Meningitis Caused by Streptococcus suis in Humans

Between 1968 and 1984, 30 strains of Streptococcus suis causing meningitis were isolated in the Netherlands. Twenty-eight strains were type 2, one was type 4, and one was untypable. The average age of the patients infected with these strains was 49 years (range, 21-76 years); the male-to-female ratio was 6.5. Twenty-five patients (83%) were employed in the pork industry. Two patients (7%) died. In seven cases (23%), predisposing factors were identified. The most frequent sequela was hearing loss (54% of surviving patients). The data for these 30 patients were compared with those for 30 patients from outside the Netherlands whose cases of meningitis due to S. suis type 2 were described between 1968 and 1985. No differences were found. The estimated annual risk of developing S. suis meningitis among Dutch abattoir workers and pig breeders was approximately 3.0/100,000--a rate 1,500 times higher than that among persons not working in the pork industry.