Trombiculid Mites (Acari: Trombiculidae) and Rickettsia tsutsugamushi Isolated from Wild Rodents in a New Endemic Area of Japan

Abstract

Investigations of trombiculid mites and Rickettsia tsutsugamushi in wild rodents were made in southern Gifu Prefecture where patients infected with tsutsugamushi disease recently have been found. A total of 16,396 trombiculid mites, consisting of 10 species from three genera, was collected from 170 Apodemus speciosus in two locations. Kani-Sakahogi and Kuze. Leptotrombidium scutellare (Nagayo et al.) (44.0%) was most predominant, followed by L. pallidum (Nagayo et al.) (26.9%); L. fuji (Kuwata et al.) (13.6%); and Gahrliepia saduski Womersley (14.2%). These four species constituted the bulk of the chigger mite fauna. L. scutellare was present from October to February with a remarkably high peak in November, whereas pallidum occurred from November to March with the highest peak in December. L. fuji and G. saduski showed their highest peaks in December and moderate peaks in early summer (April and May). Positive identification of Rickettsia tsutsugamushi in wild rodents from Kani-Sakahogi were found to be 50 and 58.3% in November 1985 and 1986, respectively, and 38.5% in November 1986 from Kuze. R. tsutsugamushi was isolated from chigger mites of an L. pallidum-rich group, displaying the highest titer to Karp strain. Serological investigation of rodents to R. tsutsugamushi antibodies were calculated as 41.6 and 50% positive in November 1985 and 1986 in Kani-Sakahogi, respectively, and 50% in November 1986 in Kuze. The Karp strain was dominant in specificity to antibodies. These results indicate that the surveyed areas have a high probability of occurrence of tsutsugamushi disease, and L. scutellare and L. pallidum may serve as the vectors in these areas. Particularly, we suggest that L. scutellare is the most important vector which has caused a recent outbreak of this disease in southern Gifu Prefecture.

Transmission of Rickettsia tsutsugamushi strains among humans, wild rodents, and trombiculid mites in an area of Japan in which tsutsugamushi disease is newly endemic

“…Isolation of R. tsutsugamushi. To isolate local strains of R tsutsugamushi, blood samples from patients, spleen homogenates from wild rodents (A. speciosus), and whole-body homogenates of larval mites (L. pallidum) were injected intraperitoneally into ddY mice, as previously described (2). Briefly, blood samples were collected from patients who had high fevers and skin eruptions.…”

Analysis of ectoparasites (chigger mites, gamasid mites, fleas and sucking lice) of the Yunnan red‐backed vole (Eothenomys miletus) sampled throughout its range in southwest China

“…Some ectoparasites are vectors of zoonotic infections and thus play important roles in the transmission of a wide variety of diseases. Chigger mites (belonging to the families Trombiculidae and Leeuwenhoekiidae) are vectors of scrub typhus (tsutsugamushi disease) caused by the pathogen Orientia tsutsugamushi (Varma & Mahadevan, 1973;Asanuma et al, 1974;Traub & Wisseman, 1974;Walker et al, 1975;Roberts et al, 1977;Iwasa et al, 1990;Li et al, 1997;Lee et al, 2009). Some species of gamasid mite have been suspected to be potential vectors or reservoir hosts of haemorrhagic fever with renal syndrome (HFRS), also called epidemic haemorrhagic fever (EHF), and some other zoonoses (Deng et al, 1993;Song, 1999;Huang & Guo, 2010).…”

Virulence in Mice of Orientia tsutsugamushi Isolated from Patients in a New Endemic Area in Japan

“…In Gifu Prefecture, located in the center of Honshu island, the first case of tsutsugamushi disease was diagnosed in 1982, and since then 13-56 patients a year have been reported in the region (7). We elucidated endemic strains of Orientia tsutsugamushi isolated from patients, wild rodents and trombiculid mites in Gifu Prefecture (6,8). Four of six new strains have been isolated from patients, i.e., KN-1 (identified as Kawasaki type), GJ-1 (identified as Kuroki type), KN-2 and KN-3, all of which can be distinguished antigenically from each other (17,18).…”