Streptococcus suis infections in Danish pigs and experimental infection with Streptococcus suis serotype 7

During a two-year period, Streptococcus suis serotypes 1-8 were isolated from 108 pigs examined at the laboratory. S. suis serotypes 2 and 7 represented 75% of the isolates. S. suis serotype 7 was isolated more frequently than reported from other countries, and mostly from piglets less than 3 weeks of age. Experimental inoculation of 7-day-old piglets with S. suis serotype 7 provoked severe illness within a week in 6 out of 7 animals. By bacteriological and pathological examination it was found that S. suis serotype 7 was pathogenic to piglets, giving rise to septicemia with predilection for joints, serous membranes and meninges.