The carriage of Streptococcus suis type 2 by pigs in Papua New Guinea

An indirect fluorescent antibody test was used to detect the presence of Streptococcus suis type 2 in nasal and pharyngeal swabs taken from pigs in Papua New Guinea. The rate of carriage for the two sites in domesticated indigenous village pigs was 0·5 and 2·5% respectively, compared to 39 and 43% for intensively reared pigs. These findings were supported by the results of a serological survey, using an enzyme linked immunosorbent assay, in which 87% of intensively reared pigs but only 8% of village pigs were seropositive to S. suis type 2. 
It is proposed that in intensive piggeries S. suis type 2 is continually cycled between pigs. In village pigs, the low population density and harsh environmental conditions prevents this cycle of infection.