In swine, Streptococcus dysgalactiae group C serovars are β-hemolytic and are commonly found in nasal and throat secretions, tonsils, and vaginal and preputial secretions. They are the most important β-hemolytic streptococci involved in lesions in pigs. Vaginal secretions and milk from postparturient sows are the most likely sources of infection in piglets. Streptococci enter the bloodstream via skin wounds, the navel, and tonsils. A bacteremia or septicemia occurs, and the organisms then settle in one or more tissues, giving rise to arthritis, endocarditis, or meningitis.
Clinical Findings and Lesions
Infection is usually first seen in pigs 1–3 wk old. Joint swelling and lameness are the most obvious and persistent clinical signs. Elevated 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 streptococcal septicemia, arthritis, or endocarditis is best accomplished by necropsy and bacteriologic examination of affected pigs. Only small numbers of organisms or no organisms may be isolated from affected joints, especially when inflammation is advanced.
Treatment and Prevention
β-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 recent reports about vaccination against these streptococci. Autogenous bacterins have been used, and there are reports of a reduction in incidence of arthritis when sows were vaccinated before farrowing.
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 is not recognized as a zoonotic pathogen.
Last full review/revision March 2012 by Darryl Ragland, DVM, PhD