Identification of Streptococcus suis carriage in healthy pigs in Chiang Mai, Thailand
Authors:   Integrative Research Centre for Veterinary Preventive Medicine, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand, Kittiwan Nattinee ,   Department of Food Animal Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand, Tadee Pakpoom ,   Integrative Research Centre for Veterinary Preventive Medicine, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand,   Department of Food Animal Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand, Tadee Phacharaporn ,   Faculty of Animal Science and Technology, Maejo University, Chiang Mai 50290, Thailand, Buawiratlert Tunyamai ,   Integrative Research Centre for Veterinary Preventive Medicine, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand,   Department of Food Animal Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand, Eiamsam-ang Thanaporn ,   Integrative Research Centre for Veterinary Preventive Medicine, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand,   Department of Food Animal Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand, Boonma Orawan ,   Diagnostic Section, Veterinary Research and Development Center (Upper Northern Region), Hang Chat, Lampang 52190, Thailand, Rojanasthien Suvichai ,   Akkhararatchakumari Veterinary College, Walailak University, Nakhon Si Thammarat 80160, Thailand, Pascoe Ben ,   The Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, UK, Patchanee Prapas Patchanee ,   Integrative Research Centre for Veterinary Preventive Medicine, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand,   Department of Food Animal Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand
Published: April 2022

Streptococcus suis (S. suis) belongs to the critical streptococcal swine pathogens affecting financial losses in pig production globally and being concerned as a zoonotic bacterial that causes a severe invasive disease emerging in pigs and humans. Serotype 2 is considered the major serotype and is the most pathogenic S. suis obtained from human cases, and the healthy pigs are known as the major reservoir of S. suis. In this cross-sectional study, S. suis prevalence was conducted in live pigs from 111 farms across Chiang Mai, Thailand. S. suis carriage rate and serotypes were determined from the bacteriological and multiplex PCR method from tonsil swab samples. We found that 18.2% (138/760) of tonsil swab samples and 54.1% (60/111) of pig farms were positive to S. suis, and only one (0.72%) from 138 isolates was identified as serotype 9. Meanwhile, all the remains were identified as non-serotype ½/1/2/7/9/14 strains. In addition, there was an independent relation between age-ranged, farm types, and production systems with S. suis-positive rates at the farm level. The results indicate that both intensive and smallholder production systems can generally be the source of S. suis carriage. Therefore, implementing good husbandry practices and S. suis-infection predisposing factors limiting that appropriate for each farm type is essential to minimize the opportunities of S. suis outbreak in humans.