Demodectic mange
LEVELS: Highly unlikely; No human illness; Already in the herd; Laboratory-dependent; Negligible; Negligible; Some; Available, or not needed
| Register id | demodex_phylloides |
| Type | parasite |
| Scientific name | Demodex phylloides |
| Evidence | 2 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Demodex phylloides is the follicular mite of pigs, and the chapter's own verdict is that demodectic mange is relatively unimportant in swine even though it is quite common in the subclinical form — Demodex mites are thought to be normal skin flora in mammals generally. The mite spends its entire life inside hair follicles, spreading to neighbouring follicles by crawling from one to the next, and passes between animals only by very close contact, probably from dam to piglet while nursing or huddling; it dies within an hour or so off the host. Because mites are present in nearly all pigs, finding a few of them does not make a diagnosis: it takes deep skin scrapings showing numerous mites, evidence of an actively growing population, and visible lesions together. The lesions begin as red pinpoint foci and become hyperkeratotic nodules that express thick white material when cut, and they can be confused with swinepox. No acaricide has ever been reported to treat swine demodicosis successfully — ivermectin and amitraz work in dogs but not, so far as anyone has published, in pigs — so the chapter's only suggestion is to cull severely affected animals. Transmission between species, including to people, is very unlikely.
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. cfsph_2012_acariasis states it directly: "Among the Demodecidae, DEMODEX IS THE ONLY GENUS IMPORTANT IN DOMESTICATED ANIMALS. DEMODEX MITES ARE VERY HOST SPECIFIC, AND TRANSMISSION BETWEEN SPECIES, INCLUDING ZOONOTIC TRANSMISSION, IS VERY UNLIKELY." And on the mechanism of that specificity: "They are very host specific, and are TRANSMITTED BY VERY CLOSE CONTACT. TRANSMISSION IS PROBABLY FROM THE DAM TO THE NEONATE. Demodex spp. are killed quickly by desiccation (45-60 minutes at 20 degrees C and 40% humidity), and thus are UNLIKELY TO SURVIVE OFF THE HOST FOR MORE THAN A FEW HOURS." ch59 59.3 adds that D. phylloides "spends its entire life inside hair follicles".
How this level was decided
Level 1. The folder answers the criterion in one sentence -- zoonotic transmission is very unlikely -- and gives the reason rather than merely asserting it: the mite lives its whole life inside a hair follicle, moves only by crawling between neighbouring follicles or from dam to neonate at very close contact, and dies within an hour off the skin. There is no route to a person even in principle. NOTE THE CONTRAST WITH SARCOPTES IN THE SAME FOLDER, which is what makes this a clean level 1 rather than a silence: the same factsheet names Sarcoptes var. suis among the zoonotic varieties and says human infestation happens, and about Demodex it says the opposite. The author considered the question for both.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. No human illness with Demodex phylloides is described anywhere in the folder. cfsph_2012_acariasis: "Demodex mites are very host specific, and TRANSMISSION BETWEEN SPECIES, INCLUDING ZOONOTIC TRANSMISSION, IS VERY UNLIKELY."
How this level was decided
Level 1, following C1. Under C2 as rescoped, level 1 means pigs are not a source of human illness with this agent, which is what the factsheet states.
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. ch59 59.3: "Demodectic mange (demodicosis, follicular mange) is relatively unimportant in swine, although IT IS QUITE COMMON IN THE SUBCLINICAL FORM, AS DEMODEX MITES ARE THOUGHT TO BE NORMAL SKIN FLORA IN MAMMALS... Neighboring follicles are colonized by mites crawling out of one follicle and into another. TRANSMISSION OF THE MITES PROBABLY OCCURS BY DIRECT CONTACT WITH NEONATES WHILE NURSING OR HUDDLING." 59.3.1: "BECAUSE MITES ARE PRESENT IN NEARLY ALL SWINE, identification of a few mites does not necessarily prompt a diagnosis of demodicosis." cfsph_2012_acariasis: "Transmission is probably FROM THE DAM TO THE NEONATE."
How this level was decided
Level 1, and the folder states the level rather than implying it. The mites are present in nearly all swine and pass from the sow to the piglet at nursing, so they are carried by the pigs themselves and there is no introduction event to prevent -- the level 1 label word for word. THIS IS THE ONE CELL IN THE BATCH WHERE THE ANSWER IS NOT A JUDGMENT AT ALL: an agent that is normal skin flora cannot be excluded and does not need to be.
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. ch59 59.3.1: "The diagnosis of demodicosis is made by FINDING NUMEROUS MITES IN DEEP SKIN SCRAPINGS. Plucked hair may also reveal mites. BECAUSE MITES ARE PRESENT IN NEARLY ALL SWINE, IDENTIFICATION OF A FEW MITES DOES NOT NECESSARILY PROMPT A DIAGNOSIS OF DEMODICOSIS. A CORRELATION BETWEEN THE PRESENCE OF THE MITES, INDICATIONS OF AN ACTIVELY GROWING POPULATION OF MITES (I.E. A LARGE NUMBER OF IMMATURE STAGES IN THE FOLLICLES), AND VISIBLE LESIONS MUST BE SEEN TO JUSTIFY THE DIAGNOSIS of clinical demodicosis." On the presentation, 59.3: early lesions are red pinpoint foci, older ones hyperkeratotic nodules that express thick white caseous material when incised, and "SUCH LESIONS MAY BE CONFUSED WITH SWINE POX".
How this level was decided
Level 2. The presentation does not point at this disease -- the chapter says the nodules are confused with swine pox, and demodicosis is uncommon enough clinically that nobody reaches for it first -- so this is not level 1. Confirmation is a deep skin scraping or plucked hair read at any practice or regional laboratory, which is the level 2 label. NOTE THE INTERPRETIVE TRAP, WHICH IS THE REAL DIFFICULTY HERE AND IS UNUSUAL IN THIS CRITERION: finding the organism does not make the diagnosis, because nearly every pig carries it. The diagnosis requires judging that the mite POPULATION is actively growing -- counting immature stages in the follicles -- alongside visible lesions. The test is routine; reading it is not.
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, virtually a theoretical risk because the disease is so rare but l1 is correct"
Basis. ch59 59.3, the chapter's own summary judgment in its opening sentence: "DEMODECTIC MANGE (DEMODICOSIS, FOLLICULAR MANGE) IS RELATIVELY UNIMPORTANT IN SWINE, ALTHOUGH IT IS QUITE COMMON IN THE SUBCLINICAL FORM." No economic figure, growth-rate effect, mortality or carcass consequence is given anywhere for demodicosis -- in a chapter that quantifies sarcoptic mange at 4.5-12% reduced growth and discusses lice-associated anaemia. The only loss implied is the disposal of individuals: 59.3.2, "it may be prudent to CULL SEVERELY INFECTED PIGS."
How this level was decided
INFERRED. Level 1, on the chapter's explicit ranking of the disease rather than on silence -- "relatively unimportant in swine" is a judgment the authors made, in a section they wrote immediately after quantifying sarcoptic mange, so the absence of numbers here is a finding rather than a gap. THE ARGUMENT FOR LEVEL 2 is that clinical cases do occur, produce nodular skin lesions, and end in culling the affected pig, which is not literally no measurable effect. It is not taken, because those cases are sporadic individuals in a herd where nearly every animal carries the mite subclinically, and nothing in the folder suggests a herd-level cost of any size.
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 effect on the market"
Basis. Demodex mites are normal skin flora of nearly all swine worldwide (ch59 59.3), and no trade measure, movement restriction or market response to demodicosis is recorded anywhere in the folder.
How this level was decided
INFERRED. Level 1 under the standing note SCORING/market_impact: an organism universally present in US pigs, with no market move ever observed. There is no prospect of one for a mite that every pig already carries.
C7 Treatment potential
Potential for treatment to improve outcomes
Some: Treatment exists but is inconsistent, requires extralabel use, or works only in some circumstances
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c7l2, extralable treatment expected to be efficacious"
Basis. ch59 59.3.2, in its entirety: "THERE ARE NO REPORTS OF SUCCESSFUL TREATMENT OF SWINE DEMODICOSIS WITH ANY ACARICIDE. IVERMECTIN OR AMITRAZ ARE SUCCESSFUL IN CANINE DEMODICOSIS. In dogs, there is a genetic predisposition to clinical demodicosis. WHILE NOT PROVEN IN SWINE, IT MAY BE PRUDENT TO CULL SEVERELY INFECTED PIGS." Against that, 59.3 rates the disease "relatively unimportant in swine", and the same chapter records that ivermectin and amitraz are highly effective against the OTHER mange mite of pigs.
How this level was decided
FLAGGED, AND THE HARDEST CELL IN THE BATCH -- three levels are defensible and the folder does not choose between them. LEVEL 2 IS SCORED, on your Globocephalus and Echinococcus reasoning: products exist and would be used extralabel, ivermectin and amitraz cure the same condition in dogs, and no swine label names demodicosis -- "treatment exists but is inconsistent, requires extralabel use, or works only in some circumstances". THE ARGUMENT FOR LEVEL 3 is the chapter's flat sentence that no acaricide has ever been reported to treat this successfully in a pig, which is stronger than inconsistent; if you read that as no effective treatment existing, and the culling of severely affected pigs as an outcome worth improving, it is level 3. THE ARGUMENT FOR LEVEL 1 is that the disease is "relatively unimportant" and mostly subclinical, so almost nothing would improve. THAT LAST READING IS THE ONE I WOULD RESIST, because your Trichinella/MAC boundary turns level 1 on EXCLUDABILITY -- and this agent cannot be excluded at all, it is normal skin flora, which is the side of your boundary where an absent treatment is a real gap.
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, no clinical or market impnerative for a vaccine"
Basis. No vaccine against Demodex is mentioned anywhere in the folder and no vaccine research is referred to. ch59 59.3: demodicosis "IS RELATIVELY UNIMPORTANT IN SWINE, ALTHOUGH IT IS QUITE COMMON IN THE SUBCLINICAL FORM, AS DEMODEX MITES ARE THOUGHT TO BE NORMAL SKIN FLORA IN MAMMALS."
How this level was decided
INFERRED. Level 1 on the "not needed" clause. Under your PCV4 rule the assertion has to be a claim the folder can carry, and here it can: the chapter ranks the disease as relatively unimportant, nearly every pig carries the mite with no consequence, and the clinical form is a sporadic skin condition of individuals. Vaccinating a herd against its own normal skin flora, to prevent a disease the chapter calls unimportant, is not something the agent's clinical or economic weight justifies -- which is the test the 2026-08-28 rewording set for level 3 and this fails. NOTE THE ASYMMETRY WITH C7 ABOVE, since the two look inconsistent side by side and are not: a TREATMENT would have something to act on, because clinical cases exist and end in culling, whereas a VACCINE would have to be given to every pig against a universal commensal to prevent that rare outcome.
Levels and evidence are generated from data/assignments/demodex_phylloides.yml; the overview is authored in data/overviews/demodex_phylloides.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.