Detection of Japanese spotted fever rickettsiae DNA from ixodid ticks and seasonal occurrence of ixodid tick population on the Osumi Peninsula, Kagoshima Prefecture

摘要

In the present study, we attempted to detect Rickettsia japonica DNA from ixodid ticks by the PCR technique. The seasonal occurrence of ixodid ticks was also examined in the endemic area of Japanese spotted fever. Ixodid ticks were collected at 14 sites, Futagawa (two sites), Uto, Arahira, Kamitakakuma (two sites), Onohara, Yadorihara (four sites) and Kamikawa (three sites), on the Osumi Peninsula, Kagoshima Prefecture in May and June 2001, and also collected additionally at Onohara and Kamikawa in May 2002. A total of 767 ixodid ticks was collected. They were identified as three genera and eight species as follows: Haemaphysalis flava, H. formosensis, H. longicornis, H. hystricis, Ixodes ovatus, I. nipponensis, I. turdus, and Amblyomma testudinarium. H. flava and H. longicornis seemed to be the dominant species in the survey areas. With a primer pair Rl, R2, which amplifies the genomic DNA from the spotted fever group rickettsiae, an approximately 540 bp fragment was amplified from 15 samples of six sites; H. flava (seven samples), H. longicornis (three samples), H, hystricis (four samples) and A. testudinarium (one sample). With a primer pair Rj5, Rj10, which amplifies the genomic DNA only from R. japonica, a 357 bp fragment was amplified from four samples of three sites; H, flava (three samples) and H. hystricis (one sample), H. flava seems to be the most important vector tick for Japanese spotted fever in Kagoshima Prefecture, Seasonal occurrence of the ixodid population was surveyed at threesites, Takatoge, Onohara and Komagahara from May 2002 to April 2003 H. flava nymphs were collected throughout the year, and a large number of nymphs was collected in spring. Adults showed a similar fluctuation pattern to the nymphal pattern. A large number of adults was collected from February to April but not in August and September.