In swine, beta-hemolytic Streptococcus dysgalactiae equisimilis usually belong to Lancefield group C. Although members of the normal flora, they are considered the most important beta-hemolytic streptococci involved in lesions in pigs. These streptococci are common in nasal and throat secretions, tonsils, and vaginal and preputial secretions. Vaginal secretions and milk from postparturient sows are the most likely sources of infection for the piglets.
Clinical Findings and Lesions in S. dysgalactiae subsp. equisimilis Infection in Pigs
S dysgalactiae equisimilis infection is usually first seen in piglets 1–3 weeks old. Joint swelling and lameness are the most obvious and persistent clinical signs. Increased temperatures, lassitude, roughened hair coat, and inappetence may also be noted. Early lesions consist of periarticular edema; swollen, hyperemic synovial membranes; and turbid synovial fluid. Necrosis of articular cartilage may be seen 15–30 days after onset and may become more severe. Fibrosis and multiple focal abscessation of periarticular tissues and hypertrophy of synovial villi also occur. Endocarditis occurs but is difficult to diagnose antemortem. Lesions consist of yellow or white vegetations of different sizes, often covering the entire surface of the affected valve.
Diagnosis of S. dysgalactiae subsp. equisimilis Infection in Pigs
A presumptive diagnosis can be made based on the clinical signs and age of the affected piglets. Confirmation is by bacterial culture of lesions at necropsy.. Only small numbers of organisms or no organisms may be isolated from affected joints, especially when inflammation is advanced.
Treatment and Prevention of S. dysgalactiae subsp. equisimilis Infection in Pigs
Beta-hemolytic streptococci are sensitive to beta-lactam antibiotics. Long-acting antibacterial agents may be beneficial, and treatment should be given before inflammation is well advanced. There are no commercial vaccines, but autogenous bacterins are sometimes given to prefarrowing sows to attempt to reduce incidence of arthritis in piglets.
Adequate intake of colostrum may ensure that piglets receive protective antibodies. Traumatic injuries to the feet and legs should be minimized by reducing the abrasiveness of the floor surface in the farrowing area.
S dysgalactiae equisimilis are beta-hemolytic streptococci that cause arthritis, endocarditis, or meningitis in young piglets.
Beta-lactam antibiotics are the recommended treatment.
Traumatic injuries to the feet and legs of piglets can be minimized by reducing abrasiveness of flooring and can help avoid infection.