MYCOPLASMA HYOSYNOVIAE (ARTHRITIS)
LEVELS: Highly unlikely: No controls necessary; Highly unlikely: No evidence of non-foodborne zoonotic transmission; Highly effective: Routine on-farm biosecurity measures are effective in preventing farm-to-farm transmission; Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s); Minor: Low prevalence, typically non-lethal infection with recovery very likely; 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; No availability: Effective vaccines not currently available in the US (or have not been developed); Not feasible: Eradication extremely unlikely
OVERVIEW
Mycoplasma hyosynoviae is a commensal of the tonsils, nasal cavity, and conducting airways that occasionally invades systemically to produce acute non-purulent arthritis in growing and finishing pigs (3-5 months of age). The organism infects only swine and grows rapidly in culture using modified Hayflick's medium. Colonization prevalence is low at weaning but typically peaks between 10-16 weeks of age. Lameness and arthritis develop in only a portion of colonized pigs; the conditions triggering systemic spread are unknown. The main clinical sign is acute lameness affecting one or more joints with soft, fluctuating joint swellings. Involvement of stifle or hock joints can result in a dog-sitting posture. Lameness typically decreases over time until full recovery unless complicated by conditions like osteochondrosis. M. hyosynoviae infections can be a significant welfare issue and contribute to culling and mortality in finishing pigs. No commercial vaccine is available; autogenous vaccines have been used but field trial data is limited. Antimicrobial treatment is the most common control strategy, with efficacy dependent on early initiation.
FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No controls necessary
M. hyosynoviae infects only pigs and is not a foodborne pathogen.
NON-FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No evidence of non-foodborne zoonotic transmission
M. hyosynoviae is strictly host-specific: "infects only swine." No zoonotic transmission has been documented.
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 through direct contact within herds: (1) Tonsillar colonization: "Tonsils are the primary site of colonization...and pigs can become persistent carriers"; (2) Sow-to-piglet transmission: "Sixty percent of sows tested positive for M. hyosynoviae by PCR, while their progeny tested negative at 1–2 days of age, and 13% of the piglets tested positive at 3 weeks of age"; (3) No airborne transmission documented.
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s)
Diagnosis requires laboratory confirmation in affected joints: (1) Clinical suspicion: "M. hyosynoviae should be suspected in cases of acute lameness in fattening pigs older than 10 weeks"; (2) Appropriate sampling critical: "Acutely lame, non-medicated pigs should be selected for sampling, and joints on affected legs should be examined and sampled"; (3) PCR preferred: "has been rapidly replaced by detection with highly accurate PCR-based tests"; (4) Lesions not pathognomonic: "Gross and microscopic lesions in synovial membranes are suggestive of M. hyosynoviae infection, but not pathognomonic, and must be accompanied by confirmation of infection"; (5) Differential diagnosis broad: Must rule out osteochondrosis, nutritional imbalances, genetics, trauma, other infectious causes.
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Minor: Low prevalence, typically non-lethal infection with recovery very likely
Disease affects welfare and productivity: (1) Welfare concern: "infections with M. hyosynoviae can be a significant welfare issue and contribute to the general culling and mortality observed in finishing pigs"; (2) Variable occurrence: Lameness develops in "only a portion of colonized pigs"; (3) Poor body condition: "Pigs have decreased appetite or are reluctant to move, which results in poor body condition."
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: M. hyosynoviae is not a reportable disease; (2) Self-limiting: "Lameness typically decreases with time until there is full recovery."
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 susceptibility documented: "There is a range of sensitivity, with some isolates being overall more resistant while others appear more susceptible."
AMR DEVELOPMENT DRIVEN BY DISEASE MANAGEMENT
Level: Moderate risk: Antibacterial or antiviral treatments are commonly used for treating affected individuals
Antimicrobials are primary control: (1) No commercial vaccine: "No commercial vaccine for the prevention of disease caused by M. hyosynoviae has been developed"; (2) Antimicrobial treatment common: "Antimicrobial treatments are the most common strategy for disease control"; (3) Autogenous vaccines unsuccessful: "an autogenous M. hyosynoviae vaccine could not successfully prevent the development of lameness in finishing pigs."
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 if used early: (1) Susceptible drugs: "M. hyosynoviae isolates have been shown to be sensitive to tetracyclin, tiamulin, valnemulin, linomycin, gentamycin, enrofloxacin, and danofloxacin"; (2) Timing critical: "To be effective, treatment should be initiated early during infection."
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: No availability: Effective vaccines not currently available in the US (or have not been developed)
No effective vaccines: (1) No commercial vaccine: "No commercial vaccine for the prevention of disease caused by M. hyosynoviae has been developed"; (2) Autogenous vaccines ineffective: "In one field trial, an autogenous M. hyosynoviae vaccine could not successfully prevent the development of lameness in finishing pigs."
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Not feasible: Eradication extremely unlikely
Eradication not practical: (1) Persistent carriers: "pigs can become persistent carriers"; (2) High colonization prevalence: Colonization peaks at 10-16 weeks; (3) Commensal organism: Normal inhabitant of tonsils and respiratory tract.