Yumiko Furuya

Occurrence of high ratio of males after introduction of minocycline in a colony of leptotrombidium fletcheri infected with orientia tsutsugamushi

In colonies of Leptotrombidium fletcheri mites infected with Orientia tsutsugamushi (Ot), the agent of scrub typhus, males rarely appear. In the present study, the development of a high ratio of males was observed after introduction of minocycline (MC). A high dose of MC was injected subcutaneously into a mouse, and by feeding unfed larvae from an infected mite colony on this mouse, the Ot in the mites were successfully killed. Of a total of 130 unfed larvae attached to the mouse, 29 developed into females; of these, 9 laid an average of 112.4 eggs/female. Unfed larvae in the succeeding generations were attached to untreated mice. All adults in the P and F1 generations were females, and males started to appear at the F2 generation. The ratio of males to females was 332:7, 108:13, 263:61 and 71:9 at the F2, F3, F4 and F5 generations, respectively. These data suggest that Ot in the ovary or gonad may suppress the development of males.

Mite Vectors (Acari: Trombiculidae) of Scrub Typhus in a New Endemic Area in Northern Kyoto, Japan

Abstract Between 1983 and 1999, 27 human cases of scrub typhus (two fatal) occurred in the Nodagawa River basin of northern Kyoto, Japan, an area where no cases had been previously reported. Antibody screening of infected patients’ sera showed that nine of 15 patients had high titers against the Gilliam type of Orientia tsutsugamushi (Hayashi). To determine the vector mite transmitting the disease, we studied rodent and chigger populations in and near a rice field alongside the Nodagawa River between 1996 and 1999. The most common rodent species was Microtus montebelli (Milne-Edwards), representing 73.3% (33/45) of the population. The mite index (average number of mites per infested host) was highest (190.8) in Leptotrombidium pallidum Nagayo, Mitamura & Tamiya parasitizing on M. montebelli, followed by Leptotrombidium intermedium (Nagayo, Mitamura & Tamiya) (174.9) on the same host species. Orientia tsutsugamushi was isolated from 60.5% (23/38) of rodents and from 71.2% (37/52) of pools of engorged L. pallidum. The Gilliam type of O. tsutsugamushi was most prevalent in rodents, and in engorged L. pallidum and it was the only type recovered from 10 isolates inoculated into L 929 cells for indirect immunofluorescence examination. Orientia tsutsugamushi infected 14.3% (181/1263) and 14.8% (306/2066) of engorged and unfed L. pallidum larvae, respectively, and was also detected in 0.055% (2/3634) of unfed L. intermedium, although previous studies suggest that this mite rarely bites humans. These results show that L. pallidum is the primary vector species of scrub typhus in this new endemic area in Japan.

神奈川県域の感染性胃腸炎患者からのパレコウイルスの検出―平成20 年度から平成22 年度の病原体定点医療機関からの 検体について―

To clarify the causative viruses of infectious gastroenteritis, fecal specimens were sent from the pediatric sentinel clinic in Kanagawa Prefecture except for Kawasaki City, Yokohama City, Yokosuka City, Sagamihara City, and Fujisawa City. About 50% of fecal specimens were not negative for causative viruses. A total of 374 fecal specimens which were known to be negative for rotavirus, adenovirus, norovirus, sapovirus, and astrovirus were tested for human parechovirus (HPeV). HPeVs VP1 genes were detected in 15 samples from 374 fecal specimens which were tested from April 2008 to March 2011. Sequencing analysis of a 800-nt portion of the HPeV VP1 gene of these 8 strains and 7 specimens from April 2008 to March 2011 showed that one specimen in Septenber 2008 was classified as HPeV4 and 14 of the others were classified as HPeV1.

[Characterization of anti-HBs antigen monoclonal antibodies and application to subtyping].

Several monoclonal antibodies were produced against purified HBs antigens, subtype adr adw and ayw. The subtype specificity of these nine antibodies was characterized by the passive hemagglutination inhibition method. The specificity of these anti-HBs monoclonal antibodies was analyzed with use of 31 HBs antigen panels. Five of the nine monoclonal antibodies had a specificity against the group a-determinant of HBs antigen. Two antibodies were demonstrated to have anti-r specificity and another two were anti-w.One of these anti-a monoclonal antibodies, in its reaction pattern, resembled anti-a polyclonal antibady derived from human serum. This anti-a monoclonal antibody was used as the standard to determine HBs antigen subtyping, The results nearly agree perfectly with results obtained when anti-a polyclonal antibodies were used as the standard.Using these monoclones, we analysed HBs antigen subtypes of asymptomatic carriers. Although the antigen titer changed at various time in each parson, the ratio of each subtype determinant was unchanged. However, three anti-a monoclonal antibodies showed a different reaction pattern against “a” determinant of individual carriers, and therefore “a” determinant of HBs antigen might be subdivided, and should be analyzed in more detail by monoclonal antibodies.