Tetanus
LEVELS: Highly unlikely; Severe; Housing alone keeps it out; Routine; Negligible; Negligible; Some; Available, or not needed
| Register id | clostridium_tetani |
| Type | bacteria |
| Scientific name | Clostridium tetani |
| NCBI taxid | 1513 |
| Evidence | 1 document(s) |
| Assigned | 2026-09-04, against criteria version 093366e352a2 |
Overview
Clostridium tetani causes tetanus. Its spores are permanent residents of soil and cannot be eliminated from the environment; disease follows when they germinate in a wound where oxygen is scarce. In pigs that almost always means a procedure — castration, tail docking, an infected navel — so most cases are in young animals, though sows can be affected through a contaminated prolapse. The organism stays at the wound but its toxin travels up the nerves to the spinal cord, where it blocks the signals that let muscles relax, producing sustained contraction. An affected pig stiffens, walks rigidly, holds its ears erect and its tail out, and finally lies on its side arched backwards; spasms are set off by noise or touch and can be violent enough to break bones. Death comes from paralysis of the muscles of breathing, and once signs appear the outlook is poor. Prevention — clean wound management and toxoid vaccination — is the whole of the answer.
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. ch47 47.4, opening the neurotoxigenic section: "Neurotoxic clostridial diseases include tetanus caused by C. tetani and botulism caused by C. botulinum. Neither disease is zoonotic; hence, there is no public health concern."
How this level was decided
Level 1, stated outright. Human tetanus is common enough worldwide, but it comes from the same ubiquitous soil spores rather than from pigs -- there is no transmission from pigs to people, which is what C1 measures.
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
CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.
Confirmed by Eric. CONFIRMED. "c2l4, severe disease in people". This settles the evidence limitation the pass flagged: ch47 47.4 says only "Neither disease is zoonotic; hence, there is no public health concern" and stops, because the folder is a swine reference and was never assembled to describe human tetanus, so the level rested on general medical knowledge rather than on anything in the folder. His ruling supplies it. C1 records separately, at level 1, that pigs are not where anyone gets tetanus -- which is the whole point of the 2026-09-04 split between exposure and consequence.
Basis. ch47 47.4: "Neither disease is zoonotic; hence, there is no public health concern."
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. Tetanus is a life-threatening spastic paralysis with substantial mortality even when treated. EVIDENCE LIMITATION, and it applies to this whole group: ch47 47.4 says only "Neither disease is zoonotic; hence, there is no public health concern" and stops, because the folder is a swine reference and was never assembled to describe human tetanus. The level rests on general medical knowledge, not on the folder.
PREVIOUS ANSWER, written under the pig-attribution reading: Level 1. C2 scores level 1 where the agent does not cause disease in people BY TRANSMISSION FROM PIGS, which follows from the C1 reading above. NOTE FOR THE REPORT: this level 1 must not be read as "tetanus is harmless to people" -- it records that pigs are not a source.
C3 Herd introduction risk
Effort required to keep the agent out of the herd
Housing alone keeps it out: Raising pigs indoors and off soil breaks the cycle, so no ongoing biosecurity program is needed and only outdoor herds stay exposed
Corrected by Eric from L1 Already in the herd. Reason: MOVED L1 -> L2, overturning the pass on 2026-09-03. His words: "L2, i don't care what the literature says about carrier pigs, this is insignificant. main route of entry without any question is soil exposure." THE PASS HAD JUST MOVED THIS CELL TO LEVEL 1 the same day, on the chapter's line that control is preventing wound contamination "by soil OR FECES" -- reading the faecal half as meaning the organism is already in the barn. He rejects that reading outright and it is his second rejection of the carrier-pig argument in the same sheet. Soil is the route, housing closes it, level 2.
Basis. ch47 47.4.1.1: "It forms terminal spores that are ubiquitous in the environment. Spores often enter via traumatic wounds, including, but not limited to, those from tail docking and castration." 47.4.1.5: "There is no practical way to eliminate spores from soil, so control is directed toward prevention of wound contamination by soil or feces." 47.4.1.2: "Spores may remain latent in healed wounds for 10 years or more."
How this level was decided
MOVED L5 -> L1 on 2026-09-03, when C3 was reduced to four levels and the whole level 5 block was re-read against the exclusion test rather than the reservoir test. Eric: "C3 is about exclusion, not reservoirs per se, though the two are related", and "who cares about reservoirs? Reservoirs really don't matter as long as you keep domestic pigs from becoming infected through biosecurity implementation." THE PREVIOUS LEVEL WAS NEVER JUDGED: this entry carried a RENUMBERED L4 -> L5 stamp from 2026-09-01, meaning it was moved past the newly created housing level rather than assessed against it. the chapter says control is preventing wound contamination "by soil OR FECES", and the wounds are tail docking and castration -- faeces are in the barn, so housing does not close this, and spores travel with the pigs. Level 1: there is no introduction event to prevent.
EARLIER REASONING, kept because it is the evidence read: Level 5, and the chapter states the level 5 test in one sentence: there is no practical way to eliminate spores from soil. The reservoir is the environment itself, it sits entirely outside the farm and the industry, and nobody can remove it. Note what this does NOT mean -- the level is not about spores reaching the pig despite confinement, it is about permanence, and the honest reading of the chapter is that control is directed at the wound rather than at the agent because the agent cannot be got rid of.
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. ch47 47.4.1.4: "Diagnosis is based on typical clinical signs. An obvious area of infection (e.g. a castration wound or umbilical abscess) may be apparent." "The organism may be isolated by bacteriologic culture or identified by immunofluorescence from suspect wounds, but this is usually not necessary if there is adequate antemortem clinical observation of the affected animals." 47.4.1.3: erect ears, straight extended tail, protruding nictitating membrane, lateral recumbency in opisthotonus with all four legs extended posteriorly.
How this level was decided
Level 1, and one of the cleanest in the register. The presentation is unmistakable and pathognomonic in a way almost nothing else in swine medicine is, and the chapter says confirmation is usually not even necessary. When it is wanted, culture and immunofluorescence are routine regional laboratory work.
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, in general has negligible cost on production. The unique presentation are poorly managed outdoor farrowing herds in which case it is basically a lethal infection when a neonate develops the disease. The US never sees this in confinement farrowing. So I think I would also classify it as C3L2 (differetn from what you scored) because although no question it is soil borne, it is exquisitly excludable by moving indoors. Somewhat like A.suum - essentiually any bit of dirt in the world that has ever had a pig near it in the last 50 years probably has roundworm eggs in it so it is also sort of soil borne but we know moving pigs indoors will resolve the issue. Housing trumps environment in these cases."
Basis. ch47 47.4.1: "Swine of all ages may be affected, but most cases involve young pigs and originate with castration or tail docking wounds and umbilical infection." The chapter gives no incidence, no case count and no mortality figure for swine tetanus, and describes control entirely in terms of sanitary technique.
How this level was decided
INFERRED. The chapter records the disease without ever suggesting it is common, and describes it throughout as an individual-animal event following a specific wound. Under the standing note SCORING/production_cost_impact this is scored on modern US production, where sanitary castration, prompt navel treatment and clean farrowing accommodation are standard and clinical tetanus in pigs is a rarity. No measurable effect on cost of production. Level 1. FLAGGED as inferred from the absence of any figure rather than from a stated one, and level 2 is defensible if Eric knows of herds where it recurs.
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, old disease with no evidence to suggest diagnosis would impact markets"
Basis. Section 47.4.1 records no trade measure, movement control or consumer response, and the chapter states that tetanus is not zoonotic.
How this level was decided
INFERRED. A non-zoonotic, sporadic, individual-animal disease arising from wound contamination has no route to pork supply or demand. 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. ch47 47.4.1.5: "With even moderate clinical tetanus, prognosis is poor, and there is little evidence that treatment is of real benefit. Various suggested treatments include reopening castration wounds and flushing them with hydrogen peroxide, administration of antitoxin to neutralize toxins not already fixed by nervous tissue, administration of antibiotics, and the use of tranquilizers or barbiturates as muscle relaxants." "Prophylactic use of large doses of long-acting penicillin or tetracyclines may be superior to antitoxin in preventing experimental tetanus if treatment is instituted within a few hours after infection."
How this level was decided
Level 2. Treatment exists and there is a great deal of it, but the chapter says the prognosis is poor once signs are moderate and that there is little evidence any of it helps -- the toxin is already fixed to nervous tissue. What does work is intervention within hours of the wound, before there is anything to treat. Treatment that works only in some circumstances is level 2 exactly. It is not level 3, because the outcome is reliably improved by prophylaxis and by toxoid rather than left unaddressed.
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. ch47 47.4.1.5: "Active immunity may be obtained from a single injection of alum-precipitated tetanus toxoid, and excellent protection for 1 year or more can be expected if three doses are given several weeks apart." "Passive immunization with tetanus antitoxin, prophylactic use of antibiotics, active immunization with tetanus toxoid, or a combination of these methods may be indicated."
How this level was decided
Level 1, and it reads the same on both clauses of the reworded criterion. Tetanus toxoid is one of the oldest and most reliable vaccines in veterinary medicine and is freely available in the US, so it is available and it works. It is also not routinely given to pigs, because the disease is rare enough that sanitary technique is the whole programme -- so the disease does not economically justify vaccinating either. Level 1 whichever way it is read.
Levels and evidence are generated from data/assignments/clostridium_tetani.yml; the overview is authored in data/overviews/clostridium_tetani.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.