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Streptococcus dysgalactiae equisimilis Infection in Pigs


Marcelo Gottschalk

, DVM, PhD, Department of Pathology and Microbiology, Faculty of Veterinary Medicine, University of Montreal

Reviewed/Revised Jan 2024

Streptococcus dysgalactiae equisimilis in swine belong mostly to Lancefield group C. Infection may result in arthritis, endocarditis, and meningitis in very young piglets. The bacteria are also found as normal flora in adult pigs. Treatment is with beta-lactam antimicrobials and should be given before extensive inflammation occurs. There are no commercial vaccines, but autogenous bacterins have decreased the incidence of arthritis in piglets.

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 pathological 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 equisimilis Infection in Pigs

Streptococcus dysgalactiae equisimilis infection is usually first observed 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 evident 15–30 days after onset and may become more severe. Fibrosis and 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 equisimilis Infection in Pigs

A presumptive diagnosis of S dysgalactiae equisimilis infection 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 equisimilis Infection in Pigs

Beta-hemolytic streptococci such as S dysgalactiae equisimilis are sensitive to beta-lactam antimicrobials. Long-acting antibacterial agents may be beneficial, and treatment should be given before inflammation is well advanced. There are no commercial vaccines; however, autogenous bacterins are sometimes given to prefarrowing sows to attempt to decrease 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 decreasing the abrasiveness of the floor surface in the farrowing area.

Key Points

  • S dysgalactiae equisimilis are beta-hemolytic streptococci that cause arthritis, endocarditis, and meningitis in young piglets.

  • Beta-lactam antimicrobials are the recommended treatment.

  • Traumatic injuries to the feet and legs of piglets can be minimized by decreasing abrasiveness of flooring and can help avoid infection.

For More Information

  • Gottschalk M, Segura M. Streptococcosis. In: Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW, Zhang J, eds. Diseases of Swine. 11th ed. Wiley-Blackwell; 2019:934–950. doi:10.1002/9781119350927.ch61

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