Pig Louse
LEVELS: Highly unlikely; No human illness; Routine biosecurity keeps it out; Routine; Minor; Negligible; Little; Available, or not needed
| Register id | haematopinus_suis |
| Type | parasite |
| Scientific name | Haematopinus suis |
| NCBI taxid | 511927 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Haematopinus suis is the pig louse, the only louse that infests swine and among the largest lice of any species — the females are about 6 mm long and easily seen with the naked eye. It is a sucking louse and the entire life cycle happens on the pig; it is strictly host-specific, so rodents, birds and other pests play no part in introducing it, and it cannot survive more than two or three days off the host. Lice are found all over the body but concentrate on the neck, jowls, flanks and inner legs, and cluster inside the ears. They should always be on the list when pigs are itching, and infestation is confirmed by finding the lice or their nits, which are cemented to the lower part of the hair shafts — that placement distinguishes them from blowfly eggs. The reference chapter is candid that the economic importance of lice has not been evaluated as carefully as that of mange: severe infestation causes anaemia in young pigs and may reduce growth and feed efficiency, with one estimate of 50 g/day lost and other studies finding no effect. Lice have also been considered vectors of swinepox, and hides from lousy pigs may be unusable for high-grade leather. Treatment is by sprays, pour-ons or dusts, repeated after ten days if the product does not kill eggs, and the eradication strategies used for mange work here too.
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. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. ch59 59.4: "The pig louse, HAEMATOPINUS SUIS, is among the largest of all lice and can be observed with the naked eye. H. suis has a worldwide distribution, IS THE ONLY LOUSE INFESTING SWINE, and is an anopluran (sucking) louse... HAEMATOPINUS SUIS IS STRICTLY HOST-SPECIFIC, AND THEIR INTRODUCTION DOES NOT INVOLVE RODENTS, BIRDS, OR ANY OTHER PESTS. THE ENTIRE LIFE CYCLE TAKES PLACE ON THE PIG." No human infestation, dermatitis or bite reaction is described anywhere in the chapter, which does discuss human involvement with the other ectoparasites where there is any -- 59.2.6 records people acting as mechanical vectors of mange mites between herds.
How this level was decided
Level 1. The chapter states strict host specificity twice over -- the only louse of swine, the whole life cycle on the pig, introduction involving no other animal -- and says nothing about people at all, in a chapter that raises human involvement for scabies where it exists. Sucking lice are among the most host-restricted of all arthropod parasites, and nothing in the folder suggests this one is an exception. NOTE THE ONE HUMAN-ADJACENT FACT, which is not a zoonosis and should not be misread as one: lice "have been considered to be VECTORS OF SWINE POX", which is pig-to-pig transmission of another agent, not transmission of anything to a person.
C2 Zoonotic impact
Severity of human illness caused by the agent
No human illness: Agent does not cause illness in people
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. No human illness involving Haematopinus suis is described anywhere in the folder. ch59 59.4: "HAEMATOPINUS SUIS IS STRICTLY HOST-SPECIFIC... THE ENTIRE LIFE CYCLE TAKES PLACE ON THE PIG."
How this level was decided
Level 1, following C1. Under C2 as rescoped, level 1 says pigs are not a source of human illness with this agent, because it does not reach people from pigs.
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. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. ch59 59.4: "THE SPREAD OF LICE IS BY DIRECT CONTACT... LICE ARE OBLIGATE PARASITES AND CANNOT SURVIVE FOR MORE THAN 2-3 DAYS OFF OF THE HOST." On specificity as an exclusion fact: "Haematopinus suis is strictly host-specific, and THEIR INTRODUCTION DOES NOT INVOLVE RODENTS, BIRDS, OR ANY OTHER PESTS." 59.4.2: "CONTROL AND ERADICATION STRATEGIES MENTIONED FOR SCABIES ARE ALSO EFFECTIVE FOR PEDICULOSIS. THIS INCLUDES MULTIPLE TREATMENTS OF SOWS PRIOR TO FARROWING, SEGREGATION OF CLEAN AND UNTREATED ANIMALS, AND TREATMENT OF NEWLY INTRODUCED ANIMALS." The scabies programme those strategies point back to is 59.2.7: "biosecurity measures that focus on careful scrutiny of a minimal number of sources of incoming stock are usually adequate to prevent the introduction of the parasite."
How this level was decided
Level 3, and it is scored the same way as sarcoptes_scabiei in the same chapter for the same reasons, which the chapter itself invites by saying the control and eradication strategies are the same. The route is other pigs, by direct contact, with no reservoir in rodents, birds or the environment and no survival off the host beyond two or three days -- so housing does nothing, and this is not level 2. What excludes it is treating incoming stock and segregating clean animals, which is the routine programme of level 3. NOT LEVEL 1: the chapter treats lice as something a herd can be free of and can be reinfested with, not as something every pig carries.
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, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. ch59 59.4: the pig louse "IS AMONG THE LARGEST OF ALL LICE AND CAN BE OBSERVED WITH THE NAKED EYE... Females are about 6 mm in length... Lice are found on all parts of the body but tend to be focused on the neck, jowls, flanks, and inner surface of the legs. THEY ALSO SEEK SHELTER INSIDE THE EARS, WHERE THEY MAY BE FOUND IN CLUSTERS." 59.4.1: "LICE SHOULD ALWAYS BE CONSIDERED IN THE DIFFERENTIAL DIAGNOSIS OF PRURITUS IN PIGS. INFESTATION CAN BE CONFIRMED BY IDENTIFYING LICE AND/OR NITS. Nits will be cemented to the PROXIMAL (LOWER) PART OF THE HAIR SHAFTS, which helps differentiate them from blow fly eggs, which are more diffuse in distribution. Nits are pearl white when first laid and are 1.5-2 mm in length. Adults have six legs and long sucking mouthparts."
How this level was decided
Level 1, and this is the easiest diagnosis in the register: a 6 mm parasite, visible without magnification, clustered inside the ears of a pig that is rubbing, with an egg that is distinguished from a fly egg by where it is glued to the hair. NO LABORATORY IS INVOLVED AT ALL, which is a step beyond what the level 1 label requires -- it asks for suspicion in normal practice plus confirmation by routine local tests, and here confirmation is looking. Scored level with sarcoptic mange in the same chapter, though the reason differs: mange is level 1 because the pen-side signs and the scraping are routine, and this is level 1 because the parasite can simply be seen.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c5l2, clinical disease is consistent with L2 criteria description"
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. ch59 59.4, and the chapter is unusually candid about the weakness of its own evidence: "THE ECONOMIC IMPORTANCE OF LICE HAS NOT BEEN CRITICALLY EVALUATED TO THE SAME EXTENT AS THAT OF SCABIES. However, it is known that SEVERE PEDICULOSIS RESULTS IN ANEMIA IN YOUNG PIGS and may affect growth rates and feed efficiency. ONE ESTIMATE OF REDUCED GROWTH RATE WAS 50 G/DAY (Hiepe and Ribbeck 1975), ALTHOUGH OTHERS FAILED TO DEMONSTRATE THIS EFFECT. Lice have been considered to be vectors of swine pox, and HIDES FROM PEDICULOTIC SWINE MAY BE UNSUITABLE FOR HIGH-GRADE LEATHER manufacturers." 59.1 gives the general ectoparasite mechanism: reduced growth rate, reduced feed efficiency, loss of carcass value, and trimming or condemnation for skin blemishes.
How this level was decided
INFERRED, AND FLAGGED, because the folder contains a direct contradiction and cannot settle it. THE CONTRADICTION: one study puts the growth cost at 50 g/day, which if real is a large number, and other studies failed to demonstrate any effect at all; the chapter declines to adjudicate and says the economics have never been critically evaluated. LEVEL 2 IS SCORED as the middle reading and on the standing note SCORING/production_cost_impact -- severe pediculosis with anaemia is a real event in young pigs but a sporadic one, lice are uncommon in modern US confinement where bedding is absent and avermectins are given routinely for other reasons, and the leather-grade loss is not a US commercial concern. THE ARGUMENT FOR LEVEL 3 is the 50 g/day figure taken at face value alongside sarcoptic mange at level 3 in the same chapter. THE ARGUMENT FOR LEVEL 1 is that half the literature found no effect. Your view of how much louse infestation US herds actually carry settles this better than the chapter does.
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 market, ancient disease"
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. Haematopinus suis has a worldwide distribution (ch59 59.4) and no trade measure, movement restriction or market response to louse infestation is recorded anywhere in the folder. The only downstream consequence named is that hides from pediculotic swine may be unsuitable for high-grade leather.
How this level was decided
INFERRED. Level 1 under the standing note SCORING/market_impact: a cosmopolitan parasite long present in US pigs with no market move ever observed. THE HIDE POINT IS SCORED IN C5, NOT HERE, and it is worth saying why: it is a downgrade on the individual carcass, paid by the producer, not a disruption to pork or pig markets -- and hides are a byproduct stream of no material weight in US pork economics.
C7 Treatment potential
Potential for treatment to improve outcomes
Little: Effective pathogen-directed treatment is available and works, or animals recover acceptably without it
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. ch59 59.4.2: "The treatment and control of pediculosis is aided by the fact that ALL STAGES OF THE PARASITE OCCUR ON THE PIG. THERAPEUTIC AGENTS MAY BE ADMINISTERED TO THE SWINE IN THE FORM OF SPRAYS, POUR-ONS, OR DUSTS (see Table 59.1). Control can be assisted by sprinkling insecticide granules in the bedding. Pour-ons and dusts have the advantage that they can be used in cold weather... IF THE ACTIVE INGREDIENT IS NOT OVICIDAL, TREATMENT SHOULD BE REPEATED IN 10 DAYS. CONTROL AND ERADICATION STRATEGIES MENTIONED FOR SCABIES ARE ALSO EFFECTIVE FOR PEDICULOSIS." 59.2.5: "THE AVERMECTINS ARE BROAD-SPECTRUM ANTIPARASITICIDES EFFECTIVE AGAINST MOST INTERNAL PARASITES AS WELL AS LICE AND SARCOPTIC MANGE MITES."
How this level was decided
Level 1. Registered products in three formulations are effective, the parasite spends its whole life on the pig so there is nothing to chase in the environment, and the chapter says eradication succeeds. THE LABEL TEST IS SATISFIED: US ivermectin swine labels name Haematopinus suis, and the chapter names the avermectins as effective against lice in terms. The only qualification is that a non-ovicidal product must be repeated at ten days to catch the hatch, which is a dosing instruction rather than an inconsistency of effect -- it does not reach the level 2 clause.
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 imperative for vaccine, disease completely eradicable and excludable without vaccine"
Basis. THE FOLDER HOLDS ONE DOCUMENT, ch59, and the louse is treated in section 59.4 -- about a page. There is no CFSPH factsheet on this entry as there is for the two mange mites. No vaccine against Haematopinus suis is mentioned anywhere in the folder and no vaccine research is referred to. What the chapter offers instead is 59.4.2: therapeutic agents in three formulations, and "control and eradication strategies mentioned for scabies are ALSO EFFECTIVE FOR PEDICULOSIS."
How this level was decided
INFERRED. Level 1 on the "not needed" clause, made as an affirmative claim rather than a default, per your PCV4 rule. The folder supports it: insecticides eradicate the parasite, the whole life cycle is on the pig so there is nowhere for it to hide from treatment, and the disease is a sporadic anaemia of severely infested young pigs. A vaccine against an insect that a pour-on removes is not something the agent's clinical or economic weight justifies. NOTE THAT THIS IS NOT AN ARGUMENT FROM SILENCE about whether vaccination is possible -- anti-arthropod vaccines exist in other species -- it is that this disease does not warrant one.
Levels and evidence are generated from data/assignments/haematopinus_suis.yml; the overview is authored in data/overviews/haematopinus_suis.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.