PASTEURELLA MULTOCIDA - PROGRESSIVE ATROPHIC RHINITIS (PAR)
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); Moderate: Manageable losses related to endemic (population) or chronic (individual) occurrence; 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; Moderate risk: Antibacterial or antiviral treatments are commonly used for treating affected individuals; Available but with uncertain efficacy: Limited treatments available in US or are only effective in some situations; Available but uncertain efficacy: Commercial or autogenous vaccines exist in the US but protection may be inconsistent; Possible: Eradication possible but likely to require major changes into logistic systems, regulatory environment, infrastructure, and producer behaviors
OVERVIEW
Progressive atrophic rhinitis (PAR) is a severe, often irreversible form of atrophic rhinitis caused by toxigenic strains of Pasteurella multocida, either alone or in combination with Bordetella bronchiseptica. The disease is characterized by stunted development or total disappearance of the nasal turbinates, snout deformation, and reduced growth performance. The essential virulence factor is P. multocida toxin (PMT), a 146 kDa protein that interferes with normal bone remodeling and formation. Most PAR isolates are capsular serotype D, though type A may also be involved. B. bronchiseptica infection is the common predisposing factor, causing mucosal damage that facilitates P. multocida colonization. Pigs infected within the first few weeks of life are most severely affected. Clinical signs include sneezing, nasal discharge, epistaxis, brachygnathia superior (shortened upper jaw giving upturned nose appearance), and lateral snout deviation. More severe disease is associated with intensive indoor production, high stocking density, poor hygiene, poor ventilation, and exposure to dust and ammonia. Control combines sow vaccination (PMT toxoid-containing vaccines are superior), antimicrobial treatment, and management improvements. Infection can be eradicated by depopulation and restocking with clean breeding stock.
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) Bite-related infections: "Pasteurella multocida is an important zoonotic agent and is responsible for most human infections related to animal bites or scratches"; (2) Pig-related transmission: "infection following bites from pigs...has been reported"; (3) Occupational carriage: "strains genetically identical to those found in swine are frequently isolated from pig farmers and from inhabitants of regions with intensive pig breeding"; (4) Abattoir exposure: "Water from scalding tanks is a potential source of exposure for abattoir workers"; (5) Clinical disease: "Most human carriers remain healthy, but P. multocida may also be associated with acute or chronic respiratory disease."
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 is primarily through 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) Aerosols limited: "the bacterium may occasionally be spread via aerosols" but this is not the primary route; (4) Environmental survival limited: "P. multocida survives for approximately 1 week at 4°C"; (5) Susceptible to disinfection: "Several disinfectants suitable for farm use are bactericidal."
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Easy: Distinct clinical signs and/or existing test(s) available at local/regional laboratory(s)
Clinical signs and laboratory confirmation are available: (1) Pathognomonic signs: "Animals showing lateral deviation of the snout or marked brachygnathia superior almost always have pronounced turbinate atrophy"; (2) Slaughter examination: "The prevalence and severity of turbinate atrophy are best estimated by examination of nasal turbinates during regular slaughter checks"; (3) Culture available: "P. multocida grows readily on blood agar"; selective media available; (4) PCR for toxin: "PCR is now frequently used for PMT detection"; (5) MALDI-TOF identification: Differentiates types A and D simultaneously with speciation.
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Moderate: Manageable losses related to endemic (population) or chronic (individual) occurrence
Economic impact is variable: (1) Growth effects: "PAR may negatively affect the growth rate and the efficiency of feed conversion"; (2) Outbreak severity varies: "moderate to severe outbreaks may have a substantial economic impact"; (3) Endemic herds: "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"; (4) Feed intake reduced: "Feed consumption may be influenced by PAR, since piglets with acute rhinitis may accept feed less readily."
EFFECT ON DOMESTIC OR EXPORT MARKETS
Level: Negligible: Little or no market disruption when disease occurs on one or more farms
No significant trade implications: (1) Not regulated: PAR is not a reportable or trade-restricted disease; (2) Endemic worldwide: Present in swine populations globally; (3) Production disease: Impact is on farm economics, not trade.
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
Increasing resistance documented: (1) Sulfonamide resistance: "Increasing resistance to some sulfonamides has been reported for both B. bronchiseptica and P. multocida"; (2) Tetracycline resistance: "an increase in resistance of P. multocida to oxytetracycline"; (3) Geographic variation: "much higher and less stable levels of resistance reported from other continents"; (4) Susceptibility testing recommended: "determining the antibiotic susceptibility profile for isolates from a particular herd is prudent."
AMR DEVELOPMENT DRIVEN BY DISEASE MANAGEMENT
Level: Moderate risk: Antibacterial or antiviral treatments are commonly used for treating affected individuals
Antimicrobials commonly used: (1) Sow feed medication: "To reduce vertical transmission from infected dams to suckling offspring, the sow's feed can be medicated during the final month of gestation"; (2) Piglet injections: "Suckling piglets are best medicated by strategic injections of antibacterial agents in therapeutic doses through the first 3–4 weeks of life"; (3) Growing pig medication: "PAR in weaned pigs...can be controlled to some extent by medication of rations or drinking water."
AVAILABILITY OF EFFECTIVE TREATMENT OPTIONS
Level: Available but with uncertain efficacy: Limited treatments available in US or are only effective in some situations
Multiple antimicrobials effective: (1) Injectable options: "Drugs used commonly for the treatment of P. multocida are ampicillin, ceftiofur, enrofloxacin, and tulathromycin"; (2) Feed/water medication: "tetracyclines, tilmicosin, and trimethoprim/sulfa"; (3) B. bronchiseptica consideration: "because of resistance, ampicillin and ceftiofur should not be the first choice if B. bronchiseptica is a factor."
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: Available but uncertain efficacy: Commercial or autogenous vaccines exist in the US but protection may be inconsistent
Vaccines effective with PMT toxoid: (1) Sow vaccination effective: "Sow vaccination induces a significant degree of passive colostral protection against PAR"; (2) PMT toxoid essential: "PMT is an important component of vaccines for PAR, and those with added PMT toxoid offer superior protection"; (3) Bacterins less effective: "Bacterins made from toxigenic strains...vary in efficacy since they often fail to induce adequate toxin-specific antibodies"; (4) Not sterilizing: "Vaccination does not provide sterilizing immunity but will reduce the pathogen load and significantly diminish or abolish clinical disease."
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Possible: Eradication possible but likely to require major changes into logistic systems, regulatory environment, infrastructure, and producer behaviors
Eradication is achievable: (1) Depopulation effective: "Infection can be eradicated by depopulation and restocking"; (2) Clean herds maintainable: "clean herds may be maintained free from PAR by isolation, herd monitoring, and the use of clean breeding stock"; (3) Tonsil reservoir: The tonsil serves as reservoir making elimination without depopulation difficult.