Streptococcus suis infections in swine: Epidemiology, prevention, and zoonotic implications
Abstract
The purpose of the studies examining swine was to determine the sources of S. suis which colonize neonatal pigs; to determine the youngest age at which S. suis may be isolated from pigs; and, to evaluate medicated early weaning (MEW) as a preventive measure. Multiple samples were collected from pigs of all ages, their dams, and the environment. All collected samples were culturally examined for S. suis. Streptococcus suis isolates were serotyped and in some cases antimicrobial susceptibility tests were performed. Multiple serotypes of S. suis were isolated from samples collected from individual pigs. Streptococcus suis was isolated from saliva, nasal secretions, feces, and the underline of the sow at farrowing and thereafter. Streptococcus suis was isolated from pig samples collected at birth, but was not isolated from samples collected from cesarean derived pigs. In many cases, S. suis of the same serotype isolated from samples collected from the dam were detected in samples from that dam's pig. Additionally, the pig was colonized with S. suis of the same subtype(s) carried by the sow as determined by genomic fingerprinting. These results indicated that the primary source of S. suis was the sow, and that S. suis colonized the surface and oral cavity of the pig during the birth process when the pig contacted and swallowed infected sow vaginal secretions. Moreover, the pig was continually exposed to S. suis following birth when it contacted S. suis from sow excretions and secretions. Medicated early weaning of pigs with penicillin, ampicillin, or ceftiofur sodium failed to eliminate the tonsillar carrier state of S. suis . The use of antimicrobial susceptibility testing on herd isolates of S. suis is recommended due to the variability in sensitivity between isolates. Optimization of management and environment of pigs, coupled with strategic medication of clinically ill animals is recommended for control and prevention of mortality caused by streptococcosis. The purpose of the human study was to determine if people in Indiana were carriers of S. suis and at risk of contracting streptococcosis or infecting the pigs with which they worked. Human S. suis carriers were not identified.
Degree
Ph.D.
Advisors
Clark, Purdue University.
Subject Area
Veterinary services|Microbiology
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