Pasteurella multocida (pneumonic pasteurellosis)

LEVELS: Sometimes occurs; Mild; Already in the herd; Laboratory-dependent; Moderate; Negligible; Some; Available but inconsistent


Register id	`pasteurella_multocida_pneumonia`
Type	bacteria
Scientific name	Pasteurella multocida
NCBI taxid	747
Evidence	1 document(s)
Assigned	2026-09-04, against criteria version `093366e352a2`

Overview

This entry covers pneumonic pasteurellosis only — Pasteurella multocida as a cause of bacterial pneumonia. The same organism's role in progressive atrophic rhinitis is a separate entry. P. multocida is among the commonest and costliest components of the porcine respiratory disease complex, and in the United States pneumonia is the leading cause of death in nursery, grower/finisher and wean-to-finish pigs. It is an opportunist: it colonises the airway poorly unless the lining has already been damaged, so disease effectively requires a prior insult — Mycoplasma hyopneumoniae, PRRSV, influenza, Bordetella or APP. Affected pigs cough, run intermittent fevers, go off feed, grow slowly and in severe cases breathe with difficulty and turn blue; some strains add pleurisy and abscesses. The lesion is a purulent consolidation of the front and lower parts of the lung. Because it is a secondary invader, controlling the primary pathogens is more effective than vaccinating against it, and treatment is difficult because antibiotics penetrate consolidated lung poorly. The organism is also the usual cause of infected animal-bite wounds in people.

C1 Zoonotic potential

Likelihood of transmission from pigs to humans

Sometimes occurs: Known risk of transmission to humans (foodborne or occupational), but requires failure of one or more control points for transmission to humans

Basis. SCOPE OF THE ENTRY: this is PNEUMONIC PASTEURELLOSIS ONLY. Eric, 2026-08-18: "WE NEED TO CONSIDER THIS AS AN AGENT FOR BACTERIAL PNEUMONIA ONLY." Progressive atrophic rhinitis is a separate register entry, already assessed, and ch54 is organised by syndrome so the two do not overlap. Nothing that belongs to PAR is scored here. ch54 54.3: "PASTEURELLA MULTOCIDA IS AN IMPORTANT ZOONOTIC AGENT and is responsible for most human infections related to animal bites or scratches. Dogs and cats are the predominant source, but INFECTION FOLLOWING BITES FROM PIGS, rabbits, rats, and various wild animals HAS BEEN REPORTED... P. multocida is not a usual constituent of the human upper respiratory tract, but STRAINS GENETICALLY IDENTICAL TO THOSE FOUND IN SWINE ARE FREQUENTLY ISOLATED FROM PIG FARMERS AND FROM INHABITANTS OF REGIONS WITH INTENSIVE PIG BREEDING (Donnio et al. 1999; Marois et al. 2009). WATER FROM SCALDING TANKS IS A POTENTIAL SOURCE OF EXPOSURE FOR ABATTOIR WORKERS (Marois et al. 2008)."

How this level was decided

Level 3, and the pig attribution here is stronger than in any entry ruled to level 1 today. This is not human disease with a pig source assumed: strains GENETICALLY IDENTICAL to swine strains are frequently isolated from pig farmers, and the exposure routes named are occupational -- a pig bite, and scalding tank water at the abattoir. Both are control points that can hold or fail, which is the level 3 label. NOT LEVEL 4: nothing here happens through intact controls, and no respiratory protection or vector control is in play; a bite and a scald tank are avoidable.

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

How this level was decided

Level 2. The usual outcome is a local skin or soft tissue infection, and the chapter says the serious forms are generally confined to immunocompromised patients -- mild and usually self-limiting, with serious disease only rarely, which is the level 2 label. The pig farmers carrying swine strains are described as healthy carriers rather than patients.

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. SCOPE OF THE ENTRY: this is PNEUMONIC PASTEURELLOSIS ONLY. Eric, 2026-08-18: "WE NEED TO CONSIDER THIS AS AN AGENT FOR BACTERIAL PNEUMONIA ONLY." Progressive atrophic rhinitis is a separate register entry, already assessed, and ch54 is organised by syndrome so the two do not overlap. Nothing that belongs to PAR is scored here. ch54 54.8.2: "Isolation of the organism from the lung or upper airways can similarly not be used as the only criteria for establishing a diagnosis, as P. MULTOCIDA CAN BE DETECTED BY PCR OR ISOLATED FROM CLINICALLY NORMAL PIGS." 54.5.3: "Prior infection with only B. bronchiseptica results in COLONIZATION OF THE NASAL CAVITY AND TONSIL WITHOUT OVERT DISEASE, and this could be a means by which HEALTHY CARRIER PIGS ARISE UNDETECTED. LONG-TERM CARRIAGE OF NONTOXIGENIC STRAINS IN THE TONSIL may lead to pneumonia in the face of other predisposing factors that arise at a later time." 54.1: "P. multocida is AMONG THE BACTERIAL AGENTS MOST FREQUENTLY ISOLATED FROM PNEUMONIC LUNGS with a particularly high prevalence in finishing pigs", and "NONTOXIGENIC STRAINS CONTINUE TO COMPRISE THE MAJORITY OF LUNG ISOLATES" (54.5.3).

How this level was decided

Level 1. The strains that cause pneumonic pasteurellosis are non-toxigenic tonsillar commensals of clinically normal pigs, so there is no introduction event to prevent. THIS IS CONSISTENT WITH, NOT CONTRARY TO, YOUR PAR RULING, and the two entries are worth reading together: you put progressive atrophic rhinitis at C3 level 3 with the reason "B.bord is probably not excludable from herds BUT TOXIGENIC P.MULT IS EXCLUDABLE... The disease/P.mult agent CAN BE TESTED FOR AND EXCLUDED FROM A FARM." That is true of the TOXIGENIC strains PAR depends on. It is not true of the organism as a whole, which every pig carries, and the pneumonia entry is scored on the strains that actually cause it.

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. SCOPE OF THE ENTRY: this is PNEUMONIC PASTEURELLOSIS ONLY. Eric, 2026-08-18: "WE NEED TO CONSIDER THIS AS AN AGENT FOR BACTERIAL PNEUMONIA ONLY." Progressive atrophic rhinitis is a separate register entry, already assessed, and ch54 is organised by syndrome so the two do not overlap. Nothing that belongs to PAR is scored here. ch54 54.8.2: "LUNG LESIONS CAUSED BY P. MULTOCIDA ARE NOT PATHOGNOMONIC and cannot be used as the only criteria to establish a definitive diagnosis. ISOLATION OF THE ORGANISM FROM THE LUNG OR UPPER AIRWAYS CAN SIMILARLY NOT BE USED AS THE ONLY CRITERIA... The history of the outbreak, HISTOPATHOLOGY, AND ISOLATION of the organism should be used to confirm the original presumptive diagnosis... THERE IS NO SEROLOGIC TEST ROUTINELY AVAILABLE to assist in the diagnosis of P. multocida lung infection. Differential diagnosis should include other causes of purulent bronchopneumonia or pleuropneumonia, such as B. bronchiseptica, M. hyopneumoniae, Streptococcus suis, Glaesserella parasuis, Trueperella pyogenes, Salmonella Choleraesuis, A. suis, and A. pleuropneumoniae. ACCURATE CLINICAL DIFFERENTIATION IS OFTEN DIFFICULT... As P. MULTOCIDA IS RARELY A PRIMARY AGENT, deeper investigation for underlying agents or factors that predispose pigs to secondary infection should be considered."

How this level was decided

Level 2. Culture and identification are ordinary bacteriology at any regional laboratory, so a validated method plainly exists -- but nothing about the presentation points here, the differential runs to eight agents, and there is no serology. That is the level 2 label. NOTE WHAT MAKES THIS HARDER THAN A TYPICAL LEVEL 2 WITHOUT MOVING IT: the difficulty is not finding the organism, it is deciding whether finding it means anything, because the same organism is cultured from normal lungs and is rarely the primary agent. The chapter's answer -- history plus histopathology plus isolation, then look for what let it in -- is a diagnostic judgment rather than a test result.

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

How this level was decided

Level 3. The chapter gives a US-specific statement of exactly the kind the standing note SCORING/production_cost_impact asks for -- pneumonia is the leading cause of death in US growing pigs, and this organism is among the most common and costliest components of it, cited to USDA 2015. The loss is mortality, lengthened time to market, culls, reduced gain and treatment cost, continuously, which is the level 3 label including its endemic clause. NOT LEVEL 4: this is the background cost of growing pigs in the US rather than a threat to the viability of a unit, and the industry absorbs it. NOTE THE ATTRIBUTION PROBLEM AND WHY IT DOES NOT LOWER THE LEVEL: P. multocida is rarely the primary agent, so some of this cost is shared with M. hyopneumoniae, PRRSV and influenza. The chapter nonetheless names it among the costliest components, and C5 asks what the infected farm loses when this agent is in the mix.

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, no impact on markets"

How this level was decided

INFERRED. Level 1 under the standing note SCORING/market_impact: an agent universally present and routinely diagnosed in US pigs with no market move ever observed. The zoonotic dimension is occupational rather than foodborne and does not reach a consumer.

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. SCOPE OF THE ENTRY: this is PNEUMONIC PASTEURELLOSIS ONLY. Eric, 2026-08-18: "WE NEED TO CONSIDER THIS AS AN AGENT FOR BACTERIAL PNEUMONIA ONLY." Progressive atrophic rhinitis is a separate register entry, already assessed, and ch54 is organised by syndrome so the two do not overlap. Nothing that belongs to PAR is scored here. ch54 54.10.2: "TREATMENT OF PULMONARY P. MULTOCIDA INFECTIONS WITH ANTIBIOTICS IS CHALLENGING BECAUSE OF THE DIFFICULTY OF ACHIEVING THERAPEUTIC CONCENTRATIONS IN CONSOLIDATED, PNEUMONIC LUNGS. PARENTERAL ANTIBIOTICS ARE PREFERABLE, INCLUDING AMPICILLIN, CEFTIOFUR, ENROFLOXACIN, AND TULATHROMYCIN. In-feed antibiotics, such as chlortetracycline and tilmicosin, are best used on a preventative basis." On resistance: "P. MULTOCIDA HAS HISTORICALLY BEEN STABLE IN ITS RESISTANCE PATTERN IN NORTH AMERICA, WITH RATHER LOW RESISTANCE to ampicillin, ceftiofur, enrofloxacin, florfenicol, gentamicin, penicillin, spectinomycin, and tulathromycin and moderate for oxytetracycline and tetracycline (Hayer et al. 2020)."

How this level was decided

Level 2, and the reason is delivery rather than susceptibility, which is unusual enough to state plainly. THE LABEL TEST GIVES LEVEL 1: US swine respiratory labels for ceftiofur and tulathromycin name Pasteurella multocida explicitly, and North American resistance is low and stable. LEVEL 2 IS SCORED ANYWAY, on the same reasoning that holds Actinobacillus pleuropneumoniae there -- your 2026-09-02 rule makes the label the first test, not the only one, and the level 2 clause "works only in some circumstances" is satisfied by the chapter's own opening sentence: the drug cannot reach therapeutic concentration in a consolidated lung. The organism is susceptible in the tube and the pig still has the pneumonia.

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

CONFIRMED by Eric. The assignment reached this level from the evidence, and he has reviewed and ratified it.

Confirmed by Eric. CONFIRMED. "c8l2, textbook example of vaccines being available but with questionable or unpredicatble efficacy"

Basis. SCOPE OF THE ENTRY: this is PNEUMONIC PASTEURELLOSIS ONLY. Eric, 2026-08-18: "WE NEED TO CONSIDER THIS AS AN AGENT FOR BACTERIAL PNEUMONIA ONLY." Progressive atrophic rhinitis is a separate register entry, already assessed, and ch54 is organised by syndrome so the two do not overlap. Nothing that belongs to PAR is scored here. ch54 54.10.2: "UNDER FIELD CONDITIONS, THE EFFECTIVENESS OF VACCINATION AGAINST PNEUMONIA WITH P. MULTOCIDA IS DUBIOUS. A recent analysis of trends and advances in P. multocida vaccination indicated that THIS IS UNLIKELY TO CHANGE IN THE NEAR FUTURE." 54.9.2: "Identification of immunogens or immune responses important for protection against pneumonic pasteurellosis in swine HAS BEEN ELUSIVE... THE ABSENCE OF A RELIABLE PULMONARY DISEASE MODEL IN PIGS MAKES VACCINE EFFICACY DIFFICULT TO ASSESS... OVERALL, THE EFFECTIVENESS OF VACCINES IN CONTROLLING PNEUMONIC PASTEURELLOSIS IN SWINE IS QUESTIONABLE." What is recommended instead: "control of the primary pathogens such as M. hyopneumoniae, IAV, or PRRSV through vaccination, medication, or management practices may be THE MOST EFFICIENT METHOD OF CONTROLLING THE DISEASE." P. multocida bacterins and toxoids exist and are sold, largely for PAR (ch44 44.10).

How this level was decided

Level 2, AND FLAGGED, because this is the level 2 / level 3 boundary and the chapter's language is stronger than "inconsistent". LEVEL 2 IS SCORED: P. multocida bacterins are commercially available in the US and are given, so a product exists, which is what level 3 denies. THE ARGUMENT FOR LEVEL 3 IS SERIOUS: the chapter says field effectiveness against PNEUMONIA is dubious and questionable and unlikely to improve, which is close to saying no EFFECTIVE vaccine is available -- and the disease plainly warrants one, since pneumonia is the leading cause of death in US growing pigs. On that reading this is a genuine gap and belongs at level 3. WHAT I HAVE WEIGHED AGAINST IT: the chapter also says the efficient route is vaccinating against the PRIMARY pathogens instead, which is a statement that the gap is filled from another direction rather than left open, and PRRSV sits at level 2 on comparable "variably effective" language. Your call.

Levels and evidence are generated from data/assignments/pasteurella_multocida_pneumonia.yml; the overview is authored in data/overviews/pasteurella_multocida_pneumonia.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.

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