Prevalence of Streptococcus suis in Tonsils of Slaughtered Pigs in Lampang and Phayao Provinces, Thailand, 2009-2010

Abstract

Abstract

Streptococcus suis, a swine and human pathogen, may be the cause of high prevalent, sporadic, human cases in northern Thailand. A survey of S. suis from the tonsils of slaughtered pigs was conducted in Lampang and Phayao provinces, Thailand, during September 2009-July 2010. Samples of pigs from slaughterhouses of the respective provinces were cultured. S. suis was isolated and identified by conventional method and PCR using primers specific to 16S rRNA, and capsular gene types 1(14) and 2(1/2). Additional confirmation was obtained by slide agglutination and capillary tube precipitation with S. suis type 1, 2 and 14 antisera. The results of tonsil samples of 236 pigs from Lampang were positive for S. suis, S. suis type 2, and S. suis type 14, at rates of 64.8%, 3.8%, and 2.1%, respectively. Tonsil samples of 559 pigs from Phayao were positive for S. suis, S. suis type 2, and S. suis type 14, at rates of 61.4%, 5.9%, and 1.2%, respectively. There was no significant difference among the prevalence of S. suis in pig tonsils and the ambient temperature and humidity (p > 0.05). The results of the investigation of virulence-associated genes included suilysin (sly), muramidase released protein (mrp) and extracellular protein factor (epf); of 151 S. suis isolates from Phayao, genotypes with sly+, mrp+ and epf+ were detected in 64.9%, 58.9%, and 3.9%, respectively. The high prevalence of S. suis carrier in pigs, especially serotypes 2 and 14, and the presence of virulence-associated genes may be risk factors for S. suis infection in humans.

Keywords: Streptococcus suis, tonsils, pigs, Lampang, Phayao, Thailand