Exudative Epidermitis
LEVELS: Highly unlikely; Mild; Already in the herd; Routine; Moderate; Negligible; Some; Available but inconsistent
| Register id | staphylococcus_hyicus |
| Type | bacteria |
| Scientific name | Staphylococcus hyicus |
| NCBI taxid | 1284 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Staphylococcus hyicus causes exudative epidermitis, universally known as greasy pig disease. Toxigenic strains produce exfoliative toxins that split the skin just below the surface, and affected piglets — most often between three and 32 days old — develop patches of red, moist, glistening skin that spread rapidly and dry into a thick brown greasy crust. There is no itching. In severe cases the pig dies of dehydration within a day or two. Four things have to coincide for an outbreak: a toxigenic strain present, insufficient maternal immunity, some breach of the skin from fighting, abrasion or another infection, and the right environmental conditions. The organism itself is normal skin flora on adult pigs in most herds, so it is not something to be kept out. Outbreaks tend to be self-limiting over two to three months as the sows develop immunity. A milder localised form occurs in older pigs. Control combines early antimicrobial treatment, autogenous sow vaccination, reducing skin trauma and improving the environment.
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. "c1l1, highly pig adapted, though isolated from humans rarely it is misleading to consider it a consequential zoonosis"
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.2, a Public Health section of its own and one sentence long: "STAPHYLOCOCCUS HYICUS IS AN INFREQUENT CAUSE OF DISEASE IN HUMANS; HOWEVER, REPORTS INDICATE S. HYICUS CAN CAUSE WOUND INFECTIONS, BACTEREMIA, SPONDYLODISCITIS, AND ENDOCARDITIS (Foissac et al. 2016; Kirk et al. 2022; Osterlund and Nordlund 1997)." On where the organism lives, 56.2.3: "S. hyicus is considered NORMAL BACTERIAL FLORA ON THE SKIN OF ADULT SWINE"; it "has been isolated from cattle, goats, horses, and chickens", but "THESE ANIMAL SPECIES ARE NOT CONSIDERED SOURCES OF S. HYICUS FOR PIGS" and species-specific differences make those strains incapable of causing disease in pigs. NONE OF THE THREE HUMAN REPORTS IS ATTRIBUTED TO A PIG in the chapter.
How this level was decided
MOVED L2 -> L1, 2026-09-04, and this brings the pass into line with a ruling Eric already made. The reworded level 1 covers an agent "reported but not attributed to pig or pork exposure", which is exactly what he said on 2026-09-03: "though isolated from humans rarely IT IS MISLEADING TO CONSIDER IT A CONSEQUENTIAL ZOONOSIS." His correction had been publishing level 1 over a pass answer of level 2 ever since. Nothing published changes here.
PREVIOUS ANSWER: Level 2, and FLAGGED so it is ruled consistently with actinobacillus_suis, which is the same shape of evidence and which you put at LEVEL 1 earlier today. THE SHAPE: human disease with the organism is on record; a link attributing pigs as the source is not. THE DIFFERENCE, AND IT IS WHY I HAVE NOT SIMPLY COPIED THAT RULING: S. hyicus is unambiguously a pig-adapted organism -- the chapter calls it normal flora of swine skin and says the strains carried by cattle, goats, horses and chickens are a different thing -- and there are three independent human reports across twenty-five years, not one ambiguous isolate shared between two species. Human infection from pigs is plausible and has rarely been reported, with no control point implemented against it, which is the level 2 label. IF YOU READ IT AS YOU READ A. SUIS -- no attribution, so level 1 -- then C2 below must go to level 1 with it, because C1 level 1 implies C2 level 1 and validate_criteria.py checks it.
C2 Zoonotic impact
Severity of human illness caused by the agent
Mild: Human illness is usually mild and self-limiting, and serious disease occurs only rarely
Corrected by Eric from L3 Moderate. Reason: MOVED TO LEVEL 2, 2026-09-04. His markup: "s.hyicus c2l2". The pass had scored level 3 on the conditions the folder names -- bacteraemia, spondylodiscitis and endocarditis, all hospital admissions -- and he brings it down one. THE MOVE FOLLOWS HIS OWN S. AUREUS RULE, given on 2026-09-02 for the neighbouring entry: "not all S.aureus are drug resistant so need to avoid the temptation to put this as l4. l3 is suitable for a more general risk rating." The same discipline applied here says the severe presentations are the reported ones because they are the ones worth reporting, and the general case is milder. It also sits consistently with his 2026-09-03 view of the organism, "though isolated from humans rarely IT IS MISLEADING TO CONSIDER IT A CONSEQUENTIAL ZOONOSIS" -- which now lives in C1 at level 1, while C2 records that the illness, when it happens, is usually mild.
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.2 names the human conditions and nothing else -- no incidence, no outcome, no case fatality: "reports indicate S. hyicus can cause WOUND INFECTIONS, BACTEREMIA, SPONDYLODISCITIS, AND ENDOCARDITIS." The chapter's framing of frequency is "AN INFREQUENT CAUSE OF DISEASE IN HUMANS".
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. The previous assessment scored level 3 and was overruled to 1 on the pig-attribution reading, which is now C1's business. Its words: "bacteraemia, spondylodiscitis and endocarditis are all hospital admissions".
PREVIOUS ANSWER, written under the pig-attribution reading: INFERRED, AND FLAGGED WITH C1. LEVEL 3 IS SCORED on the conditions named rather than on any outcome data, because there is none: bacteraemia, spondylodiscitis and endocarditis are all hospital admissions, and spondylodiscitis in particular is a weeks-to-months course of intravenous antibiotics. Clinically important illness requiring hospitalization, with death or permanent disability not established, is the level 3 label. THE ARGUMENT FOR LEVEL 4 is that endocarditis carries substantial mortality in any organism and spondylodiscitis can leave permanent neurological deficit, and the level 4 label asks only for a substantial risk of that EVEN IF INFECTIONS ARE UNCOMMON. THE ARGUMENT FOR LEVEL 2 is that a wound infection is the commonest of the four and is mild. I have not taken either, because the folder supports the list of conditions and supports nothing about how they ended. NOTE THE DEPENDENCY: if C1 goes to level 1, this cell goes to level 1 with it, not to level 2.
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. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.3: "Staphylococcus hyicus is distributed globally and INFECTS MOST PIG HERDS. In the United States, it was reported to cause sickness or mortality in 33.5% of sites with nursery-age pigs (USDA 2016). S. HYICUS IS CONSIDERED NORMAL BACTERIAL FLORA ON THE SKIN OF ADULT SWINE and is present in many herds without causing disease. It can be recovered from multiple skin sites on healthy pigs... INFECTED PIGS ARE THE NEARLY EXCLUSIVE SOURCE OF INFECTION for uninfected individuals and herds... Transmission is primarily by direct contact and can be lateral, between pigs in the same cohort, or VERTICAL, BY CONTACT OF SUCKLING PIGS WITH THEIR INFECTED DAM. Vertical transmission may also occur AT BIRTH AS PIGS CONTACT S. HYICUS WHILE TRANSITING AN INFECTED VAGINA. S. hyicus strains isolated from the skin of piglets WITHIN 24 HOURS AFTER BIRTH were the same type as their dams."
How this level was decided
Level 1, and it is the worked example at this level in criteria_levels.yml. The chapter states the label rather than implying it: present in most herds, normal flora of adult swine skin, and acquired by the piglet from its dam in the birth canal within twenty-four hours of birth. There is no introduction event to prevent. Scored level with Streptococcus suis, Glaesserella parasuis and neonatal E. coli, the other worked examples here, and for the same reason -- the pig brings it.
C4 Detection difficulty
Difficulty of recognizing and confirming infection
Routine: The disease would be suspected from clinical signs, history and epidemiology in normal practice, and confirmed by tests that local or regional laboratories run routinely
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.7: "CLINICAL SIGNS AND LESIONS ARE CHARACTERISTIC IF NOT PATHOGNOMONIC FOR EE IN YOUNG PIGLETS. Diagnosis of EE in adults or animals with local lesions secondary to trauma is more difficult. Confirmation requires demonstration of typical microscopic lesions and ISOLATION OF S. HYICUS... S. HYICUS GROWS WELL ON SHEEP OR BOVINE BLOOD AGAR... S. hyicus can be identified by using CONVENTIONAL BIOCHEMICAL TESTS OR PANEL IDENTIFICATION SYSTEMS OR BY MALDI-TOF." The chapter then works through the differential -- swinepox, mange, ringworm, pityriasis rosea, zinc deficiency parakeratosis, dermatosis vegetans -- and separates each on gross appearance. The one thing that is NOT routine is strain typing: "TESTS FOR TOXIN IDENTIFICATION ARE NOT IN WIDESPREAD USE IN VETERINARY DIAGNOSTIC LABORATORIES."
How this level was decided
Level 1. Both halves of the label hold at the high end: greasy pig disease in a three-week-old litter is recognised on sight -- the chapter says characteristic if not pathognomonic -- and confirmation is culture on ordinary blood agar with routine biochemistry or MALDI-TOF at any regional laboratory. NOTE WHAT THE UNAVAILABLE TEST IS AND WHY IT DOES NOT LOWER THE LEVEL: toxin profiling and phage typing separate virulent from avirulent strains, and those are not in routine use. But both toxigenic and non-toxigenic strains can be isolated from the same lesion, so typing answers a research question about the isolate rather than the diagnostic question about the pig. C4 asks about recognizing and confirming infection.
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. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.3 gives a US-specific figure, which this criterion rarely gets: "In the United States, it was reported to CAUSE SICKNESS OR MORTALITY IN 33.5% OF SITES WITH NURSERY-AGE PIGS (USDA 2016)." On severity where it occurs, 56.2: "Affected pigs FAIL TO THRIVE, and loss of body fluid may lead to DEHYDRATION AND DEATH." 56.2.3: "ENTIRE LITTERS OR COHORTS MAY BE AFFECTED WITH HIGH MORTALITY... Outbreaks are usually self-limiting and GENERALLY LAST 2-3 MONTHS BUT MAY PERSIST FOR 12-18 MONTHS." 56.2.5: "Pigs can die within 24-48 hours... Death usually follows in 3-10 days", and in the milder weaned form "AFFECTED PIGS SUFFER REDUCED WEIGHT GAINS RELATIVE TO PEERS... recovery may require several weeks." 56.2.3 also names where it bites hardest in modern production: "EE is observed MORE FREQUENTLY IN PIGLETS BORN TO GILTS IN START-UP HERDS or born to gilts introduced to an infected herd or environment WITHOUT ADEQUATE TIME TO DEVELOP IMMUNITY prior to farrowing."
How this level was decided
Level 3. The standing note SCORING/production_cost_impact says score modern US production rather than the chapter, and here the chapter hands over a modern US number: a third of US nursery sites reported sickness or mortality from this organism. What follows is measurable and continuous -- dead suckling piglets, weeks of lost gain in the weaned form, antimicrobial and labour cost, and outbreaks that run for two to three months and occasionally for a year and a half -- and it is absorbed within normal farm operations, which is the level 3 label including its "chronic, or associated with endemic disease" clause. NOT LEVEL 4: outbreaks are self-limiting, most herds carry the organism without disease, and there is no suggestion of an unsustainable increase in cost of production. NOT LEVEL 2: 33.5% of nursery sites is not a small or short-lived loss, and the gilt-litter concentration means the losses land on the herds least able to absorb them.
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, no market impact"
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. S. hyicus is distributed globally, infects most pig herds and was reported at 33.5% of US nursery sites (ch56 56.2.3). No trade measure, movement restriction or consumer response to exudative epidermitis is recorded anywhere in the chapter.
How this level was decided
INFERRED. Level 1 under the standing note SCORING/market_impact: an organism endemic and routinely diagnosed in US pigs for decades, with no market move ever observed. The disease is a skin condition of suckling pigs that never reaches a carcass a consumer sees.
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. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.8: "EARLY TREATMENT following onset of disease provides the best chance of success, BUT SEVERELY AFFECTED ANIMALS MAY NOT RESPOND. Antimicrobial drugs are commonly used to treat EE. HOWEVER, REPORTS INDICATE S. HYICUS IS RESISTANT TO MANY ANTIMICROBIAL AGENTS... Although regional differences exist, RESISTANCE TO PENICILLIN, ERYTHROMYCIN, STREPTOMYCIN, SULFONAMIDES, AND TETRACYCLINE IS A FREQUENT OCCURRENCE. In addition, genetic elements conferring METHICILLIN AND ZINC RESISTANCE have been reported... THEREFORE, ANTIMICROBIAL SUSCEPTIBILITY TESTING of isolates recovered from EE lesions IS RECOMMENDED. In the absence of drug susceptibility results, ceftiofur, enrofloxacin, or a combination of trimethoprim/sulfamethoxazole and lincomycin are best choices." Supportive care matters as much as the drug: "FLUID AND ELECTROLYTE REPLACEMENT IS IMPORTANT in severely affected piglets."
How this level was decided
Level 2, and it is the worked example at this level in criteria_levels.yml, alongside Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae. The chapter gives the level 2 clause three separate ways: treatment must be early or it fails, severely affected animals may not respond at all, and resistance to five common drug classes is frequent enough that the chapter tells you to culture and test before choosing. Treatment exists and works only in some circumstances. Level 1 would say animals recover acceptably, and the piglet dying of fluid loss in forty-eight hours does not.
C8 Vaccine availability
Availability of effective vaccines or bacterins
Available but inconsistent: Commercial or autogenous vaccines exist in the US but protection may be inconsistent
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch56, and exudative epidermitis is section 56.2 -- about four pages. The CFSPH MRSA factsheet sits in the staphylococcus_aureus folder, not this one. ch56 56.2.8: "AUTOGENOUS VACCINATION USING STRAINS ISOLATED FROM THE AFFECTED HERD HAS BEEN SHOWN TO REDUCE ANTIBIOTIC USE, MORBIDITY, AND MORTALITY due to S. hyicus (Arsenakis et al. 2018). In newly acquired sows or gilts, VACCINATION PRIOR TO FARROWING WILL PROVIDE SOME COLOSTRAL PROTECTION to offspring and help ward off severe forms of EE." No commercial product is named. The reason autogenous product is the form it takes is in 56.2.1 and 56.2.3: strains vary in virulence, at least six different exfoliative toxins are described, "THERE WAS NO CLEAR PATTERN AS TO WHICH TOXINS ARE MOST COMMON in strains causing EE, AND REGIONAL DIFFERENCES APPARENTLY EXIST."
How this level was decided
Level 2, and this entry shows why the level exists. Product is available in the US -- autogenous bacterins are made from the herd's own isolate and are routinely used against EE -- and there is a published demonstration that they reduce morbidity, mortality and antibiotic use, so this is not level 3. But protection is inconsistent by construction: the vaccine is herd-specific because the toxin repertoire varies between strains and regions with no dominant pattern, and what pre-farrow vaccination buys is stated as "SOME colostral protection" and warding off the SEVERE forms rather than preventing disease. Available but protection may be inconsistent is the level 2 label. NOT LEVEL 1 ON THE "NOT NEEDED" CLAUSE, and the standing note written on 2026-09-03 is the test: a third of US nursery sites report sickness or mortality, so none of its four routes to no-imperative applies here.
Levels and evidence are generated from data/assignments/staphylococcus_hyicus.yml; the overview is authored in data/overviews/staphylococcus_hyicus.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.