Enterococcal diarrhea
LEVELS: Highly unlikely; No human illness; Already in the herd; Laboratory-dependent; Minor; Negligible; Some; Available, or not needed
| Register id | enterococcus_spp |
| Type | bacteria |
| Scientific name | Enterococcus |
| NCBI taxid | 1350 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Enterococci are gram-positive cocci that live normally in the intestine of every pig, and this entry covers the few species — mainly Enterococcus durans, E. villorum and E. hirae — that can attach to the gut lining and cause diarrhoea in piglets between about two and twenty days old. Under the microscope the organisms are seen stuck to the surface of the villi through the jejunum and ileum, which is what distinguishes genuine disease from ordinary carriage. That distinction is the practical difficulty: E. hirae was found in 44% of piglets with diarrhoea and 43% of healthy controls, so isolating it proves very little on its own and diagnosis needs the clinical picture, the microscopic lesion and the culture together. It appears to be growing in importance as a cause of neonatal diarrhoea — it was the second most frequently isolated pathogen in one recent case series — and it is one of the agents implicated in the New Neonatal Porcine Diarrhoea Syndrome described in Scandinavia. It is not a public health concern in this context.
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. "c1l1, this genus/species is important in terms of its involvement in AMR transfer events, but the strains in pigs I agree are not important zoonoses per se"
Basis. Section 58.6 has no public health passage. Its four subsections cover relevance and etiology, epidemiology and pathogenesis, clinical signs, and prevention and control, and none mentions human infection, foodborne risk or occupational exposure. The organisms named are enteroadherent members of the E. faecium species group -- "mainly E. durans, E. villorum, and E. hirae". (ch58 58.6)
How this level was decided
INFERRED, and the inference is from a structured silence rather than a bare absence. Chapter 58 gives an explicit public health passage to every agent that has one -- anthrax, melioidosis, Campylobacter, Chlamydia, Listeria, Mycobacterium, Rhodococcus, Trueperella and Yersinia all carry one, and Treponema pedis is stated to have "no known public health significance". Enterococcus has none, and the species named are the animal-adapted enteroadherent ones rather than the nosocomial E. faecalis and E. faecium sensu stricto. Level 1 is itself a statement about absence of evidence, which is what the folder supports. NOTE: this is a fair cell for Eric to overturn if he judges enterococcal transfer to people to be a real pig-sourced route.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c2l1, this genus/species is important in terms of its involvement in AMR transfer events, but the strains in pigs I agree are not important zoonoses per se"
Basis. No human disease of any kind is described in section 58.6. (ch58 58.6)
How this level was decided
RE-SCORED 2026-09-04. C2 now grades the severity of the illness the agent causes in a person, independent of how the person was exposed -- the 2026-09-01 pig-attribution reading is reversed, and C1 alone carries the source question. FLAG. Enterococci are a major cause of human nosocomial infection, so "does not cause illness in people" is false of the genus, but the folder records no human disease and cannot support a severity level.
PREVIOUS ANSWER, written under the pig-attribution reading: INFERRED, on the same structured silence as C1. C2 says to score level 1 whenever the agent does not cause disease in people, and the folder records none. If Eric moves C1 he will likely want to move this too, since human enterococcal disease in general is serious.
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. "Enterococcus spp. are gram-positive cocci known as normal commensal intestinal flora but also observed as opportunistic pathogens." "detection of E. hirae was common in piglets with diarrhea (44%) and control pigs (43%)." (ch58 58.6.1, 58.6.2)
How this level was decided
A normal commensal of the pig intestine, found at essentially equal rates in healthy and diarrhoeic piglets. There is no introduction event to prevent -- the organism is already carried by the pigs. Level 1.
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, differences of opinion amongst vets and diagnosticians as to the significance of this infection but easy to test for by request"
Basis. "The intestines appear dilated and filled with fluid, similar to diarrhea caused by other common agents of neonatal diarrhea." "Histologically, many gram-positive cocci are adhered to the apical surface of villus enterocytes through the jejunum and ileum." "Diagnosis requires a combination of clinical signs, characteristic microscopic lesions, and bacterial culture results." "its presence in healthy piglets confounds the importance of Enterococcus isolation from the intestinal tract." (ch58 58.6.2, 58.6.3)
How this level was decided
The clinical picture is indistinguishable from every other neonatal diarrhoea, so nothing points at this agent, ruling out level 1. Culture alone does not settle it either, because carriage rates are the same in healthy piglets -- diagnosis needs histopathology showing adherent cocci alongside culture. Both are standard regional veterinary diagnostic laboratory work. Level 2.
C5 Production cost
Financial impact on the infected farm's cost of production
Minor: Small and generally short-lived losses with little effect on overall cost of production
INFERRED — reasoned, not stated. The evidence implies this level rather than stating it. The reasoning is below.
Corrected by Eric from L3 Moderate. Reason: "should be c5l2, there is a small amount of evidence suggesting this agent is emerging as a potential pathogen of young pigs but as it stands today in the US, it only ranks as minor cost and is rarely diagnosed or treated"
Basis. "Such cases of enteroadherent Enterococcus-associated diarrhea have been reported in piglets between approximately 2 and 20 days of age and appear to be of increasing significance as a cause of porcine neonatal diarrhea since first described." "Enteroadherent enterococci were found involved in cases of the New Neonatal Porcine Diarrhea Syndrome (NNPDS) reported in Scandinavian countries." "In a retrospective study by Boulbria et al. (2023), E. hirae was the second most frequently isolated pathogen, detected in 43.4% of cases." (ch58 58.6.1, 58.6.2)
How this level was decided
INFERRED -- the chapter gives no mortality rate and no cost figure. Neonatal diarrhoea affecting whole litters in the first three weeks carries pre-weaning mortality and lasting growth cost, and the chapter describes the condition as increasing in significance and as a named component of NNPDS. That is a measurable increase in cost of production that farms nonetheless manage, which is level 3. Level 2 is the alternative if weight is given to affected piglets continuing to nurse, which suggests a milder course.
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 common in essentially all mammals including humans (though different species/strains) and under normal circumstances, its occurrence or diagnosise would not have an impact on markets"
Basis. The section describes a commensal organism causing sporadic neonatal diarrhoea. It records no trade measure, movement control, export restriction or consumer response.
How this level was decided
INFERRED. A commensal of the pig gut causing pre-weaning diarrhoea has no route to pork supply or demand -- nothing leaves the farm, nothing is reportable, and no consumer dimension exists. Level 1.
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. "Because of the natural resistance of enterococci to some antibacterial agents, antimicrobial susceptibility testing is advised before treatment." "Due to the lack of knowledge about the clinical and epidemiological aspects of this infection, other preventive measures are difficult to recommend." (ch58 58.6.4)
How this level was decided
Treatment is used, so this is not level 3, but the chapter conditions it on susceptibility testing because the genus is intrinsically resistant to several classes. Treatment that works only in some circumstances and requires testing to direct it is level 2.
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, but as with other agents, there is no imperative to build a vaccine due to the low prevalance and clinical significance" 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 58.6.4 states that "other preventive measures are difficult to recommend" and names no vaccine. Eric, 2026-08-27: "there is no imperative to build a vaccine due to the low prevalance and clinical significance".
How this level was decided
MOVED L3 -> L1 by the rewording. His word imperative is the level 3 test in the new wording. A commensal causing sporadic neonatal diarrhoea, which he separately corrected to C5 level 2, does not justify a vaccine. Level 1.
Levels and evidence are generated from data/assignments/enterococcus_spp.yml; the overview is authored in data/overviews/enterococcus_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.