Investigating the tonsillar viral profile of nursery pigs in farms with outbreaks of Streptococcus suis

Streptococcus suis disease is complex and little is known about viral factors and their impact on clinical outcome. In the first study, a subset of 25 cases and 27 controls were screened for the presence of influenza A virus (IAV), porcine circovirus 2 (PCV-2), porcine respiratory and reproductive syndrome virus (PRRSV), porcine parvovirus (PPV), hemagglutinin encephalomyelitis virus (PHEV) and swine cytomegalovirus (SCMV) in their tonsils using polymerase chain reaction. A majority of S. suis cases and healthy controls were SCMV-positive pigs, including 52% of all cases and 67% of controls. In the second study, we investigated the association between tonsillar viral metagenome and S. suis disease in 27 clinically affected nursery pigs and 29 healthy, age-matched controls. We identified the importance and functional relationship of viral families such as Podoviridae, Smacoviridae, Astroviridae as well as species richness for improving the predictability of S. suis clinical disease.