It’s not unrealistic to say that if you checked the nasal cavities or tonsils of any group of pigs, you would find Streptococcus suis (Strep suis). While the strain and impact can vary widely, this commensal bacterium is on virtually every hog farm. 

“There are differences as far as prevalence for strains when you look across the US and the world, but that changes as immunity waxes and wanes,” Matt Sturos, DVM, veterinary pathologist, University of Minnesota, told Pig Health Today. “That also changes as the bacteria move around and evolve.”