A Bacteriological and Serological Survey of Actinobacillus (Haemophilus) pleuropneumoniae Serotype 5 in Nagasaki Prefecture

Abstract

The prevalence of antibodies to Actinobacillus (Haemophilus) pleuropneumoniae serotype 5 in NagasakiPrefecture of Japan was carried out by complement-fixation test. Serum samples were collected from 1658 pigs in 220 farms during the years 1983-86. Fifty-five strains of A. pleuropneumoniae isolated from pneumonic lesions during 1985 to 1987 were serotyped by coagglutination test.
The positive rate (titer≥1: 10) of antibodies to A. pleuropneumoniae serotype 5 were 9.0%(150/1658), and the antibody titer (geometric mean) of these positive sera were 1: 11.4. There was no difference between fattening pigs and breeding pigs. In breeding pigs, positive rates of antibodies to A. pleuropneumoniae serotype 5 were decreased gradually with advance in parity, while antibody titer (GM 1: 14.9) of raising pigs (female) in positive sera were higher than other groups (GM 1: 10.0 1: 11.5). The positive rates of antibodies to A. pleuropneumoniae serotype 5 in breeding pigs, produc ed out of Nagasaki Prefecture, were significantly higher than that in breeding pigs, produced in Nagasaki Prefecture, however, there was no difference in the antibody titer of positive sera. Fiftyfour (24.5%) of 220 pig farms had antibodies against A. pleuropneumoniae serotype 5.
The positive rate of antibodies to A. pleuropneumoniae serotype 2 were 56.8% in 1658 pigs and 80.5% in 220 farms examined. The geometric mean antibody titer of these positive sera were 1: 37.5.
Of 55 A. pleuropneumoniae strains, 7 (12.7%) were identified as serotype 5, and the other stains were identified as serotype 2.
Our results showed that a considerable number of pigs were infected with A. pleuropneumoniae serotype 5 in Nagasaki Prefecture, suggesting that many of these infected pigs have the potential for developing pleuropneumonia, or spreading A. pleuropneumoniae serotype 5 to other normal pigs. Further, it is possible that A. pleuropneumoniae serotype 5 infection may be spreading throughout in Japan.