MYCOPLASMA HYORHINIS (POLYSEROSITIS AND 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 hyorhinis is a commensal bacterium of swine that causes polyserositis and polyarthritis primarily in nursery-age pigs (3-10 weeks). While colonization of the tonsils and respiratory epithelium is nearly universal by the end of the nursery period, systemic disease develops in only a portion of infected pigs. The organism has remarkable membrane lipoprotein diversity through variable protein expression and size, thought to be important for pathogenesis and immune evasion. M. hyorhinis has been associated with eustachitis, otitis, conjunctivitis, abortions, pneumonia, and recently fibrinopurulent meningitis with central nervous system inflammation. The organism is recognized as an emerging pathogen in North America, whether due to true increased prevalence or improved diagnostics. M. hyorhinis persists in herds even after elimination efforts including herd closure and antibiotic treatment. No commercial vaccines are available; autogenous vaccines are used in some production systems but efficacy data is limited. Control relies primarily on antimicrobial therapy, with decreased susceptibility or resistance documented to certain drugs.
FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No controls necessary
M. hyorhinis is not a foodborne pathogen. While "Several studies have reported an association between the presence of M. hyorhinis and a variety of human carcinomas," "the causality of M. hyorhinis in human disease has not been established."
NON-FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No evidence of non-foodborne zoonotic transmission
M. hyorhinis does not cause established human disease: (1) No confirmed zoonosis: "the causality of M. hyorhinis in human disease has not been established"; (2) Farm worker study negative: "A study looking into the detection of M. hyorhinis in nasal swabs obtained from swine farmers failed to show a high prevalence of the bacterium in that population."
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: (1) Nasal secretion transmission: "Like most other Mycoplasma spp. affecting swine, M. hyorhinis is thought to be transmitted in nasal secretions by direct contact among pen mates and in the farrowing house from colonized dams to piglets"; (2) No airborne transmission documented: Unlike M. hyopneumoniae; (3) High colonization prevalence: "almost 100% detection at the group level has been reported at the end of the nursery period" but this represents commensal colonization, not necessarily disease.
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Moderate: Clinical signs not unique but existing tests available at local/regional laboratory(s)
Diagnosis requires confirmation in lesion sites: (1) Commensal status complicates diagnosis: "Because M. hyorhinis is a commensal in the tonsil, nasal cavity, and lungs, bacterial detection in any of these sites does not confirm it as the cause of disease in systemic sites"; (2) PCR and culture available: "Diagnosis of M. hyorhinis is typically performed by culture or PCR"; (3) Appropriate samples critical: "Appropriate samples for confirmation of infection include fibrin or swabs collected from serosal surfaces or joints with lesions"; (4) Rule out other causes: Must confirm characteristic lesions and eliminate other causal agents (G. parasuis, S. suis, A. suis).
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Minor: Low prevalence, typically non-lethal infection with recovery very likely
Disease is sporadic with variable severity: (1) Emerging pathogen: "M. hyorhinis is recognized as an emerging pathogen in North America and other regions"; (2) Most colonized pigs unaffected: "Most colonized pigs have no apparent clinical disease"; (3) Variable systemic disease: Polyserositis and arthritis occur in only a portion of colonized pigs; (4) CNS disease recently reported: "fibrinopurulent meningitis, central nervous system inflammation, and clinical signs has been reported."
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. hyorhinis disease is not reportable; (2) Nursery disease: Primarily affects young pigs, resolves before market; (3) Endemic worldwide: Considered to have worldwide distribution.
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
Decreased susceptibility documented: (1) Resistance reported: "Decreased susceptibility or resistance to certain antimicrobial drugs has been suggested"; (2) Ongoing monitoring: "regular antimicrobial susceptibility monitoring takes place mainly in Europe"; (3) Variable patterns: "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 method: (1) No commercial vaccine: "Commercial vaccines for M. hyorhinis are currently not available"; (2) Antimicrobial reliance: "control efforts are primarily focused on the mitigation of clinical disease through antibiotic therapy"; (3) Autogenous vaccines limited: "Autogenous vaccines...have gained popularity...but efficacy evaluations...have not been performed or are not in the public domain."
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) Natural resistance: "Due to the lack of a cell wall, M. hyorhinis is naturally resistant to beta-lactams"; (2) Effective drugs: "M. hyorhinis is generally susceptible to macrolides, lincomycin, and tetracyclines."
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: No availability: Effective vaccines not currently available in the US (or have not been developed)
No commercial vaccines: (1) Not available: "Commercial vaccines for M. hyorhinis are currently not available"; (2) Autogenous vaccines unproven: "Autogenous vaccines for M. hyorhinis have gained popularity among certain production systems, but efficacy evaluations of such products have not been performed or are not in the public domain."
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Not feasible: Eradication extremely unlikely
Eradication not achievable: (1) Near-universal colonization: "almost 100% detection at the group level has been reported at the end of the nursery period"; (2) Persists after elimination efforts: "The bacterium can be detected in herds even after undergoing elimination efforts, including herd closure and antibiotic treatment"; (3) No published success: "Published reports of the successful elimination of M. hyorhinis from swine herds are not available."