PASTEURELLA MULTOCIDA - PNEUMONIC PASTEURELLOSIS
LEVELS: Highly unlikely: No controls necessary; Occupational exposure risk: Non-foodborne transmission pathway(s) that are strongly associated with occupational exposure and can lead to human infection; Highly effective: Routine on-farm biosecurity measures are effective in preventing farm-to-farm transmission; Easy: Distinct clinical signs and/or existing test(s) available at local/regional laboratory(s); Substantial: Unsustainable acute or chronic losses related to severe clinical signs in a high prevalence of animals; Negligible: Little or no market disruption when disease occurs on one or more farms; High risk: Resistance to antibacterial or antiviral treatments is, or can be expected to be a common problem; High risk: Antibacterial or antiviral treatments commonly used on affected groups, or for prophylaxis; Available but with uncertain efficacy: Limited treatments available in US or are only effective in some situations; No availability: Effective vaccines not currently available in the US (or have not been developed); Not feasible: Eradication extremely unlikely
OVERVIEW
Pneumonic pasteurellosis is a purulent bronchopneumonia caused by opportunistic Pasteurella multocida infection following primary infections by predisposing bacterial and viral pathogens. P. multocida is among the most common and costly components of the porcine respiratory disease complex (PRDC), with particularly high prevalence in finishing pigs. Most pneumonic isolates are capsular serotype A, though type D may be increasing. The organism poorly colonizes the respiratory tract in the absence of preexisting mucosal damage; coinfection with M. hyopneumoniae, PRRSV, B. bronchiseptica, A. pleuropneumoniae, or other primary pathogens is essential for disease development. Clinical signs include coughing, intermittent fever, depression, anorexia, reduced growth rate, labored breathing, and in severe cases cyanosis. Some strains produce pleuritis and abscessation with more severe disease. Lesions consist of cranioventral consolidation with purulent exudate in airways. Treatment with antibiotics is challenging due to difficulty achieving therapeutic concentrations in consolidated lungs; parenteral administration is preferred. Vaccination effectiveness against pneumonic pasteurellosis is questionable; control of primary pathogens (M. hyopneumoniae, IAV, PRRSV) is more efficient.
FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No controls necessary
P. multocida is not transmitted through food consumption. Human infections are associated with animal bites or scratches, not foodborne transmission.
NON-FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Occupational exposure risk: Non-foodborne transmission pathway(s) that are strongly associated with occupational exposure and can lead to human infection
P. multocida is a zoonotic pathogen: (1) Occupational carriage: "strains genetically identical to those found in swine are frequently isolated from pig farmers"; (2) Respiratory disease possible: "P. multocida may also be associated with acute or chronic respiratory disease"; (3) Immunocompromised at risk: "Appropriate precautions should be observed by immunocompromised persons who have contact with swine infected with P. multocida."
EFFECTIVENESS OF ON-FARM BIOSECURITY IN PREVENTING FARM-TO-FARM TRANSMISSION
Level: Highly effective: Routine on-farm biosecurity measures are effective in preventing farm-to-farm transmission
Transmission requires direct contact: (1) Nose-to-nose transmission: "nose-to-nose contact is the most common route of infection"; (2) Introduction via pigs: "The introduction of P. multocida into a herd is usually by the introduction of infected swine"; (3) Vertical and horizontal spread: "Spread within a herd occurs rapidly both vertically from infected dam to suckling piglets and horizontally between infected and uninfected animals."
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Easy: Distinct clinical signs and/or existing test(s) available at local/regional laboratory(s)
Diagnosis relies on clinical signs, histopathology, and culture: (1) PRDC presentation: Clinical signs typical of respiratory disease complex; (2) Culture readily available: "Optimal specimens include swabs of tracheobronchial exudate and affected lung tissue"; (3) MALDI-TOF identification: "MALDI-TOF mass spectrometry has largely replaced routine biochemical bacterial identification"; (4) PCR available: Though culture is commonly used due to ease; (5) Commensal consideration: "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."
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Substantial: Unsustainable acute or chronic losses related to severe clinical signs in a high prevalence of animals
Major economic impact as PRDC component: (1) Leading cause of death: "In the United States, pneumonia is the leading cause of death in nursery, grower/finisher, and wean-to-finish pigs"; (2) Common isolate: "P. multocida is among the most common and costly components of the porcine respiratory disease complex"; (3) Performance losses: "Reduced weight gain and the cost of treating sick animals further the economic impact"; (4) High prevalence in finishers: "P. multocida is among the bacterial agents most frequently isolated from pneumonic lungs with a particularly high prevalence in finishing pigs."
EFFECT ON DOMESTIC OR EXPORT MARKETS
Level: Negligible: Little or no market disruption when disease occurs on one or more farms
No trade implications: (1) Not regulated: Pneumonic pasteurellosis is not reportable; (2) Endemic worldwide: Common component of respiratory disease globally.
PATHOGEN'S ABILITY TO DEVELOP AND SPREAD RESISTANCE
Level: High risk: Resistance to antibacterial or antiviral treatments is, or can be expected to be a common problem
Variable resistance patterns: (1) North American stability: "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"; (2) Geographic variation: "much higher and less stable levels of resistance reported from other continents"; (3) Monitoring critical: "Continued monitoring of resistance patterns as well as following guidelines for antimicrobial use is critical."
AMR DEVELOPMENT DRIVEN BY DISEASE MANAGEMENT
Level: High risk: Antibacterial or antiviral treatments commonly used on affected groups, or for prophylaxis
Antimicrobials widely used for PRDC: (1) Treatment challenges: "Treatment of pulmonary P. multocida infections with antibiotics is challenging because of the difficulty of achieving therapeutic concentrations in consolidated, pneumonic lungs"; (2) Parenteral preferred: "Parenteral antibiotics are preferable"; (3) Preventive use: "In-feed antibiotics, such as chlortetracycline and tilmicosin, are best used on a preventative basis"; (4) PRDC management: Antimicrobials commonly used for respiratory disease complex management.
AVAILABILITY OF EFFECTIVE TREATMENT OPTIONS
Level: Available but with uncertain efficacy: Limited treatments available in US or are only effective in some situations
Multiple options but with limitations: (1) Parenteral antibiotics: "ampicillin, ceftiofur, enrofloxacin, and tulathromycin"; (2) Feed medication: "chlortetracycline and tilmicosin"; (3) Penetration challenge: Difficulty achieving therapeutic levels in consolidated lungs limits effectiveness.
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: No availability: Effective vaccines not currently available in the US (or have not been developed)
Vaccines have questionable efficacy: (1) Dubious effectiveness: "Under field conditions, the effectiveness of vaccination against pneumonia with P. multocida is dubious"; (2) Future outlook poor: "A recent analysis of trends and advances in P. multocida vaccination indicated that this is unlikely to change in the near future"; (3) Primary pathogen control preferred: "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."
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Not feasible: Eradication extremely unlikely
Eradication not feasible: (1) Commensal organism: "In many herds, the organism is detectable in the nose and tonsils of healthy animals and may persist for months or even years with little evidence of disease"; (2) Tonsil reservoir: "The tonsil, particularly the tonsillar crypt, appears to be the preferred habitat of P. multocida in swine"; (3) Secondary pathogen: Requires control of multiple primary pathogens; (4) Ubiquitous: Present in swine populations worldwide.