- not the whole-herd event that level 4 describes. NOT LEVEL 4: unlike African swine fever or Streptococcus zooepidemicus, most of the pigs do not get sick. NOT LEVEL 2: the losses are deaths and abortions over months, not a short-lived scour.
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, uncommon disease at the moment though it does seem to cycle every few decades, regardless market has not and will not react, it is highly pig adapted"
Basis. S. Choleraesuis has been present in US swine herds for over a century, variably (ch55 55.6.2), and is a frequent disease-causing serovar in swine globally. No trade measure, movement restriction or consumer response to a S. Choleraesuis diagnosis in pigs is recorded anywhere in the chapter, which discusses Salmonella market questions entirely in terms of foodborne human illness attributed to other serovars.
How this level was decided
INFERRED. Level 1 under the standing note SCORING/market_impact: an agent long present and routinely diagnosed in US pigs with no market move ever observed, so the absence is an observation. NOTE THE ARGUMENT AGAINST AND WHY IT FAILS: Salmonella as a genus is a live consumer-facing issue and the chapter prices US human salmonellosis at $4.1 billion a year. But it also says pork is a less common source than poultry, and that this serovar is not among the five swine-associated serovars causing human illness here. The market risk in that paragraph belongs to the enteric salmonellosis entry, not this one.
C7 Treatment potential
Potential for treatment to improve outcomes
Some: Treatment exists but is inconsistent, requires extralabel use, or works only in some circumstances
Basis. ch55 55.8.2: "A salmonellosis diagnosis of clinically ill pigs WARRANTS IMMEDIATE TREATMENT, typically supportive therapy, and antimicrobial intervention... VIGOROUS THERAPY EARLY IN THE COURSE OF SEPTICEMIA CAUSED BY S. CHOLERAESUIS WAS REPORTED TO SIGNIFICANTLY REDUCE THE DURATION AND SEVERITY OF THE DISEASE (Jacks et al. 1981)." The qualifications: "Unfortunately, THE ABILITY OF SALMONELLA TO INHABIT PROTECTED INTRACELLULAR NICHES IN THE HOST CAN HINDER THE ACCESSIBILITY OF MANY ANTIMICROBIALS during clinical disease. Furthermore, 10-20% OF SALMONELLA ARE RESISTANT TO ONE OR MORE ANTIBIOTICS, emphasizing the need for data-based decision-making using antibiotic sensitivity testing... treatment with injectable antibiotics may be necessary IF PIGS ARE TOO ILL TO CONSUME SUFFICIENT MEDICATION by feed or water routes."
How this level was decided
Level 2. Treatment exists and works when given early -- the chapter cites a controlled reduction in duration and severity -- but it works only in some circumstances, which is the level 2 clause and which the chapter states three ways: the organism hides intracellularly where drugs do not reach, a fifth of isolates are resistant to something, and the sick pig will not eat or drink so mass medication misses the animals that need it most. NOT LEVEL 1: a septicaemic pig treated late is not an acceptable recovery, and the chapter's own framing is that early vigorous therapy REDUCES duration and severity rather than curing.
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. ch55 55.8.1: "VACCINATION WITH ATTENUATED, LIVE VACCINES THAT STIMULATE CELL-MEDIATED IMMUNITY IS A PREVENTION STRATEGY THAT HAS BEEN EFFICACIOUS AGAINST SYSTEMIC DISEASE CAUSED BY S. CHOLERAESUIS and has also shown effectiveness against enterocolitis due to S. Typhimurium... IN NORTH AMERICA, VACCINATION AGAINST S. CHOLERAESUIS WAS CREDITED WITH A MAJOR REDUCTION IN THE OCCURRENCE OF SYSTEMIC SALMONELLOSIS... WHEN GIVEN AT WEANING, VACCINATION PROTECTED PIGS FOR AT LEAST 20 WEEKS AGAINST HOMOLOGOUS SEROTYPES, WITH SOME CROSS-PROTECTION SUGGESTED WITH HETEROLOGOUS SEROTYPES. A vaccine containing both S. Choleraesuis and S. Typhimurium is also available." Historically an attenuated live S. Choleraesuis vaccine "WAS WIDELY USED IN THE UNITED KINGDOM for many years BUT WAS WITHDRAWN WHEN S. CHOLERAESUIS DISEASE DECREASED TO NEGLIGIBLE PROPORTIONS."
How this level was decided
Level 1 on the first half of the label -- effective vaccines are widely available in the US. This is the strongest C8 evidence in batch B and it is historical rather than experimental: the attenuated live vaccine is credited with a MAJOR REDUCTION in North American systemic salmonellosis, protection lasts at least twenty weeks from a single dose at weaning, a combination product exists, and in the United Kingdom the vaccine worked so well it was withdrawn for want of disease. NOT LEVEL 2, and the contrast with the other bacterins in this register is the point: this one protects for the whole grow-out and showed some heterologous cross-protection, where the Glaesserella, Actinobacillus and Leptospira products do not.
Levels and evidence are generated from data/assignments/salmonella_choleraesuis.yml; the overview is authored in data/overviews/salmonella_choleraesuis.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.