Jpn. J. Infect. Dis., 53, 2000

Laboratory and Epidemiology Connumications
Japanese Spotted Fever Cases in Kochi Prefecture
Seizo Chiya*, Nobu Tahhashi, Tomihisa Yasuoka, Teruko Komatsuand Hideyoshi Suzuki
The Public Health Institute ofKochL'Prefecture,
Marunouchi 2‑411, Kochi‑shi, Kochi 780‑0850, Japan
Communicated by Hiroo Inouye(Accepted March 30, 2000)

accountinthe differential diagnosis ofrickettsiosis occurlng
in Kochi Prefecture from spnng to summer. The seasonal

Jap甲ese苧potted fever (JSF) is caused by tick‑bone Rick‑ettsL.aJaPOnlCa･ It was flrSt discovered by Dr. F. Maharain
Tokushima Prefecturein1984 (1). Sincethen, as of 1998, ten

fluctuation of ticks (imago, larva) which mediate JSF wasprefecturesincluding Kochi Prefecture (2)and Miyazaki

observedinMtwoto City. Its occurrence was much higherthan

Prefecture (3) have reported JSF cases tothe National Instituteof Infectious Diseases, Japan(NIID).

the peak or the number of ticks collected and that of JSF

inthearea where JSF cases are not reported (4). However,h Kochi Prefecture, 94 JSF cases were conflrmedin1983‑
1999; 86inMuroto City, 1 caseinKitagawa Village, 4 cases
inKochi City,and 3 casesinSukumo Village. Among the 4cases reported from Kochi City, 3 wereknown to beinfectedin Muroto City. Thus, JSF is as if an endemic disease inMuroto City.
During the same period, only 9 cases of scrubtyphus

cases were differentinregard to timing. JSF infection isprobably affected by many factors, such as the habits of ticks
and their hosts, whichare mutuallyinterwoven.

Sixtypercent of JSF patients were females. The age rangeof patients was widely spread &om age 3 to 96･So far, half of the JSF patients reportedinKochi Prefectuqe

did not show bites, one of the three typical symptoms ofJSF.

(caused by Chigger‑bone Orientia (formerly Rickettsia) tsu‑tsugamushi) were reported; 7 cases in the Reihoku Area

Irrespective of the presence of bites, in Muroto Citywhere
the patients were most numerous, diagnosis was madewithin(Ohtoyo Town, Motoyama Town,and Tosa Town), I casein
Kochi City,and 1 case in Touwa Village (Fig. 1, 2). JSF
infections were more &equentinthe agicultural fields, plains,and mountains along the seacoast, while scrubtyphusinfec‑tions were morefrequentintheinland mountainousareas.

3 to 5 days after disease onset. However,inKochi Citywhere
JSF was relatively rare, two of fourJSF patients without bites
had to wait longer than 10 days for definitive diagnosis in

spite of the continuous presence of high fever. If presence ofbites is over‑emphasized in diagnosis, there is a risk ofh Kochi Prefecture, JSFinfection is frequent between April

belated diagnosis. Ignorance oftherisk ofJSFamOng medical
institutions may also cause belated diagnosis.
Our researchindicatedthe presence of otherareas showingand November, while scrubtyphus breaks outinOctoberandNovember (Fig･ 3). Thus, JSF has always to be taken intoa highprevalence of antibody‑positive populationinKochi
Prefecture (5). In suchareas, JSF infection could be high*Co汀eSpOnding author: Fax +81‑88‑872‑6324, E‑mail: seizou

thoughumoticed. Therefore, Preparedness for quick diagnosis

̲ch iya@ken2. pref. kochi.j p27

Jpn. J. Infect. Dis., 53, 2000
田Japanese spotted fever D Scrub typhus

Cases 1614121086420838485868788899091 9293949596979899Year

Fig. 1. Yearly cases of Japanese spotted fever in Kochi Prefecture; compaq.isonwiththat ofscrubtyphus (198311999)

Re払ohl, 7Fig. 2. Cases ofrickettsial disease in Kochi Prefecture

園Japanese spotted fever

C a SeS□ Scrub typhus

2 1 1 1 1 1 0 8 QE) 4 クー0 8 6 4 2 04567891011MotLthFig･ 3･ Incidence of Japanese spotted fever in Kochi Prefecture by mondI; COmparisonwiththat of scrub typhus (1983‑1999)

in suchareas is necessary. Knowledge of JSF should be

Department of Tokushima Universityin1983‑ 1995and has

distributed throughoutthe prefecture.

been performed by us since 1 995. The conflrmatOry examina‑tion we used was thefluorescentantibody method uslng R.

Thoughtheareas of reported JSFinfectionare expanding,its main focus will continue to be Muroto City. It is warmall

japonica YH strain (distributed by NIID)and Tauchi strain

yeararound owlng tOthe Kuroshio Current,and it is a fertile

isolated in our institute as antigens.

aqea forthe grow血of血itsand vegetables･ Thearea provides

a suitable environment for small animals which may carry

REFERENCE S

various kinds of ticks which seek chances to suckthe bloodofhumanSand smallanimalsinfieldsand mountains. More‑over, according to our research (6), citizens of Muroto City

1. Mahara, F., Koga, K., Sawada, S., Taniguti, T., Sigeml,

are Ignorant Oftherisk. This fact may accelerate the endemic

T. and Uchida, T.(1985): The血st report oftherickettsialofJSF.

infection of spotted fever groupinJapan; three clinicalF., Suto, K., Tsuboi, Y., Ooya, A., Koyama, H., Uchiyama,cases. J. Jpn.Assoc. Infect. Dis., 59, I 16511 172 (inJapa‑A serologlCal survey was performed by the Virology

28Jpn. J. Infect. Dis., 53, 2000

tick‑Lbome diseases from ticksinMuroto Cityof Kochinese).

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fever group in Muroto City. Rep. Public Health Kochi,
43, 43‑51 (inJapanese).
6. Chiya, S., Takahashi, N., Ideguchi, S., Suzuki, H. andTsuboi, Y.( 1 995): Prevalence of antibodies torickettsiosis
ofspotted fever groupinKochi. Rep. Public HealthKochi,

75‑78.

4l Chiya, S･, Takahashi, N., Yasuoka, T., Ideguchi, S. andSuzuki, H.(1998): Survey of tick faunaand rickettsia of41, 27‑31 (inJapanese).

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