Jpn. J. Infect. Dis., 53 (2), 77-78, 2000
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Laboratory and Epidemiology Communications
Occurrence of Scrub Typhus (Tsutsugamushi)
in Kanagawa Prefecture and Types of Orientia tsutsugamushi
Involved
Yumiko Furuya*, Takashi Katayama, Miyuki Hara, Yoshiya
Yoshida, Mitsunobu Imai and Toshikatsu Hagiwara1
Kanagawa Prefectural Public Health Laboratory, Nakao 1-1-1, Asahi-ku, Yokohama 241-0815 Kanagawa and 1National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku 162-8640 Tokyo
Communicated by Shigetou Suzuki
(Accepted May 9, 2000)
Scrub typhus, or Tsutsugamushi disease, is caused by Orientia tsutsugamushi. Kanagawa Prefecture near Tokyo experienced a large epidemic of scrub typhus in 1988-1989. It then wanned: in 1996 only 9 cases were reported. However, the epidemic now appears to be in resurgence. From April 1997 to March 1998, 17 clinical cases were reported. From April 1998 to March 1999, 21 cases were reported, and from April 1999 to March 2000, 43 cases were reported. The infection was most frequent in November. In 1997, 8 cases occurred in November and 1 case occurred in December. In 1998, 13 cases occurred in November and 2 cases occurred in December. In 1999, 1 case occurred in May, 28 cases in November, and 6 cases in December.
All these patients were examined for serum antibody (1) and for the O. tsutsugamushi genome whenever the blood from patients in the disease's the acute phase was available (2). The serum antibody was detected using the immunofluorescent technique employing antigens of Gilliam, Karp, Kato, Kawasaki, and Kuroki types (1). Sera showing more than a 4-fold increase of IgM or IgG titers in the disease's convalescent phase in comparison with the acute phase or those showing IgM titers exceeding x80 in the acute phase were considered positive. The O. tsutsugamushi genome was detected using nested PCR using genus Orientia-specific primers and type-specific primers (3, 4).
A portion of the data for individual patients is reproduced in Table 1. Sera #98038, #98044, #98045, and #98046 reacted with all of the antigens of Gilliam, Karp, Kato, Kawasaki, and Kuroki, but, with PCR using type-specific primers, the first and the last specimens were positive for only the Kuroki type, while the second and third were positive for only the Kawasaki type. Sera PCR-positive for the Kawasaki type tended to show higher antibody titers for both Gilliam and Kawasaki types (#98043, #98044, and #98045). This is probably because the 56 kDa proteins of the both types shared a common epitope (5). However, some sera (ex., #99033) were positive for only antibody against the Kawasaki type. Use of all the five type anigens, i.e., the Kawasaki and Kuroki type antigens in addition to the three standard antigens, Gilliam, Karp and Kato type antigens, is recommended to increase the sensitivity of antibody detection.
Acute phase sera were generally positive for the genome in PCR. However, some sera, such as #98047, which attained high antibody levels already in the acute phase were negative for the genome.
Table 2 summarizes immunological and PCR data. About 80% of
the cases were due to the Kawasaki type, a tendency which is in
agreement with the data obtained in Miyazaki (1) and Chiba Prefectures
(6). But 3 cases (6.4%) were untypable; this may be due to mutations
which made the genome detection impossible using the five sets
of primers used.
The work was supported by a grant-in-aid by the Ministry of Health
and Welfare of Japan.
REFERENCES
*Corresponding author: Fax: +81-45-363-1037
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