STREPTOCOCCUS DYSGALACTIAE SUBSP. EQUISIMILIS
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; 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; Minimal risk: Agent inherently unlikely to develop clinically important resistance to antibacterial or antiviral treatments; Minimal risk: Antibacterial or antiviral treatments rarely occur, or are typically limited to short-course individual animal therapy; 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; Not feasible: Eradication extremely unlikely
OVERVIEW
Streptococcus dysgalactiae subsp. equisimilis is a beta-hemolytic streptococcus belonging to Lancefield groups C, G, or L that is part of normal swine microbiota. It is common in nasal and throat secretions, tonsils, and vaginal and preputial secretions. The organism causes arthritis, endocarditis, and meningitis primarily in pigs 1-3 weeks of age. Vaginal secretions and milk from postparturient sows are the most likely sources of infection for piglets. Streptococci enter the bloodstream via skin wounds, the navel, and tonsils. A 7-year Japanese study found S. dysgalactiae represented 77.6% of beta-hemolytic streptococci from slaughtered pigs. Early lesions include periarticular edema, swollen synovial membranes, and turbid synovial fluid; chronic lesions show articular cartilage necrosis and fibrosis. Prevention focuses on adequate colostral intake and minimizing traumatic injuries to feet and legs. Autogenous bacterins in sows before farrowing have reduced arthritis incidence.
FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No controls necessary
S. dysgalactiae subsp. equisimilis in pigs is not associated with foodborne transmission to humans.
NON-FOODBORNE ZOONOTIC TRANSMISSION POTENTIAL
Level: Highly unlikely: No evidence of non-foodborne zoonotic transmission
This subspecies in swine is not associated with human disease transmission. Human S. dysgalactiae infections are typically from other sources.
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 through direct contact within farms: (1) Sow-to-piglet transmission: "vaginal secretions and milk from postparturient sows are the most likely sources of infection for the piglets"; (2) Entry through wounds: "Streptococci enter the bloodstream via skin wounds, the navel, and tonsils"; (3) Normal flora: Part of normal swine microbiota.
DIFFICULTY OF DETECTING AND CONFIRMING INFECTION
Level: Easy: Distinct clinical signs and/or existing test(s) available at local/regional laboratory(s)
Clinical presentation and culture: (1) Characteristic age/signs: "Infection is usually first seen in pigs between 1 and 3 weeks of age. Joint swelling and lameness are the most obvious and persistent clinical signs"; (2) Culture: Beta-hemolytic streptococci readily cultured from joints and lesions; (3) Lancefield grouping: Identified by Lancefield groups C, G, or L.
FINANCIAL IMPACT ON FARM'S COST OF PRODUCTION
Level: Moderate: Manageable losses related to endemic (population) or chronic (individual) occurrence
Sporadic losses in young pigs: (1) Common cause of lameness: "in lame pigs up to 12 weeks of age, the most common causative agent was S. dysgalactiae subsp. equisimilis"; (2) Culling: "most of the pigs culled for arthritis were under 6 weeks of age"; (3) Endemic but manageable: Part of normal flora causing opportunistic infections.
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) Endemic commensal: Normal flora worldwide; (2) Not regulated: Not a reportable disease.
PATHOGEN'S ABILITY TO DEVELOP AND SPREAD RESISTANCE
Level: Minimal risk: Agent inherently unlikely to develop clinically important resistance to antibacterial or antiviral treatments
Beta-hemolytic streptococci generally susceptible: "Beta-hemolytic streptococci are sensitive to beta-lactam antibiotics." While high MICs to some drugs reported, beta-lactams remain effective.
AMR DEVELOPMENT DRIVEN BY DISEASE MANAGEMENT
Level: Minimal risk: Antibacterial or antiviral treatments rarely occur, or are typically limited to short-course individual animal therapy
Prevention-focused control: (1) Individual animal treatment: Treatment of affected individuals rather than mass medication; (2) Prevention emphasis: "Adequate intake of colostrum may ensure that the piglets receive protective antibodies."
AVAILABILITY OF EFFECTIVE TREATMENT OPTIONS
Level: Available but with uncertain efficacy: Limited treatments available in US or are only effective in some situations
Early treatment effective: (1) Beta-lactams effective: "Beta-hemolytic streptococci are sensitive to beta-lactam antibiotics"; (2) Early treatment important: "Long-acting antibacterial agents may be beneficial, and treatment should be given before the inflammatory process is well advanced."
AVAILABILITY OF EFFECTIVE VACCINES OR BACTERINS
Level: Available but uncertain efficacy: Commercial or autogenous vaccines exist in the US but protection may be inconsistent
Autogenous vaccines available: (1) Sow vaccination: "Autogenous bacterins have been used, and a reduction in the incidence of arthritis has been reported when sows were vaccinated before farrowing"; (2) No commercial vaccines: "There are no recent reports about vaccination against groups C or L streptococci."
FEASIBILITY OF ERADICATING THE DISEASE FROM THE US
Level: Not feasible: Eradication extremely unlikely
Eradication not feasible: (1) Normal flora: "members of the S. dysgalactiae subsp. equisimilis species are all beta-hemolytic streptococci...members of the normal swine microbiota"; (2) Ubiquitous: Present in virtually all pig herds; (3) Opportunistic pathogen: Disease occurs when predisposing factors present.