Usefulness of polymerase chain reaction (PCR) in diagnosis of infections caused by Leptospira spp. in swine

摘要

Leptospirosis can be an important problem and a cause of significant economic losses in swine herds. Because of a high susceptibility of leptospires to many factors, laboratory diagnosis of the disease (especially pathogen isolation and identification) is difficult and often based on serological methods. The aim of this study was to show the possible use of PCR for detection and partial identification of Leptospira spp. in clinical samples from swine. Four aborted fetuses and 2 serum samples from sows reared on a farm infected by the serovar Pomona and 4 fetuses from a farm infected by leptospires from the serogroup Sejroe were submitted for examination. Additionally, urine and serum samples from 8 aborting sows reared on 2 farms infected by the serogroup Sejroe were investigated. Serum samples were examined by the microagglutination test (MAT). Samples of urine and tissue samples from fetuses were examined by PCR with pairs of primers detecting DNA sequences specific to a) genus Leptospira, b) species L. borgpetersenii, c) two selected groups of serovars of the species L. interrogans, d) serogroup Sejroe. Serological findings showed in all examined sows the presence of titers to the serogroup Pomona or Sejroe, depending on the serogroup causing infection on a given farm. DNA of the genus Leptospira was detected in tissues of all fetuses from sows infected by the serovar Pomona, in 3 fetuses from the farm infected by the Sejroe serogroup, and in all urine samples. The presence of the DNA sequence specific for the group of L. interrogans serovars including the serovar Pomona was found in tissues of all 4 fetuses from dams presenting titers to the serogroup Pomona. DNA of the serogroup Sejroe was detected in 6 out of 8 urine samples examined, and DNA of the species L. borgpetersenii (including the serovar Sejroe) was found in 5 urine samples. No DNA of the species L. borgpetersenii or of the serogroup Sejroe was found in tissues of fetuses from the farm infected by the serogroup Sejroe. This study demonstrated the usefulness of PCR in confirming the presence of Leptospira spp. in clinical samples from swine. Furthermore, PCR confirmed the presence of the serovar Pomona in tissues of aborted fetuses and the presence of L. borgpetersenii and/or the Sejroe serogroup in samples of urine. A conclusive evaluation of the usefulness of PCR in identifying DNA of L. borgpetersenii and the serogroup Sejroe in tissue samples requires further investigations.