Streptococcus R (Streptococcus suis type II) infection in pigs in Japan

Since the first outbreak of an epizootic disease on a pig farm in Shimane Prefecture in 1979, similar diseases have occurred continually on other 8 pig farms in the same prefecture until 1982. Main clinical symptoms of the disease were recumbency, convulsion, anorexia and paddling. The diseased pigs ranged mostly from 35 to 67 days of age. Monthly fatality on one pig farm for 1 year was 0.2 to 3.6%. Morbidities in affected litters were mostly at a level of 20 to 30% on 7 pig farms. The diseases were diagnosed as streptococcal meningitis and septicemia with each one of endocarditis and pneumonitis by pathological and bacteriological studies on 20 affected pigs. Distribution of piglets from a breeding farm to pig farms was considered as one of the causes of prevalence in the prefecture. Representative 20 strains of the isolates from diseased animals on 9 pig farms were identified as Streptococcus R (Streptococcus suis type II) by biological and serological examinations. For the latter examination, anti-Streptococcus R, S and T sera were prepared. It was also indicated that the disease had occurred in 8 prefectures in addition to Shimane, because positive results had been obtained from 41 strains submitted from those prefectures for serological diagnosis. The minimal inhibitory concentration was examined in 18 drugs to 19 isolates. It was the lowest in ampicillin and thiopeptin of all the drugs.