Streptococcus suis in free-ranging wild boars from Southern Brazil: A preliminary survey

Streptococcus suis (S. suis) is a pathogen associated with pigs and human meningitis. Previous studies indicate wild boars (Sus scrofa) as a S. suis reservoir; however, in Brazil this has not yet been assessed in free-ranging wild boars. Therefore, this study aimed to identify the frequency of S. suis in wild boar samples from South Brazil. For that, convenient lung and lymph node samples collected during 2013, 2014, 2015, and 2019 of free-ranging wild boars from Rio Grande do Sul, South Brazil were evaluated. The detection of S. suis was based on the presence of gdh (glutamate dehydrogenase) gene by real-time PCR. Histopathological and immunohistochemical (IHC) analyses were performed to identify lesions associated with the presence of S. suis in positive samples. The results revealed S. suis gdh detection in 4% (5/78) of lung samples and 1.05% (1/95) of lymph node samples. All of the positive animals were from an environmental reserve in Barra do Ribeiro city. No association of S. suis DNA, antigen or lesions was identified in the positive animals. Although there are some limitations due to convenience sampling, lack of upper respiratory samples, and specific geographic localization, this study provides the first insights into the frequency of S. suis in Brazil.