Mulberry heart disease persists among young pigs in Denmark although abundant supplies of selenium and vitamin E are added to feedstuffs for sows and pigs. The concentrations of selenium and vitamin E in the liver and heart tissues of young pigs which had died suddenly, and had the characteristic lesions of mulberry heart disease post mortem, were not significantly different from the concentrations found in pigs of the same age which had died suddenly for other reasons. The concentrations of selenium and vitamin E in the livers (0.3 mg/kg and 4 mg/kg, respectively) appeared to be satisfactory in all the pigs examined.
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.