Streptococcal infections in sucking pigs. 1. Epidemiological investigations.

The investigation comprises 5,811 litters and 55,641 liveborn pigs. Among the pigs which died before weaning, infection with haemolytic streptococci (HS) was determined in 1,338. This corresponds to 2.4 per cent of the liveborn pigs (Table I). In the examined herds the incidence of fatal cases with HS infections ranged from 1.2 to 3.8 per cent. The highest incidence was observed in litters born by gilts (Table II) and in litters with more tha 11 pigs (Table III). HS infections were identified in 17.5 per cent of the examined litters, and in most of the litters only one pig was lost (Table IV). A marked seasonal variation was observed, with a predominance of HS during the winter period (Table V). Analyses of the influence of some possible determinative factors revealed the highest incidence among the progeny of sows which were housed separately during pregnancy (Table VI), whereas herd size and the hygiene level did not exert any influence on the frequency of HS. The incidence of fatal HS infections was higher in herds where tail docking and clipping of the canine teeth were performed than in herds where these procedures were omitted (Table VII). Most of the death with HS infections (53.8 per cent) occurred among pigs less than 14 days of age (Table VIII). The main diagnoses of the pigs with streptococcal infections are presented in Table IX. A survey of the isolation frequency of HS from various organs is given in Table X. The most frequently isolated serogroups were group-C (40.2 per cent) and group-L (31.3 per cent) (Table XI). Preliminary investigations on the source of infection and the pathogenesis are reported (Tables XII and XIII). In two herds, 8 of 10 sows carried HS on mucosal surfaces at the time of farrowing, and in 6 of 10 examined litters, HS bacteraemias were observed in pigs during the first days of life. Furthermore, an analysis showed that part of the sowa (109) lost pigs with HS infections in several (2-6) subsequent litters (Tables XIV) and XV).