Source and timing of Streptococcus suis infection in neonatal pigs: Implications for early weaning procedures

Sandra Faye Amass, DVM, MS; L. Kirk Clark, DVM, PhD; and Ching Ching Wu, DVM, PhD

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To determine the possible sources of Streptococcus suis that colonize neonatal pigs, and the youngest age at which S. suis may be isolated from pigs, multiple samples were collected from 35 pigs, their dams, and the environment. Streptococcus suis was not isolated from environmental samples collected before sows were placed in the harrowing house. At the day of harrowing and for 6 days thereafter, five pigs were euthanized daily and tonsils and meningeal swabs were collected from each pig .Additionally, multiple samples (sow vaginal swab, placental swab, milk, sow teat skin swab, sow feces, sow saliva, sow nasal secretions, piglet water, swab of piglet mat, environmental air) were collected at the time the pig was removed. All samples were culturally examined for S. suis. Streptococcus suis isolates were serotyped and antimicrobial susceptibility tests were performed. No conclusions were drawn from the meningeal swab samples; cultural examination confirmed that they had become contaminated during sampling. Forty-five isolates of S. suis serotypes 1-8 were isolated. The most prevalent serotype of S. suis isolated was serotype 3 (33.3%), followed by 5 (22.2 %), 7 ( 17. 8%), 4 ( 1.1%), 6 (6.7%), 8 (6.7%), and 2 (2.2%). Often (six of seven dams), multiple serotypes of S. suis were isolated from samples collected from a single dam. Streptococcus suis was isolated from samples of sow origin beginning on day 0 (two of seven sows), and the tonsils of pigs as early as day 1 (two of five pigs). In four of seven dams, S. suis of the same serotype isolated from samples collected from the dam was detected in samples of the tonsil of that dam,s pig. These results suggest that the source of S. suis was the sow, and that S. suis could have colonized the tonsil of the pig shortly after birth when the pig contacted sow excretions and secretions. Ninety-one percent of the S. suis isolates were susceptible to ampicillin. Less than 50% of these isolates were susceptible to apramycin, lincomycin, penicillin, spectinomycin, tetracycline, and tylosin. Consequently, the use of antimicrobial susceptibility testing on herd isolates of S. suis is recommended due to the variability in sensitivity between isolates.

Keywords: Streptococcus suis, neonatal, early weaning

RIS citationCite as: Amass SF, Clark LK, Wu CC. Source and timing of Streptococcus suis infection in neonatal pigs: Implications for early weaning procedures. J Swine Health Prod 1995;3(5):189-193.

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