Vol.32
No.02
JUNE 2004

Tropical Medicine and Health

Tropical Medicine
and Health

ISSN 1348-8945

Vol.32 No.02 JUNE 2004

ISSN 1348-8945【CONTENTS】
Original article
Changes in HTLV-I positive rates among pregnant women in Okinawa prior to the effectsof measures introduced to prevent vertical transmission through breast milk feeding
Ando, Y., Matsumoto, Y., Nakano, S., Saito, K., Kakimoto, K., Tanigawa, T.,
Ekuni, Y., Kawa, M., Toyama, Y., and Toyama, T.

177

Inhibition of Trypanosoma cruzi growth in mammalian cells by nimodipine,with low
cytotoxicity to host cells
Hirota, K., Tsubouchi, A., Nakajima-Shimada, J., Nara, T., and Aoki, T.

181

A list of and keys to black flies (Diptera:Simuliidae) in Thailand
Takaoka, H. and Choochote, W.

189

The use of travel vaccines by Japanese expatriates in developing countries
Hamada, A., Ujita, Y., Okuzawa, E., Koga, T., Uchikoshi, A., Fukushima, S., Hondo, K.,
Nichikawa, T., and Basugi, N.

199

Vol.32 No.02 JUNE 2004

Tropical Medicine
and Health

Short Communication
Detection rates of rotavirus antigen from diarrheal patients in Lao people’s democratic republic
Phantouamath, B., Sithivong, N., Sisavath, L., Mounnalath, K.,
Chomlasak, K., Insisiengmay, S., Yamashiro, T., and Iwanaga, M.
203
Proceedings of the 44th Annual Meeting of Japanese Society of Tropical Medicine andthe 18th Annual Meeting of Japan Association for International HealthSymposium 3: Clinical Approach of Tropical Infectious Diseases (in Japanese)

205

JAPANESE SOCIETY OF TROPICAL MEDICINEJAPANESE SOCIETY OF
TROPICAL MEDICINE

Trop.Med.Health日本熱帯医学会表紙!−" ＣＭＹＫ 稲 芦塚 宮副

背は３mm
（決）

Vol.32
No.02
JUNE 2004

Tropical Medicine and Health

Tropical Medicine
and Health

ISSN 1348-8945

Vol.32 No.02 JUNE 2004

ISSN 1348-8945【CONTENTS】
Original article
Changes in HTLV-I positive rates among pregnant women in Okinawa prior to the effectsof measures introduced to prevent vertical transmission through breast milk feeding
Ando, Y., Matsumoto, Y., Nakano, S., Saito, K., Kakimoto, K., Tanigawa, T.,
Ekuni, Y., Kawa, M., Toyama, Y., and Toyama, T.

177

Inhibition of Trypanosoma cruzi growth in mammalian cells by nimodipine,with low
cytotoxicity to host cells
Hirota, K., Tsubouchi, A., Nakajima-Shimada, J., Nara, T., and Aoki, T.

181

A list of and keys to black flies (Diptera:Simuliidae) in Thailand
Takaoka, H. and Choochote, W.

189

The use of travel vaccines by Japanese expatriates in developing countries
Hamada, A., Ujita, Y., Okuzawa, E., Koga, T., Uchikoshi, A., Fukushima, S., Hondo, K.,
Nichikawa, T., and Basugi, N.

199

Vol.32 No.02 JUNE 2004

Tropical Medicine
and Health

Short Communication
Detection rates of rotavirus antigen from diarrheal patients in Lao people’s democratic republic
Phantouamath, B., Sithivong, N., Sisavath, L., Mounnalath, K.,
Chomlasak, K., Insisiengmay, S., Yamashiro, T., and Iwanaga, M.
203
Proceedings of the 44th Annual Meeting of Japanese Society of Tropical Medicine andthe 18th Annual Meeting of Japan Association for International HealthSymposium 3: Clinical Approach of Tropical Infectious Diseases (in Japanese)

205

JAPANESE SOCIETY OF TROPICAL MEDICINEJAPANESE SOCIETY OF
TROPICAL MEDICINE

Trop.Med.Health日本熱帯医学会表紙!−" ＣＭＹＫ 稲 芦塚 宮副

背は３mm
（決）

Tropical Medicine and Health Vol. 32 No. 2, 2004, pp. 177-180
Copyright! 2004 by The Japanese Society of Tropical Medicine

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CHANGES IN HTLV-I POSITIVE RATES AMONG PREGNANT WOMEN IN
OKINAWA PRIOR TO THE EFFECTS OF MEASURES INTRODUCED TO
PREVENT VERTICAL TRANSMISSION THROUGH BREAST MILK FEEDINGYOSHIYA ANDO１＊, YOSHINARI MATSUMOTO１, SHIRO NAKANO２, KENSUKE SAITO３,
KAZUHIRO KAKIMOTO４, TAKUO TANIGAWA５, YUTAKA EKUNI６,
MOTOHIRO KAWA７, YUJI TOYAMA８, TAKENORI TOYAMA８
Accepted 28, April, 2004

Abstract: Objectives: Human T cell leukemia virus type-I (HTLV-I) is a causative agent of human T-cell leukemia
and HTLV-I associated myelopathy (HAM/TSP). HTLV-I carriers are often infected vertically, especially via
mother’s milk. Since 1985, clinical measures have been adopted at a hospital in Okinawa to prevent vertical infections.
Methods: We examined HTLV-I antibodies in all of the women (total 11,506) who gave birth after 24 gestational
weeks at a hospital on the Okinawa main island from January 1985 to December 1999.
Results: The positive rate among all pregnant women was always higher than that among primipara alone. Both figures decreased over the period studied, but the primiparity rate (36-39%) did not change significantly. The percentage of HTLV-I positive primipara pregnant women among the HTLV-I positive total was close to the primiparity
rate from 1985 to 1988, but it was considerably lower than the overall primiparity rate thereafter (22-26%).
Conclusions: Preventive measures against HTLV-I infection did not contribute to the decrease in HTLV-I positive
mothers before 1999 because these measures were adopted from 1985, and so there must be other reasons for thedecrease in HTLV-I positive rate. Further studies on social factors and by year of birth are needed to identify factors
influencing HTLV-carrier ratios among pregnant women.
Key words: HTLV-I, Okinawa, pregnancy, ATL

INTRODUCTION
Adult T cell leukemia (ATL), which develops in human T cell leukemia virus I (HTLV-I) carriers [1], is endemic in several regions of the world, including southwestern Japan [2,3]. Routes of infection are vertical, the mainone, and horizontal [4]. Because there is no possibility ofdeveloping ATL after horizontal infection of HTLV-I by
１sexual intercourse, one of the best ways to reduce the morbidity rate of ATL is to prevent vertical infection.
Vertical infection is transmitted primarily via mother’s
milk [5,6]. Thus, to prevent HTLV-I infection via this route,freeze-thawing mother’s breast milk and other measures forbreast milk feeding have been instituted [7,8]. It is known
that these methods can prevent mother-infant infection, but
it is still too early to draw a conclusion if these preventive

Wakayama Medical University, Kihoku Hospital, Obstetrics and Gynecology, Myoji 219, Katsuragi, Ito, Wakayama 649-7113, Japan
Saiseikai Nara Hospital
Hachijo-cho 4-634, Nara, Nara 630-8146, Japan
３
Saiseikai Tondabayashi Hospital
Kouyou-dai 1-3-36, Tondabayashi, Osaka 584-0082, Japan
４
International Medical Center of Japan
Toyama 1-21-1, Sinjuku, Tokyo 162-8655, Japan
５
Daido Life Insurance Company
Edobori 1-2-1, Nishi, Osaka, Osaka 550-0002, Japan
６
Ekuni Ladies Clinic
Seika-dai 3-12-2, Seika, Sohraku, Kyoto 619-0238, Japan
７
Nara Prefectural Nara Hospital
Hiramatsu 1-3-3, Nara, Nara 631-0846, Japan
８
Toyama Obstetrical Gynecological Clinic
Ohjana 5-20-8, Ginowan, Okinawa 901-2225, Japan＊
Correspondence to: Yoshiya Ando, MD
Wakayama Medical University, Kihoku Hospital, Obstetrics and Gynecology, Myoji 219, Katsuragi, Ito, Wakayama 649-7113, Japan
Tel/Fax: +81-736-22-8250 E-mail: yando@wakayama-med.ac.jp
２

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measures have contributed to a decrease in the carrier rates
in areas that instituted these measures.
The above measures have been applied clinically at a
hospital in Okinawa since 1985. Hospital records showedthat the youngest pregnant woman during the period of thisstudy, 1985-1999, was born in 1983. Hence, none of thepregnant women were affected by the preventive measures.
An examination of the changes in HTLV-I carrier rates from1985 to 1999 will help to shed light on the impact of theclinical preventive effects of the feeding of freeze-thawed
mother’s breast milk and other measures, because the effects of these measures would have become apparent after
2000 when a baby born in 1985 became 15 years old. Thus
we examined HTLV-I antibodies in all of the pregnant
women who since 1985 gave birth at over 24 gestational
weeks at a hospital on the main island of Okinawa in southwestern Japan, and we obtained interesting findings.

MATERIALS AND METHODS
Location and Population
Subjects were patients at the Toyama Obstetrical Gynecological Clinic in Ginowan City on the Okinawa mainisland in southwestern Japan (Fig 1). From April1 985 toMarch 2000, a total of 29,385 babies were born in this city,and from January1985to December 1999, a total of 11,506
pregnant women gave birth at over 24 gestational weeks at
the hospital from which the data was collected.
Assay of serum antibodies to HTLV-I

positive by PA were confirmed by the immuno-fluorescencemethod using HTLV-I infected cell line MT-1 [9] originatedby Hinuma et al. [10] All HTLV-I positive pregnant women
were informed of the result, and before delivery they wereadvised to institute feeding by artificial milk or freezethawing of mother’s milk to their newborns.

RESULTS
From January 1985 to December 1999, a total of
11,506 pregnant women (4,259 primiparas) gave birth at a
gestational age of over 24 weeks at our hospital. Patientcharacteristics are shown in Table I. The average age ofprimipara pregnant women was 25.9±4.6, and that of all
pregnant women was 28.6±5.0. The HTLV-I positive rate
among all the pregnant women and among the primipara
pregnant women alone was studied (Figure II). Though bothrates became lower over the term of the study, the positive
rate among all pregnant women was always higher than thatamong primipara pregnant women.
Table II shows the analysis of HTLV-I positive rates bybirth years. The positive rate gradually decreased by birthyear, especially in primipara pregnant women.
Figure III shows the changes in the overall primiparity

Figure 2. HTLV-I positive rate among all pregnant women andprimipara pregnant women who delivered at over 24
gestational weeks. ●, total pregnant women, ○,primipara pregnant women. (numbers of positive
women / all women)

Figure 1. The location of Ginowan City on the Okinawa mainisland in southwestern Japan.

For particle agglutination (PA) assay and screening of
HTLV-I, peripheral blood was drawn from all pregnant
women after obtaining informed consent, and the results
were judged as either positive or negative. Samples judged

Figure 3. Primipara rate among the total of all pregnant
women (■) and primipara HTLV-I positive pregnant rate among the total of all HTLV-I positive
pregnant women (◇).

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Table!. Characteristics of pregnant women.
years
Primipara
MultiparaNo.
Age±SDNo.
Age±SD

1985〜1987
1081
26.23±4.562996
30.11±4.66

1988〜1990
895
25.84±4.562487
30.11±4.67

1991〜1993891
25.75±4.512355
30.11±4.68

1994〜1996
759
25.73±4.562025
30.11±4.69

1997〜1999
633
26.11±4.69
1643
30.11±4.70

All women delivered at over 24 gestational weeks from January 1985 to December 1999

Table". HTLV-I positive rate among pregnant women by year of birth.
birth years% of positive
Primipara
positive/total% of positive
Multipara
positive/total

〜1954
4.81
9/187
5.30
55/1037

1955〜1959 1960〜1964 1965〜1969 1970〜1974
4.32
3.45
2.57
1.40
24/555
40/1159
32/1246
11/785
5.34
4.18
2.67
1.23
3/104
3/105
3/106
3/107

rate and the HTLV-I positive primiparity rate. The primiparity rate tended to increase slightly within a range of 36.138.5%. The primiparity rate of HTLV-I positive pregnant
women was close to the overall primiparity rate from 1985
to 1988, and then stabilized within 25.8-22.4%, considerably lower than the primiparity rate, thereafter.

DISCUSSION
We reported the world’s first preventive measureagainst HTLV-I, i.e. feeding by freeze-thawing of mother’smilk, and this measure and other prevention measures havebeen adopted in Okinawa Prefecture since 1985 [8]. Now,
the preventive measures are evaluated [11,12], but that thechanges in HTLV-I positive rates among pregnant women
who were born before 1985 were not affected the preventive
measures for mother-infant infection.
In the present study, we examined the changes in
HTLV-I positive rate among pregnant women from 1985 to
1999. The positive rate among all pregnant women is clinically, but, since the same mother might deliver more thanonce at the same hospital, primipara pregnant women werealso examined to avoid any overlapping of positive individuals.
The positive rate among primipara pregnant womenand among all pregnant women decreased over time. The
positive rate among primipara pregnant women decreased
dramatically between 1985 and 1993, while the total positive rate began to fall rapidly about 3 years later, over theperiod from 1988 to 1993.
The preventive measures against HTLV-I infection, i.e.
modified milk feeding and feeding by freeze-thawing of
mother’s breast milk, did not contribute to the decrease in
the HTLV-I positive rate among mothers who delivered before 1999 because these measures have been adopted only
since 1985. However, it is possible that the studies actually

1975〜
0.32
1/312
2.78
3/108

affected the number of children born from women who
were HTLV-I positive, because women whose first childwas HTLV-I positive may have decided to avoid delivering
another child so as not to worry about further HTLV-I infection. Hence, we looked for changes in the primiparity rateand its correlation with the percentage of primipara pregnant women among all HTLV-I positive pregnant women.
The percentage of primipara women among all HTLVI positive pregnant women was close to the primiparity ratefrom 1985 to 1988 but was considerably lower than theprimiparity rate thereafter (22-26%), indicating a difference
between the pregnant women who delivered around 1988
and thereafter and those who delivered prior to this date.
The cohort effect does not significantly influence the decrease in positive rate, because if HTLV-I positive women
avoid delivering a second child, the primiparity rate should
increase year by year, and the percentage of primipara pregnant women among the HTLV-I positive pregnant womenshould also increase remarkably. However, there are many
possible reasons for a spontaneous decrease in the positiverate.
Kashiwagi K. et al. [13] pointed to a decrease in thenumber of mothers breast feeding and a shortening of thebreast-feeding period.
Socioeconomic changes in Okinawa and the improvement of the health environment can also be sited as reasonsfor decrease in HTLV-I positive rate among pregnant
women.
The aim of this study was to ascertain the changes in
HTLV-I positive rates among pregnant women in Okinawa
prior to any effects of the introduction of measures to prevent vertical transmission through breast milk feeding. We
found a decrease in HTLV-I positive rates among pregnant
women. In the further, we intend to evaluate the effects ofthe measures introduced to prevent vertical transmission
through breast milk feeding in light of the results shown in１
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this study. Further studies regarding social factors, and rates
by the year of birth, are needed to identify factors influencing HTLV-carrier rates among pregnant women.

ACKNOWLEDGMENTS
We are deeply grateful to the Statistic Division of Ginowan City Office, Okinawa, and the staff of the Toyama
Obstetrical and Gynecological Clinic for their help.

REFERENCES
１）Uchiyama T, Yodoi J, Sagawa K, Takatsuki K, Uchino H.
Adult T-cell leukemia: clinical and hematologic featuresof 16 cases. Blood 1977;50:481-492.
２）Hinuma Y, Komoda H, Chosa T, Kondo T, Kohakura M,
Takenaka T, Kikuchi M, Ichimaru M, Yunoki K, Sato I,
Matsuo R, Takiuchi Y, Uchino H, Hanaoka M. Antibodies
to adult T-cell leukemia-virus-associated antigen (ATLA)in sera from patients with ATL and controls in Japan: anation-wide sero-epidemiologic study. Int J Cancer 1982;
15:631-635.
３）Hino S, Katamine S, Miyata H, Tsuji Y, Yamabe T, Miyamoto T. Primary prevention of HTLV-1in Japan. Leukemia 1997; 11Supp l3: 57-59.
４）Okochi K, Sato H, Hinuma Y. A retrospective study ontransmission of adult T cell leukemia virus by bloodtransfusion: seroconversion in recipients. Vox Sang 1984;
46:245-253.
５）Kinoshita K, Yamanouchi K, Ikeda S, Momita S, Amagasaki T, Soda H, Ichimaru M, Moriuchi R, Katamine S,
Miyamoto T. Oral infection of a common marmoset withhuman T-cell leukemia virus type-I (HTLV-I) by inoculating fresh human milk of HTLV-I carrier mothers. Jpn J
Cancer Res 1985;76:1147-1153.

６）Nakano S, Ando Y, Saito K, Moriyama I, Ichijo M,
Toyama T, Sugamura K, Imai J, Hinuma Y. Primary infection of Japanese infants with adult T-cell leukaemiaassociated retrovirus (ATLV): evidence for viral transmission from mothers to children. J Infect 1986;12:205-212.
７）Ando Y, Kakimoto K, Tanigawa T, Furuki K, Saito K,
Nakano S, Hashimoto H, Moriyama I, Ichijo M, Toyama
T. Effect of freeze-thawing breast milk on vertical HTLVI transmission from seropositive mothers to children. Jpn
J Cancer Res 1989;80:405-407.
８）Ando Y, Saito K, Nakano S, Kakimoto K, Furuki K, Tanigawa T, Hashimoto H, Moriyama I, Ichijo M, Toyama T.
Bottle-feeding can prevent transmission of HTLV-I frommothers to their babies. J Infect 1989;19:25-29.
９）Miyoshi I, Miyamoto K, Sumida M, Nishihara R, Lai M,
Yoshimoto S, Sato J, Kimura I. Chromosome 14q+ in
adult T-cell leukemia. Cancer Genet Cytogenet 1981;3:
251-259.
１０）Hinuma Y, Nagata K, Hanaoka M, Nakai M, Matsumoto
T, Kinoshita KI, Shirakawa S, Miyoshi I. Adult T-cellleukemia: antigen in an ATL cell line and detection of antibodies to the antigen in human sera. Proc Natl Acad Sci
1981;78:6476-6480.
１１）Ando Y, Matsumoto Y, Nakano S, Saito K, Kakimoto K,
Tanigawa T, Ekuni Y, Kawa M, Toyama T. Long-term follow up study of vertical HTLV-I infection in bottle-fed
children born to seropositive mothers. J Infect 2003;46:911.
１２）The Tsushima ATL Study Group. Short-term breastfeeding may reduce the risk of vertical transmission of
HTLV-I. Leukemia 1997;11Suppl3:60-62.
１３）Kashiwagi K, Furusyo N, Nakashima H, Kubo N,
Kinukawa N, Kashiwagi S, Hayashi J. A decrease inmother-to -child transmitsion of human T lymphotropic
virus type I (HTLV-I) in Okinawa, Japan. Am J Trop Med
Hyg 2004;70:158-163.

Tropical Medicine and Health Vol. 32 No. 2, 2004, pp. 181-188
Copyright! 2004 by The Japanese Society of Tropical Medicine

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INHIBITION OF TRYPANOSOMA CRUZI GROWTH
IN MAMMALIAN CELLS BY NIMODIPINE,
WITH LOW CYTOTOXICITY TO HOST CELLSKENICHIRO HIROTA, AKIKO TSUBOUCHI, JUNKO NAKAJIMA-SHIMADA,
TAKESHI NARA and TAKASHI AOKI＊
Accepted 30, April, 2004

ABSTRACT: An in vitro infection system of Trypanosoma cruzi and HeLa cells was used to measure the anti-T.
cruzi activities of various calcium antagonists classified into dihydropyridines, diphenylalkylamines, and benzothiazepines and of allopurinol and benznidazole as medium and highly effective reference compounds, respectively.
Six dihydropyridines (10 µM each), i.e. nifedipine, nicardipine, nimodipine, nisoldipine, nitrendipine, and amlodipine, decreased the rates of infection of HeLa cells from 11.7% (control) to 5.8, 0.9, 1.2, 3.6, 5.9, and 1.7%, respectively. Nicardipine and amlodipine were highly toxic to HeLa cells, causing detachment of cells from coverslips. Nimodipine was thus the most effective inhibitor tested against T. cruzi infection in HeLa cells. Verapamiland gallopamil (diphenylalkylamines), diltiazem and midazolam (benzothiazepines), and allopurinol (positive control) were less effective than nimodipine. IC５０ values, the concentrations of compounds that elicited a 50% reduction in the infection rates of HeLa cells, were 2.5, 2.6, 1.3, 2.1, and 1.7 µM for nicardipine, nimodipine, amlodipine, verapamil, and benznidazole, respectively, while the values for nifedipine, diltiazem, and allopurinol weremuch higher. Nicardipine, amlodipine, and verapamil again showed significant cytotoxicities to HeLa cells. When
Swiss 3T3 fibroblasts replaced HeLa cells, nimodipine markedly lowered the host-cell-infection rate, with an IC５０
value of 8.3 nM. Thus, nimodipine is expected to be a highly effective anti-T. cruzi lead compound, with low cytotoxicity to mammalian cells. Structural formulas of nimodipine and nicardipine in relation to their low and high cytotoxicities, respectively, against HeLa cells are discussed.
Key Words: Trypanosoma cruzi, calcium antagonist, nimodipine, dihydropyridine, growth inhibition

INTRODUCTION
Chagas’ disease, the causative agent of which is a parasitic protozoan Trypanosoma cruzi, affects about 17 million
people, and 25% of the population of Latin America is at
risk of acquiring this protozoan infection [1]. T. cruzi exhibits two different pathogenic forms in mammalian hosts[2,3]. The nondividing and infective trypomastigote form,
which possesses a flagellum, circulates in the bloodstream.
After invasion into host cells, the trypomastigote form
transforms into the amastigote form, which has no free flagellum. The amastigote multiplies by binary fission in thehost cell cytoplasm and eventually transforms back to thetrypomastigotes, resulting in the breakdown of infected
cells and re-emergence in the circulation.
Nifurtimox and benznidazole are currently used forchemotherapy of Chagas’ disease [1], but these drugs arehighly toxic, often leading to the discontinuation of thetherapy. An effective therapeutic agent with a low toxicity isthus needed. To this end, we previously established a culture system of the host HeLa cells infected with T. cruzi and,using this system, determined quantitatively the timecourses of the protozoan infection and proliferation [4,5].
This in vitro system also enabled us to examine purine andpyrimidine analogs, including allopurinol, for their efficacies in inhibiting the rate of host cell infection by T. cruzi
and the parasite growth inside the host cells [4].
Invasion into mammalian cells by T. cruzi requires theactivation of signaling pathways and Ca２＋ response both in
the parasite and in the host cell [6,7]. Application of thisknowledge to chemotherapy against experimental murine
Chagas’ disease resulted in the amelioration of the acuteand chronic stages of T. cruzi infection by verapamil, a Ca２＋
antagonist of the diphenylalkylamine class [8,9], with no effect on the protozoan calcium homeostasis by nifedipine[10], another Ca２＋ antagonist of the dihydropyridine class.

Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan＊
Corresponding author: Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku,
Tokyo 113-8421, Japan. Tel:+81-3-5802-1042, Fax:+81-3-5800-0476. E-mail address: tksaoki@med.juntendo.ac.jp

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We report here that the in vitro HeLa and T. cruzi infection
system is also useful for examination of various Ca２＋ antagonists for anti-T. cruzi activities, and that nimodipine, asecond generation calcium antagonist of the dihydropyridine class, markedly reduced the parasite infection and proliferation in mammalian cells, with lower cytotoxicity
against the host cells. The effects of these (nifedipine-like)
dihydropyridines on parasite infection and proliferation inother mammalian cells, i.e. fibrosarcoma HT 1080 and
Swiss 3T3 fibroblasts, were also examined in this study.

MATERIALS AND METHODSMedia and chemicals
Eagle’s Minimum Essential Medium (MEM) and Dulbecco Modified Eagle’s Medium (DMEM) were obtained
from Sigma-Aldrich Japan. Fetal bovine serum (FBS) was
obtained from Daiichi Pure Chemicals, Tokyo, Japan. DiffQuick and HSR solutions (International Reagents Corp.,
Kobe, Japan) were used for staining cells infected with T.
cruzi and for embedding the stained specimens, respectively. The following Ca２＋ antagonists were obtained from
Wako Pure Chemical Industries, Tokyo: nifedipine,
nicardipine hydrochloride, nisoldipine, nitrendipine, amlodipine besilate, gallopamil hydrochloride, and diltiazem
hydrochloride. Other Ca２＋ antagonists, i.e. nimodipine andverapamil hydrochloride (Sigma-Aldrich) and midazolam(F. Hoffmann-La Roche, Basel, Switzerland), were also
used. Allopurinol was obtained from Sigma-Aldrich andbenznidazole was kindly provided by F. Hoffmann-La
Roche. These compounds were dissolved in 50% ethanol
prior to the examination for anti-T. cruzi activity; the solvent, the final concentration of which was adjusted to 1.0%,
did not significantly affect the protozoan infection in HeLa
cells. Other chemicals were commercial products of thehighest grade.
Parasite and mammalian cells
The Tulahuen strain of Trypanosoma cruzi and HeLa
cells, used as an in vitro host, were maintained and passaged in cultures as described previously [4,5]. Briefly, thehuman cancer cell line, HeLa, and the infection complex of
the HeLa cells and T. cruzi [11]were successively subcultured every 3 to 4 days at cell densities of 3-5 x 10５HeLa
cells per ml (total volume of 5 ml) in 25-cm２ plastic flasks.
Swiss 3T3 fibroblasts were provided by F. Hanaoka, Graduate School of Frontier Biosciences, Osaka University. This
cell line was subcultured every 3 days at an initial cell density of 3 x 10５ per ml (total volume of 5 ml) in DMEM containing 10% FBS in 25-cm２ plastic flasks [4]. HT 1080 cells,
a human fibrosarcoma cell line, were obtained from the Ja-

pan Health Sciences Foundation (Tokyo, Japan) and subcultured as in the case of Swiss 3T3 cells [12]. Throughout thepresent study, cell cultures were maintained in a humidified
incubator at 37°
C and at 5% CO２ in air.
In vitro infection and addition of test compounds
HeLa cells were infected in vitro with T. cruzi trypomastigotes using a modification of the method described
previously [4,5]. A round coverslip (12 mm) was placed ineach well of the 24-well plate. Into these wells were added
the logarithmically growing HeLa cells (5 x 10３/ml/well),harvested from the preceding subcultures. After incubation
at 37°C for 2 days, the cells were infected with T. cruzi trypomastigotes (3 x 10６ parasites/well) as described previously [4]. Within 24 hours after the infection the parasite invasion appeared to be accomplished. The trypomastigotes
remaining in the medium were not removed in this study.
Each chemical compound tested for its inhibitory effect on the parasite infection and proliferation was added
immediately after the infection and was left in the medium
during the experiment. Similarly, Swiss 3T3 and HT 1080
cells were also infected with T. cruzi and examined effectsof the added compounds. Cytotoxicities caused by test compounds against normal control host cells were estimated on
the basis of the decrease in cell number per microscopic image (54 µm x 112 µm), using the above system of host cells+T. cruzi+test compound with an omission of T. cruzi infection.
Determination of the rate of host-cell infection and parasiteproliferation
The method for determining the rate of infection by T.
cruzi of host cells was described in detail [4]. Briefly, hostcells attached onto the coverslip were fixed and stained with
Diff-Quick in the well of a 24-well plate, then the coverslip
was transferred upside down onto a slide glass, and the cells
were finally embedded in the HSR solution for observation
under a light microscope. The microscopic images of 54µm x 112 µm (see Fig. 3), taken by a conventional digital
camera, were used for counting the number of total cells,
infected cells, and amastigotes per image. The percentage of
infected host cells containing more than one amastigote andthe mean number of amastigotes per infected cell were determined by analyzing more than 200 host cells distributedin four randomly chosen microscopic fields. The results
were statistically evaluated by the t test for small samples.
Differences between means giving a probability of less than
5% were considered significant.

１
８
３

RESULTSTime course of effects of nimodipine on the rate of infectionof HeLa cells and on the average number of amastigotes
per infected HeLa cell
In a preliminary examination, nimodipine, a second

Figure 1. Time course of effects of nimodipine on the rate of
Trypanosoma cruzi infection of HeLa cells and on
the average number of amastigotes per infected
cell. Exponentially growing HeLa cells (5 x 10３/well) were inoculated in each well of 24-wellplates, cultured for 2 days, and infected with 3 x
10６ trypomastigotes of the T. cruzi Tulahuen strain.
Immediately after the infection, 10 µM nimodipine, allopurinol or benznidazole was added.
The host-cell-infection rate (A) and the average
amastigote number per infected cell (B) were determined every 24 hours as described in Materials
and Methods. Closed circle, control (no compound added); open circle, 10 µM allopurinol;
closed triangle, 10 µM nimodipine; open triangle,
10 µM benznidazole. Data shown are the means±
1 SD of 3 separate determinations.

generation calcium antagonist of the dihydropyridine class,markedly decreased the T. cruzi infection and proliferationin HeLa cells in vitro (data not shown). Accordingly, we determined the effect of this compound on the time course of
the host-cell-infection rate and the average parasite (amastigote) number per infected HeLa cell, using allopurinol andbenznidazole as a medium and a highly effective referencecompound, respectively (Fig. 1). In the control wells withno added compound and with 1.0% ethanol as the solvent
control, the infection rate (Fig. 1A) and the average amastigote number (Fig. 1B) were increased time-dependently
by day 5 and day 6, respectively. Addition of allopurinol resulted in gradual increases, although generally to a lesser
extent than the control, in the infection rate and the amastigote number by day 6 and day 7, respectively. Nimodipine
did not appear to significantly lower the rate of T. cruzi infection of HeLa cells by day 2, with the decreased average
number of amastigotes per infected HeLa cell. Subsequently, however, particularly on day 4, we clearly observed
the differences in the rate of host cell infection among thecontrol, allopurinol-, nimodipine- and benznidazole-added
wells (Fig. 1A). Benznidazole, a drug currently used fortreatment of Chagas’ disease in Latin America, appeared tobe the strongest inhibitor for the infection rate of HeLa cells
and the average amastigote number per infected cell. Technically, the infection rate and the parasite number on day 1
and 2 were sometimes variable, while on day 6 the infected
HeLa cells were often detached from the coverslips during
the staining procedure. Unless otherwise stated, therefore,
the infection rate and the parasite growth were determinedon day 4 after the T. cruzi infection and the addition of test
compounds.
Effects of various Ca２＋ antagonists on the rate of infectionof HeLa cells and on the average number of amastigotes
per infected HeLa cell
Figures 2A and 2B show the effects of various calcium
antagonists on the rate of infection of HeLa cells and on the
average number of amastigotes per infected cell, respectively. Nifedipine, nicardipine, nimodipine, nisoldipine,
nitrendipine, and amlodipine markedly lowered the infection rate from 11.7% (control) to 5.8, 0.9, 1.2, 3.6, 5.9, and
1.7%, respectively. Decreases in the average amastigote
number per infected HeLa cell, elicited by these dihydropyridines, roughly paralleled the decreases in the host-cellinfection rates by corresponding dihydropyridines.
Nicardipine and amlodipine were markedly cytotoxic, often
resulting in the detachment of infected HeLa cells fromcoverslips and thus probably yielding apparently decreased
infection rate and protozoan growth. Nifedipine and nisoldipine were also somewhat cytotoxic. Taken together, the１８４

Figure 2. Effect of various calcium antagonists on the rateof Trypanosoma cruzi infection of HeLa cells andon the average number of amastigotes per infected
cell. Inoculation of HeLa cells, infection by T.
cruzi trypomastigotes, and addition of test compounds (10 µM each) were as in Fig. 1. On day 4
after the infection, the rate of HeLa cell infection(A) and the average amastigote number per infected cell (B) were determined as described inMaterials and Methods. Data shown are the means+1 SD of 3 separate determinations.

results indicate that nimodipine is the most potent dihydropyridine against T. cruzi infection and proliferation in HeLa
cells in vitro, with the lowest cytotoxicity to the host HeLa
cells under the conditions examined. Verapamil and gallopamil (the diphenylalkylamine class), diltiazem and midazolam (the benzothiazepine class), and allopurinol were lesseffective than nimodipine and benznidazole in decreasing
the infection rate and the amastigote proliferation (Fig. 2).

Figure 3. Microscopic images of HeLa cells infected by
Trypanosoma cruzi and treated with nimodipine,
allopurinol or benznidazole. HeLa cells (5 x 10３/well) were seeded in each well of 24-well plates,
cultured for 2 days, and infected by T. cruzi trypomastigotes (3 x 10６ parasites/well). Immediately
after the infection, ethanol (final concentration of1%) as control (A) or 10 µM each of nimodipine(B), allopurinol (C) or benznidazole (D) was
added to each well, followed by further incubationfor 4 days. The specimens were fixed, stained, andphotographed as described in Materials and Methods. Bar: 20 µm.

Benznidazole also seemed to be one of the strongest
inhibitors on the average amastigote number per infected
cell (Fig. 2B). Figure 3 shows the typical microscopic images of HeLa cells infected by T. cruzi and treated with ni-

１８５

modipine, allopurinol or benznidazole. In nimodipine- andbenznidazole-treated cultures, few T. cruzi amastigotes
were recognized, while allopurinol appeared to cause asomewhat reduced amastigote number, when compared tothe control culture. The microscopic images of nimodipineand allopurinol-treated HeLa cells resembled those of thecontrol cells, but surprisingly, benznidazole-treated HeLa
cells often showed enlarged nuclei and cytoplasm (Fig. 3D)
and also shrinking, probably necrotic, figures (data notshown). We measured the individual areas of 700 randomly
chosen nimodipine- and 700 benznidazole-treated HeLa
cells and those of 770 normal control HeLa cells, using theImage-Pro Plus software (Media Cybernetics) (data notshown). A statistical analysis revealed that the χ squarevalue for nimodipine versus control was 51.9 (P<0.005)
while that for benznidazole versus control was 1617.9 (P<0.005), a significant difference indicating that benznidazole
yielded a much stronger cytotoxicity to HeLa cells than nimodipine.

Figure 4. Effect of different mammalian cell lines as in vitro
hosts on the rate of Trypanosoma cruzi infection.
HeLa cells (open bar), human fibrosarcoma HT
1080 cells (dotted bar), and mouse fibroblast
Swiss 3T3 cells (closed bar) (5 x 10３/well) were
inoculated in each well of 24-well plates and incubated for 2 days. Infection of these cells by T.
cruzi (3 x 10６ trypomastigotes/well), addition of
calcium antagonists (10 µM each), and determination of the rate of host cell infection were as in Fig.
1. Data shown are the means±1 SD of 3 separate
determinations.

Effect of different mammalian cell lines, used as in vitro
hosts, on the rate of Trypanosoma cruzi infection and on the
average number of amastigotes per infected cell
To determine whether or not other mammalian cells
could serve as hosts in our in vitro infection and drugscreening system, the infection rates of HeLa, HT 1080, andSwiss 3T3 cells were compared on day 4 after the T. cruzi
infection and addition of various calcium antagonists (Fig.
4). Swiss 3T3 cells demonstrated generally high infection
rates, i.e. 24.1, 24.1, 20.8, 20.7, and11.4%, with the addition of nifedipine, verapamil, diltiazem, allopurinol, andbenznidazole, respectively, as compared to the control(28.4%). Nimodipine had the lowest infection rate of 3.3%.
HT 1080 cells seemed to resemble HeLa cells in that benznidazole and nimodipine brought about the largest reduction in the rates of T. cruzi infection of these cell lines.
Effect of varying concentrations of various Ca２＋ antagonists on the rate of Trypanosoma cruzi infection of mammalian cells and on the growth of host cells
Effects of varying concentrations (0.1-100 µM) of
Ca２＋ antagonists on the rates of HeLa cell infection were
examined and IC５０ values (the concentrations of compounds
that elicited a 50% reduction in the infection rate) were calculated (Table 1). The values for nicardipine, nimodipine,
amlodipine, verapamil, and benznidazole ranged from 1.3
to 2.6 µM, while the values for nifedipine, diltiazem, andallopurinol were much higher. Nicardipine, amlodipine, andverapamil were again cytotoxic to HeLa cells, causing theirdetachment from the coverslips. We examined the direct effects of varying concentrations of calcium antagonists on
non-infected, normal HeLa cells (Table 1). IC５０ values fornifedipine, nicardipine, nimodipine, amlodipine, verapamil,
diltiazem, alloprinol, and benznidazole were 51.7, 10.0,
66.2, 8.8, 22.0, 46.8, approximately 100, and 100 µM, respectively. The relative selective cytotoxicities (the ratios of
the latter IC５０ values divided by the former IC５０ values) werehighest for nimodipine (25.5) and benznidazole (58.8).
When HeLa cells were replaced with Swiss 3T3 cells in ourin vitro infection system, the IC５０ value for nimodipine wasextremely low (8.3 nM), yielding a selective cytotoxicity of
5,750, approximately 40-fold greater that that for benznidazole. This seems to be related to the different origin of thesehost cells, that is, HeLa was established as a cancer cell line,
while Swiss 3T3 originated from normal mouse fibroblasts.
However, further studies are needed before any such conclusion can be reached. The results again indicated that nimodipine is the most potent dihydropyridine against T. cruzi
infection and proliferation in mammalian cells in vitro, withrelatively low cytotoxicity to the host cells.

１
８
６

DISCUSSION
Previous studies by Nunez-Vergara et al. and by
Morris et al. [10,13,14] showed that, in T. cruzi epimastigotes, verapamil (the prototype diphenylalkylamine) inhibited the uptake of Ca２＋ but did not inhibit the protozoan
growth in vitro; nifedipine (the prototype dihydropyridine)and diltiazem (the prototype benzothiazepine) also exerted
no inhibitory effect on the parasite proliferation. In an apparently related finding, verapamil reportedly exerted a cardioprotective effect and ameliorated experimental murine
Chagas’ disease [8,9]. However, further searches for an antiT. cruzi calcium antagonist that brings about protozoan
growth inhibition have not been successful, probably, atleast in part, because of a lack of a suitable screening system.
On the basis of the recent, rapid development of calcium channel blockers in cardiovascular and cerebrovascular disorders [15-20], we attempted to examine the anti-T.
cruzi activities of various calcium antagonists, particularly
the second and third generation dihydropyridines, using an
in vitro infection system of T. cruzi and HeLa cells [4]. To
our knowledge, this is the first report that nimodipine, a second generation dihydropyridine calcium antagonist widelyused for treatment for cerebrovascular disorders, is thestrongest inhibitor against T. cruzi infection and proliferation in mammalian cells in vitro, with relatively low cytotoxicity to the host cells (Figs. 2 and 4; Table 1). Likewise,benznidazole, used in this study as a positive control,
strongly inhibited the parasite infection and growth in HeLa
cells, but, unexpectedly, it caused abnormal enlargement of

nuclei and cytoplasm of the host cells (Fig. 3), a possible indicator of cytotoxicity in an in vitro culture [21] consistent
with the statistically evaluated difference between thenimodipine- and benznidazole-treated-cell areas.
Five dihydropyridines, i.e. nifedipine, nicardipine,
nimodipine, nisoldipine, and nitrendipine, possess a common structural formula (Fig. 5) [19,20]. Interestingly,
highly anti-trypanosomal but cytotoxic nicardipine bears(CH２)２N(CH３)CH２-phenyl group as the R２ group in Fig. 5A,
while nimodipine, the strongest anti-T. cruzi calcium antagonist with the lowest cytotoxicity, has (CH２)２OCH３ at thesame position. It is surprising that these differences might
be behind the great cytotoxicity or almost no cytotoxicity to
the host HeLa cells. The second and third generation calcium antagonists act more slowly than the prototype cal-Table 1. Effect of varying concentrations of calcium antagonists on the rate of Trypanosoma cruzi infection of mammalian cells and on the growth of host cells
Host cells

Compoundadded

IC５０ values（µM)
Rate of infection Growth ofof host cells
host cells

HeLa cells
Nifedipine
Nicardipine
Nimodipine
Amlodipine
Verapamil
Diltiazem
Allopurinol
Benznidazole

22.6±4.4
2.5±0.4
2.6±0.5
1.3±0.5
2.1±0.942.8±25.2
18.2±2.3
1.7±0.451.7±7.7
10.0±0.866.2±13.9
8.8±0.622.0±6.0
46.8±10.2
100＊
100＊

Nimodipine
Benznidazole

0.0083±0.010
1.9±0.2147.7±2.5
296.7±32.1

Swiss 3T3 cells

Values are the means±1SD of 3 separate determinations. ＊Approximate
average values of 3 separate determinations.

Figure 5. Structural formulas of various dihydropyridines. A,
the common structural fomula of dihydropyridines.
Chemical structure of nifedipine, the prototype dihydropyridine, is 1,4-dihydro-2,6-dimethyl-4-(mnitrophenyl)-3,5-pyridinedicarboxylic acid dimethyl ester. B, Structural differences of side
chain groups in dihydropyridines. Note thatnicardipine and nimodipine possess -CH２CH２N(CH３)CHPh (phenyl group) and -CH２CH２OCH３,
respectively, in place of a methyl group of the two
methyl esters of nifedipine. These differences may
have caused a marked cytotoxicity or almost no
toxicity on the host HeLa cells. Amlodipine, athird generation dihydropyridine calcium antagonist, bears distinct side chain groups.

１８７cium channel blockers [15-17, 19,20]. This is probably expressed as slowly acting nimodipine in a time-course experiment (Fig. 1A). It may be worthwhile, therefore, to examine the therapeutic efficacies of the slow acting nimodipine and other dihydropyridines against the chronic
stage of murine model Chagas’ disease.
In this study, we measured the anti-T. cruzi activities
of various calcium channel blockers of dihydropyridine,
diphenylalkylamine, and benzothiazepine classes. The target of these compounds is the L-type calcium channel [15,19, 20, 22]. It was reported, however, that HeLa cells andSwiss 3T3 fibrobrasts appeared to carry no L-type channel[23,24], with no report concerning the L-type channel in
HT 1080 cells. This is consistent with the IC５０ value for nimodipine, which is as high as 2 µM, in the inhibition of thehost-cell-infection rate (Table 1), a value that may not be
low enough to claim the presence of a high affinity L-typechannel [15,19,20]. Whether other types of calcium channels and/or calcium binding proteins are the possible targetsof the calcium antagonists, especially nimodipine, used in
the present study is an important topic for future research.
Another important question is whether the key target of nimodipine exists in the mammalian host cells or in the T.
cruzi trypomastigotes. Studies are underway using the parasites pre-incubated with nimodipine.

ACKNOWLEDGMENTS
We thank M. Hashimoto for critical discussion during the course of this study. TA is supported in part by theJapan-US Medical Cooperative Science Program on Parasitic Diseases.

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Tropical Medicine and Health Vol. 32 No. 2, 2004, pp. 189-197
Copyright! 2004 by The Japanese Society of Tropical Medicine

１
８
９

A LIST OF AND KEYS TO BLACK FLIES(DIPTERA: SIMULIIDAE) IN THAILAND
HIROYUKI TAKAOKA１ and WEJ CHOOCHOTE２
Accepted 13, May, 2004

Abstract: Forty-five known species of Simulium Latreille s. l. in Thailand are listed, and keys to subgenera andspecies within each subgenus are provided for adults, pupae and mature larvae.
Key words: Simulium, black fly, Thailand, key, identification

Takaoka and Suzuki [1] provided the first keys to identify all the 19 species of Simulium Latreille s. l. so far recorded from Thailand. During the last two decades, thenumber of species newly described or recorded from thiscountry has increased dramatically to 45 [2]-[9]. New keys
to identify all the known species are essential for further
taxonomic and ecological studies on Simuliidae in Thailand.
We present a list of the species of Simulium s. l. andkeys to subgenera and species for adult females, males, pupae and mature larvae. The definitions of the subgenera andspecies-groups refer to those of Takaoka [10], and terms ofmorphological features used in the keys follow Takaoka[10].

LIST OF THE SPECIES OF SIMULIIDAE IN THAILAND
Genus Simulium Latreille s. l.
Subgenus Daviesellum Takaoka and Adler
１）courtneyi Takaoka and Adler, 1997
２）pahangense Takaoka and Davies, 1995
Subgenus Gomphostilbia Enderlein(A) batoense species-group３）angulistylum Takaoka and Davies, 1995４）decuplum Takaoka and Davies, 1995
５）dentistylum Takaoka and Davies, 1995
６）gombakense Takaoka and Davies, 1995
７）parahiyangum Takaoka and Sigit, 1992
８）siamense Takaoka and Suzuki, 1984(B) ceylonicum species-group９）asakoae Takaoka and Davies, 1995
１０）inthanonense Takaoka and Suzuki, 1984１１）sheilae Takaoka and Davies, 1995
(C) varicorne species-group１２）burtoni Takaoka and Davies, 1995
１３）chumpornense Takaoka and Kuvangkadilok, 2000
Subgenus Montisimulium Rubtsov
１４）sp. G
Subgenus Nevermannia Enderlein(A) feuerborni species-group１５）feuerborni Edwards, 1934(B) ruficorne species-group１６）aureohirtum Brunetti, 1911(C) vernum species-group１７）caudisclerum Takaoka and Davies, 1995
Subgenus Simulium Latreille s. str.
(A) griseifrons species-group１８）choochotei Takaoka, 2002
１９）digrammicum Edwards, 1928２０）grossifilum Takaoka and Davies, 1995
２１）maenoi Takaoka and Choochote, 2002
２２）nigrogilvum Summers, 1911２３）rudnicki Takaoka and Davies, 1995
２４）suchariti Takaoka and Choochote, 2004２５）yongi Takaoka and Davies, 1997
(B) malyschevi species-group２６）siripoomense Takaoka and Saito, 1996
(C) multistriatum species-group２７）chainarongi Kuvangkadilok and Takaoka, 1999２８）chaliowae Takaoka and Boonkemtong, 1999
２９）fenestratum Edwards, 1934３０）malayense Takaoka and Davies, 1995
３１）triglobus Takaoka and Kuvangkadilok, 1999(D) nobile species-group３２）nobile De Meijere, 1907
３３）nodosum Puri, 1933

１．Department of Infectious Disease Control, Faculty of Medicine, Oita University, Hasama, Oita, 879-5593, Japan
２．Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand

１９０(E) striatum species-group３４）chiangmaiense Takaoka and Suzuki, 1984
３５）nakhonense Takaoka and Suzuki, 1984
３６）quinquestriatum (Shiraki, 1935)
３７）thailandicum Takaoka and Suzuki, 1984(F) tuberosum species-group３８）brevipar Takaoka and Davies, 1995
３９）rufibasis Brunetti, 1911
４０）setsukoae Takaoka and Choochote, 2004
４１）tani Takaoka and Davies, 1995
４２）weji Takaoka, 2001(G) variegatum species-group４３）barnesi Takaoka and Suzuki, 1984４４）chamlongi Takaoka and Suzuki, 1984
(H) Simulium s. str. unplaced to group４５）baimaii Kuvangkadilok and Takaoka, 1999

the female leg coloration, there is no morophological difference in the female, male and pupal stages between S.
(S.) sp. E and S. (S.) rufibasis.
＊５．Simulium baimaii, left unassigned to any subgenus by
Takaoka and Kuvangkadilok [4], is treated under the subgenus Simulium s. str. for convenience’ sake.

KEYS TO THE SUBGENERA
OF SIMULIUM S. L. IN THAILAND
ADULT FEMALES＊
１．Katepisternum haired
Gomphostilbia
Katepisternum bare2
２．Claw with a large basal tooth
Nevermannia
Claw simple or with a small subbasal tooth
3
３．Paraproct with a cluster of dark spines
Daviesellum
Paraproct without any dark spine
Simulium s. str.
(*The female of Montisimulium is not included becausethat of S. (M.) sp. G is unknown)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!

!!!!!!!!

Notes:＊

１．Simulium (Montisimulium) sp. G is known only fromlarval specimens collected at Ang Ka, Doi Inthanon National Park [11].
＊２．Simulium (Gomphostilbia) burtoni is newly recorded
based on three adult females collected on a human attractant at Tambol Ban Laung, Doi Inthanon National Park,in January and February 2004, by W. Choochote, and afemale specimen emerged from the pupa collected atHauy Mor, Chiang Mai Province, in June 2001, by W.
Choochote and H. Takaoka. Identification of S. burtoni istentative because adult female specimens of S. burtoni
collected from northern Thailand seem to differ from theoriginal description [12] in that they have a shiny fifth
tergite and dark subbasal spot on the hind tibiae. However, our reexamination of the type female specimen
shows that the fifth tergite of S. burtoni is shiny (it waswrongly noted to be dull in the original description). It isalso shown that there appears to be no dark subbasal spot
on the hind tibiae of the type specimen, as described in
the original description. However, it is difficult to conclude that its hind tibiae lack the dark subbasal spot since
the type specimen was dried and pinned soon after it had
emerged from the pupa, and then preserved in 70% ethanol. It is possible that the dark subbasal spot was as yet
undeveloped in the freshly emerged adult or that it faded
in alcohol. Additional adult specimens of S. burtoni fromthe type locality of Malaysia are needed to solve thisproblem.
＊
３．Simulium (Simulium) sp. D, reported from six females
collected while biting on human attractant in Doi Inthanon National Park by Takaoka and Suzuki [1], was described as a new species, S. (S.) setsukoae, by Takaoka
and Choochote [9].
＊４．Simulium (Simulium) sp. E, which shows a much paler
coloration of the female legs than S. (S.) rufibasis [1], is
tentatively included in S.(S.) rufibasis, since apart from!!!!!!!!!!!

ADULT MALES＊
１．Katepisternum haired
Gomphostilbia
Katepisternum bare2
２．Coxite longer than style
Nevermannia
Coxite shorter than style3
３．Coxite much longer than wide
Daviesellum
Coxite as long as, or slightly shorter than, wide
Simulium s. str.
(*The male of Montisimulium is not included because thatof S. (M.) sp. G is unknown)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

PUPAE＊
１．Grapnel-like hooklets present on the last abdominal
segment
Gomphostilbia
Grapnel-like hooklets absent on the last abdominal
segment2
２．Cocoon with an anterodorsal projection
Nevermannia
Cocoon without any anterodorsal projection
3
３．Dorsal surface of abdominal segment 2 with stout
hooks similar in size to those on abdominal segments
3 and 4
Daviesellum
Dorsal surface of abdominal segment 2 with spines (inplace of such distinct hooks) much smaller thanhooks on abdominal segments 3 and 4
Simulium s. str.
(*The pupa of Montisimulium is not included because thatof S. (M.) sp. G is unknown)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

１
９
１

MATURE LARVAE
１．Hypostomium very wide, with 13 apical teeth
Daviesellum
Hypostomium of moderate width, with 9 apical teeth
2２．Last abdominal segment lacks ventral papillae or withsmall ones
Simulium s. str.
Last abdominal segment with large ventral papillae 3
３．Postgenal cleft vestigeal
Montisimulium
Postgenal cleft distinctly formed
4
４．Lateral margin of hypostomium serrated
Nevermannia
Lateral margin of hypostomium smooth
Gomphostilbia!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!

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dark
dentistylum
Mid and hind femora alomst dark except base pale 4
４．Hind tibia mostly dark
siamense
Hind tibia whitish yellow or dark yellow on basal 2/5
or more5５．Hind tibia with a dark subbasal spot
6
Hind tibia without such a dark subbasal spot
8
６．Sensory vesicle of medium size, 0.3 times as long as
3rd maxillary palpal segment
angulistylum
Sensory vesicle enlarged, 0.5 or 0.6 times as long as
3rd maxillary palpal segment
7
７．Arms of genital fork with a short projection directed
anteriorly
decuplum
Arms of genital fork without such a projection
parahiyangum
８．Hind tibia whitish yellow on basal 2/3; sensory vesicleof moderate size, 0.3 times as long as 3rd maxillarypalpal segment
asakoae
Hind tibia whitish yellow on basal 2/5 or 1/2; sensory
vesicle enlarged, 0.57 or 0.68 times as long as 3rd
maxillary palpal segment
9９．Frons-head ratio 1.0 : 4.8: sensory vesicle enlarged,
0.57 times as long as 3rd maxillary palpal segment
inthanonense
Frons-head ratio 1.0 : 5.7; sensory vesicle enlarged,
0.68 times as long as 3rd maxillary palpal segment
sheilae(*The female of S. gombakense, which is unknown, is notincluded)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

KEYS TO THE SPECIESOF THE SUBGENUS DAVIESELLUMADULT FEMALES
１．Genital fork with a distinct projection directed anteriorly
courtneyi
Genital fork without such a projection
pahangense!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ADULT MALES
１．Ventral plate much longer than wide when viewed ventrally
courtneyi
Ventral plate much shorter than wide when viewed
ventrally
pahangense!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

PUPAE
１．Frons densely covered with tubercles
courtneyi
Frons mostly bare (though narrow portion near the
lower margin tuberculate)pahangense!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ADULT MALES
１．Antenna composed of 10 segments
2
Antenna composed of 11 segments
3２．Ventral plate produced ventrally
burtoni
Ventral plate nearly flatchumpornense
３．Hind basitarsus enlarged
4
Hind basitarsus slender, much thinner than hind tibia
6
４．Eye with 16 horizontal rows of large facets
inthanonense
Eye with 13 horizontal rows of large facets
5
５．Hind tibia mostly medium brown to brownish blackwith basal 1/3 or a little less somewhat pale sheilae
Hind tibia whitish on a little less than basal 1/2 andbrownish black on the rest
asakoae
６．Mid and hind femora yellow except apical cap dark
dentistylum
Mid and hind femora almost dark except base pale 7
７．Hind tibia almost dark except base pale
8
Hind tibia whitish on basal 1/2 or more
10
８．Abdominal segments 2, 5, 6 and 7 each with a dorso!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!

MATURE LARVAE
１．Postgenal cleft long, but its apex not reaching the posterior margin of hypostomium
courtneyi
Postgenal cleft long, its apex reaching the posterior
margin of hypostomium
pahangense!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!

KEYS TO THE SPECIESOF THE SUBGENUS GOMPHOSTILBIA!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

＊ADULT FEMALES
１．Antenna composed of 10 segments
2
Antenna composed of 11 segments
3
２．Tergite 5 shiny
burtoni
Tergite 5 not shiny
chumpornense
３．Mid and hind femora almost yellow except apical cap!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!

１
９２

lateral pair of shiny whitish-pruinose patches
siamense
Abdominal segments 2, 6 and 7 each with a dorsolateral pair of shiny whitish-pruinose patches
9９．Upper eye with 12 or 13 vertical columns and 15 horizontal rows of large facets
decuplum
Upper eye with 17 vertical columns and 15 horizontal
rows of large facets
parahiyangum
１
０．Hind tibia whitish on basal 2/3, with a dark subbasal
spot
angulistylum
Hind tibia whitish yellow on basal 1/2, without such adark subbasal spot
gombakense!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

medium-long stalk9
９．Cocoon with a distinct anterodorsal projection
inthanonense
Cocoon with an anterodorsal bulge
10
１０．Terminal hooks weakly undulate on outer marginsheilaeTerminal hooks weakly serrate on outer margin
asakoae!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

MATURE LARVAE
１．Thoracic segment 3 and abdominal segments 1―5 eachwith 1 or 2 pairs of dorsal and/or dorsolateral protuberances
2
Thoracic segment 3 and abdominal segments 1―5 without any dorsal or dorsolateral protuberance
3
２．Postgenal cleft very long, its apex reaching the posterior margin of hypostomium; thorax and abdomen
densely covered with dark spines of various sizes
parahiyangum
Postgenal cleft long, but its apex not reaching the posterior margin of hypostomium; thorax and abdomen
sparsely or moderately covered with minute setae
chumpornense
３．Postgenal cleft very long, its apex nearly or completely
reaching the posterior margin of hypostomium
4
Postgenal cleft otherwise
5
４．Abdomen markedly constricted between segments 4
and 5
dentistylum
Abdomen not constricted between segments 4 and 5
sheilae
５．Postgenal cleft short, much shorter than postgenal
bridgeinthanonense
Postgenal cleft longer than postgenal bridge
6
６．Abdomen almost bare except the last segment; pharate
pupal gill of inflated structure
gombakense
Abdomen moderately or densely covered with simple
or branched dark spinous setae or spinules dorsally7
on segments 5―8; pharate pupal gill filamentous
７．Abdomen moderately covered with simple minute dark
asakoaesetae dorsally on segments 5―8
Abdomen moderately or densely covered with brancheddark spinous setae or spinules dorsally on segments
8
5―8
８．Thoracic cuticle moderately covered with minute dark
spinules with 7―11 branches dorsally; pharate pupal
gill with 10 filaments
decuplum
Thoracic cuticle almost bare dorsally; pharate pupal
gill with 8 filaments
9９．Minute dark spinous setae on abdominal segments 5―8
somewhat flat and stout basally, with short branches
apically
siamense!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

PUPAE
１．Gill of much inflated structure with 2 triplet groups offinger-like projections and 8 slender filaments
gombakense
Gill with 8 or 10 filaments
2
２．Gill with 10 filaments
decuplum
Gill with 8 filaments
3
３．Gill filaments all shorter than pupal body (shorter than
1.6 mm), short-stalked
4Gill filaments subequal to, or longer than, pupal body(longer than 1.9 mm), moderately-stalked
7
４．Antennal sheath smooth5
Antennal sheath with tubercles
6
５．Gill filaments arranged in 2 groups, i.e.1dorsal (4 individual and 2 paired filaments) and 1ventral (2 paired
filaments)
chumpornense
Gill filaments arranged in 3 groups (3+3+2 filamentsfrom dorsal to ventral)angulistylum
６．Antennal sheath with marked ridges each corresponding to flagellar segments 1―9, each ridge covered
with several tubercles; gill filaments arranged in 3
groups (3+3+2 filaments from dorsal to ventral)parahiyangum
Antennal sheath with less marked ridges corresponding to flagellar segments 1―9, each ridge covered
with a few tubercles; gill filaments arranged in 4
groups (2+1+3+2 filaments from dorsal to ventral)
dentistylum
７．Dorsal and middle triplet groups and ventral pair grouparising basally at the same level
siamense
Dorsal and middle triplet groups sharing a short stalk,which arises, with a stalk of ventral pair group, fromshort common basal stalk8
８．Dorsal and middle triplet groups consisting of 1 individual filament and 2 paired filaments with a very
long stalkburtoniDorsal and middle triplet groups consisting of 1 individual filament and 2 paired filaments with a short or!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!

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!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!

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１
９３

Minute dark spinous setae on abdominal segments 5―8
slender and hair-like basally, with long branches 10
１０．Minute dark spinous setae on abdominal segments 5―8
burtoniwith 0―5 branches
Minute dark spinous setae on abdominal segments 5―8
angulistylum
with 5―12 (mostly 8―10) branches!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

composed of 1 well-developed and 1 small teeth andwith supernumerary serrations
caudisclerum
Abdomen without any accessory sclerite; mandibular
serrations composed of 2 well-developed teeth andwithout supernumerary serrations
aureohirtum!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!

!!!!!!!!!!!

KEYS TO THE SPECIESOF THE SUBGENUS SIMULIUM S. STR.

KEYS TO THE SPECIESOF THE SUBGENUS NEVERMANNIA
ADULT FEMALES
１．Antenna yellow with at least 1st flagellar segment
darkened; hind tibia yellow on basal 1/2, dark on apical 1/2, and with subbasal dark ringaureohirtum
Antenna almost all darkened or mostly so except a few
basal segments pale; hind tibia nearly all brown
2
２．Scutum reddish brown in ground color, with 3 dark
longitudinal vittae
feuerborni
Scutum brownish black in ground color, without any
longitudinal vitta
caudisclerum!!!!!!!!!!

!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ADULT MALES
１．Antenna yellow or yellowish brown with 1st flagellar
segment darkened; hind basitarsus slender, parallelsided, much narrower than hind tibia
aureohirtum
Antenna almost all darkened; hind basitarsus inflated,
its greatest width nearly as wide as that of hind tibia
2
２．Scutum whitish pruinose with 3 dark longitudinal
vittae at certain angle of light; paramere with 3 or 4
parameral hooks
feuerborni
Scutum whitish pruinose without any longitudinal
vitta; paramere with a single parameral hookcaudisclerum!!!!!!!!

!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

PUPAE
１．Gill with 4 filaments
caudisclerum
Gill with 6 filaments2
２．All filaments extending forwards close together, and 2
ventral filaments with rather long stalkfeuerborni
All filaments diverging widely from the base, and 2
ventral paired filaments with short stalk aureohirtum!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!

!!!!

ADULT FEMALES＊
１．Claw with a small subbasal tooth
2
Claw without any tooth6
２．Basal section of radial vein fully haired; fore basitarsus
with thick dorsal hair crest
nigrogilvum
Basal section of radial vein bare; fore basitarsus withmoderate dorsal hair crest
3
３．Mid and hind femora mostly yellowish
chamlongi
Mid and hind femora mostly brownish
4
４．Scutum densely covered with yellow hairsbarnesi
Scutum moderately covered with brassy hairs
5
５．Antenna brownish black with scape, pedicel and baseof 1st flagellar segment yellow; abdominal segment 7
with branched hairs medially on ventral surface
siripoomense
Antenna yellow or tawny with 2 apical segments
blackish; abdominal segment 7 with simple hairs on
ventral surface
nobile６．Scutum with distinct longitudinal vittae
7
Scutum without any vitta
17
７．Fore tibia medium to dark brown, without white area
on outer surface; hind tibia dark brown to brownish
black with base yellow; inner margin of ovipositor
valve with ventrally produced round flap
chiangmaiense, nakhonense and quinquestriatum
Fore tibia with white shiny area on outer surface; hindtibia whitish or yellowish on basal 2/3 or more anddark brown to brownish black on the rest; inner margin of ovipositor valve without such a flap
8８．Basal section of radial vein fully haired
9
Basal section of radial vein bare
11
９．Hind basitarsus whitish on basal 3/5 and dark brownon the rest; ovipositor valve rounded, covered withshort setae, and with elongate internal projection
grossifilum
Hind basitarsus whitish on basal 1/2 and dark brownon the rest; ovipositor valve triangular, covered withlong stout hairs, and without such an internal projection
10
１０．Cibarium with a round short medial projection alongposterior margin
choochotei!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!

!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!

MATURE LARVAE
１．Abdomen with distinct reddish-brown markings dorsally
feuerborni
Abdomen without any distinct colored marking dorsally2
２．Abdomen with accessory sclerite ventrolaterally oneach side of the last segment; mandibular serrations!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

１
９
４

Cibarium with a narrow long medial projection alongposterior margin
digrammicum
１１．Mid tibia white on basal 2/3 or 3/4 and dark brown orbrownish black on the rest; cibarium with a tuberculate medial projection
12
Mid tibia white on basal 4/5 or 5/6 and light to darkbrown on the rest; cibarium with a smooth medial
projection
13
１２．Cibarium with tubercles near the base of medial projection
suchariti
Cibarium bare near the base of medial projection
maenoi１３．All femora almost yellow; three spermathecae present
triglobus
At least mid and hind femora mostly dark; one spermatheca present
14
１４．Hind basitarsus whitish yellow on a little more thanbasal 1/2 and dark brown on the rest
fenestratum
Hind basitarsus whitish yellow on basal 3/5 and darkbrown on the rest15
１５．Sternite 8 with 10―16 long hairs on each sidemalayense
16
Sternite 8 with 23―34 long hairs on each side
１６．Mid femur blackish brown with basal 1/5 or 1/4 yellow
chaliowae
Mid femur almost entirely dark brownchainarongi
１７．Mid tarsal segments 2 and 3 entirely yellow nodosum
Mid tarsal segments 2 and 3 light brown to brownish
black
18
１８．Mid femur entirely yellow
rudnickiMid femur almost dark brown
19
１９．Abdominal segment 7 with a pair of clustered hairs
ventrally
20
Abdominal segment 7 without such a pair of clusteredhairs ventrally
22
２０．A pair of clustered hairs on abdominal segment 7 short,
subequal in length to those on the surrounding area
setsukoae
A pair of clustered hairs on abdominal segment 7
much longer than those on the surrounding area 21
２１．Mid tibia almost light brown with base somewhat yellow
weji
Mid tibia white on basal 1/2 or more and medium
brown on the rest
rufibasis
２２．Hind basitarsus white on a little more than basal 1/2
and brownish black on the rest; scutum covered withyellowish hairs as well as dark ones
yongi
Hind basitarsus white on basal 3/5 or more andbrownish black on the rest; scutum covered with darkbrown hairs only
23
２３．Sensory vesicle enlarged, 0.7 times as long as the 3rd!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!!

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!!!!!!!!!!!!!!!!!

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!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!

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!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

maxillary palpal segment
tani
Sensory vesicle medium-sized, 0.3 times as long as the
3rd maxillary palpal segment
brevipar(*The females of S. baimaii and S. thailandicum, which areunknown, are not included)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!

ADULT MALES＊
１．Basal portion of radial vein fully haired
2
Basal portion of radial vein bare4
２．Abdomen with a pair of shiny whitish-grey pruinose
spots dorsally or dorsolaterally on segments 2, 5, 6
and 7; width of style nearly the same from base toapical tip when viewed ventrolaterally
choochotei
Abdomen with a pair of shiny white pruinose spots
dorsally or dorsolaterally on segments 2, 6 and 7;
width of style becoming much narrower apically3
３．Fore basitarsus with thick dorsal hair crest; hind basitarsus nearly parallel-sided; ventral plate nearly quadrate, parallel-sided when viewed ventrally
nigrogilvum
Fore basitarsus with moderate dorsal hair crest; hindbasitarsus spindle-shaped; ventral plate gradually narrowed posteriorly when viewed ventrally
digrammicum
４．Scutum broadly silvery pruinose with transverse,
inverted-V-shaped, black band
5
Scutum otherwise
6
５．Ventral plate with a narrow body parallel-sided whenviewed ventrally
nobileVentral plate with a wide body broadened mediallywhen viewed ventrally
nodosum
６．Mid femur and tibia almost yellow
rudnickiMid femur and tibia otherwise
7
７．Mid tibia mostly dark (including posterior surface) 8
Mid tibia whitish or yellowish (at least on posterior
surface) on basal 1/2 or more and dark brown on therest
16
８．Fore tibia medium brown, with white shiny area onouter surface
9
Fore tibia medium to dark brown, without white area
on outer surface
15
９．Hind basitarsus white or whitish yellow on basal 1/2 orless and dark brown to brownish black on the rest 10
Hind basitarsus white or whitish yellow on more thanbasal 1/2 and light to dark brown on the rest13
１０．Hind basitarsus somewhat enlarged, about 5.0 times aslong as wide and much narrower than hind tibia
chamlongi
Hind basitarsus much enlarged, 3.2―3.5 times as longas wide, and subequal to, or a little wider than, thegreatest width of hind tibia
11!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!

!!!!!!!

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!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

１
９
５

１１．Upper eye with 20 vertical columns of large facets
setsukoae
Upper eye with 15―17 vertical columns of large facets
12
１２．Hind basitarsus whitish yellow on basal 1/3 andbrownish black on the rest
rufibasis
Hind basitarsus whitish yellow on basal 1/2 or a little
less and brownish black on the rest
tani
１３．Hind basitarsus, narrow (similar to that of female),parallel-sided, white with apical 1/6 light brownsiripoomense
Hind basitarsus enlarged, wedge-shaped, whitish yellow on basal 3/5 or a little less and dark brown on therest
14
１４．Abdominal segments 2, 5, 6 and 7 each with a pair ofsilvery iridescent spots dorsolaterally
weji
Abdominal segments 2, 6 and 7 each with a pair of silvery iridescent spots dorsolaterally
brevipar１５．Hind basitarsus whitish yellow on basal 1/2 or a little
more or less and brownish black on the rest
quinquestriatum
Hind basitarsus whitish yellow on basal 3/5 andbrownish black on apical 2/5
chiangmaiense, nakhonense and thailandicum１
６．Hind basitarsus whitish on basal 1/2 or a little less andbrownish black on the rest; body of ventral plate
wider than long
17
Hind basitarsus entirely light to dark brown, or so withbasal 2/5 whitish yellow or dark yellow; body of ventral plate longer than wide
18
１
７．Body of ventral plate about 1.8 times as wide as long,and much shorter than arms
yongi
Body of ventral plate about 2.3 times as wide as long,and much longer than arms
grossifilum
１８．Hind basitarsus entirely light to dark brown
19
Hind basitarsus brownish black with basal 2/5 whitish
yellow or dark yellow
20
１９．Ventral plate subquadrate when viewed ventrally, andwith distinct teeth on its posterior surface chaliowae
Ventral plate gradually narrowed posteriorly whenviewed ventrally, and without any tooth on its posterior surface
maenoi２０．Upper eye with 20 vertical columns and 20 horizontal
rows of large facets
chainarongi
Upper eye with 15―17 vertical columns and 16 or 17
horizontal rows of large facets
21
２１．Upper eye with 15 vertical columns and 16 horizontal
rows of large facets; ventral plate with 2 vertical rowsof teeth nearly parallel-sided on its posterior surface
malayense
Upper eye with 17 vertical columns and 17 horizontal!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

rows of large facets; ventral plate with teeth irregularly situated on its posterior surface
fenestratum(*The males of S. baimaii, S. barnesi and S. suchariti,
which are unknown, are not included)!!!!!!!!!!

PUPAE
１．Gill of inflated form
2
Gill filamentous
4２．Gill with 2 filaments arising from long inflated trunkbaimaii
Gill with 3 or 6 inflated tubes with rounded apex
3
３．Gill with 3 inflated tubes
nodosum
Gill with 6 inflated tubes with minute spines
grossifilum
４．Gill with 6 filaments
5Gill with 8 or 10 filaments
19
５．Cocoon simple wall-pocket-shaped
6
Cocoon shoe-shaped or boot-shaped
16
６．Cocoon with an anterolateral window on each side 7
Cocoon without lateral window
10
７．Gill filaments subequal in length and thickness to one
another
8Gill filaments decreased in thickness from dorsal toventral
9８．Gill filaments short-stalked; dorsal spine-combs presiripoomense
sent on abdominal segments 7―9
Gill filaments almost sessile; dorsal spine-combs present only on abdominal segment 8
rudnicki
９．Cocoon with a small anterolateral window on eachside; frons moderately covered with very large tubercles; terminal hooks present
maenoi
Cocoon with a moderate anterolateral window on eachside; frons densely covered with small and mediumsized tubercles; terminal hooks absent
suchariti
１０．Integuments of head and thorax bare (except posterior
1/2 of thorax with minute tubercles)
11
Integuments of head and thorax moderately or densely
covered with tubercles
12１
１．Cocoon very thin, transparent, and its anterior margin
often not well defined; inner filament of the ventralmost pair narrowed basally; dorsal spine-combs present on abdominal segment 8; terminal hooks absent
yongi
Cocoon thickly woven, not transparent, and its anterior
margin well defined; inner filament of the ventralmost pair not narrowed basally; dorsal spine-combs
present on abdominal segments 7―9; terminal hooks
present
chamlongi
１２．Terminal hooks present
tani
Terminal hooks absent
13
１３．Gill filaments with short-stalked; dorsalmost filament!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!

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１
９
６

basally directed upward or forward, then curved forward or downward; abdominal segment 7 with spinecombs dorsally
14
Gill filaments almost sessile; dorsalmost filament basally directed forward or downward; abdominal segment 7 without spine-combs dorsally
15
１
４．Two filaments of the dorsal pair subequal in thickness
to each otherrufibasis
Dorsalmost filament of the dorsal pair much thicker
than the counter filament
setsukoae
１
５．Thoracic integument with pit-like organ at base of gill
breviparThoracic integument without such organ at base of gillweji
１
６．Cocoon loosely woven, with many small open spaces
in webschoochotei
Cocoon tightly woven
17
１
７．Cocoon with an anterolateral flap and a small anterolateral window on each side; terminal hooks present
digrammicum
Cocoon without such flap and window; terminal hooks
absent18１
８．Abdominal segment 8 with spine-combs dorsally
nobileAbdominal segment 8 without any spine-comb dorsallynigrogilvum
１９．Gill with 8 filaments
20
Gill with 10 filaments
25
２０．Cocoon wall-pocket-shaped
21
Cocoon shoe-shaped
22
２１．Cocoon with an anterolateral window on each side
fenestratum
Cocoon without any windowmalayense
２２．Cocoon roughly woven anteriorly, leaving some large
open spaces in webs of the anterior collar and manysmall open spaces near anterior margin
23
Cocoon without open spaces in the webs
24
２３．Gill filaments subequal in thickness to one anothertriglobus
Two ventralmost paired filaments much thinner thanthe others
chiangmaiense２
４．Basal portion of the dorsalmost filament about 1.4
times as thick as the ventralmost one
chaliowae
Basal portion of the dorsalmost filament about twice as
thick as the ventralmost one
chainarongi
２
５．Gill filaments arranged in 2+3+3+2 filaments fromdorsal to ventral; all filaments subequal in thickness
to one anotherquinquestriatum
Gill filaments arranged in 2+2+2+2+2 filaments; 4 or 5
dorsal filaments slightly to markedly thicker than theothers26

２６．Head integument with round tubercles
nakhonense
Head integument with angular tubercles thailandicum!!!!!!!!!

!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!

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MATURE LARVAE＊
１．Last abdominal segment with a distinct accessarysclerite ventrally
nigrogilvum
Last abdominal segment without any accessary sclerite2
２．Abdominal segments 1―5 (or up to 8) each with 1 ormore pairs of protuberances dorsally or dorsolateraly
3
Abdominal segments lacking protuberances9
３．Abdominal segments 1―8 each with 1―6 pairs of protuberances dorsally and dorsolatelly
siripoomense
Abdominal segments 1―5 (or up to 8) each with a pairof protuberances dorsally or dorsolaterally
4
４．Postgenal cleft very long, its apex reaching the posterior border of hypostomium
5
Postgenal cleft very long, but its apex not reaching theposterior border of hypostomium
6
５．Pharate pupal gill with 6 filaments
nobilePharate pupal gill with 3 filaments
nodosum
６．Pharate pupal gill with 8 filaments
7
Pharate pupal gill with 10 filaments
8
７．Abdominal segments 1―6 each with a pair of protuberances dorsally
chainarongi
Abdominal segments 1―8 each with a pair of protuberances dorsally
chiangmaiense
８．Pharate pupal gill with 10 filaments arranged in 2+3+3+2 filaments
quinquestriatum
Pharate pupal gill with 10 filaments arranged in 2+2+2+2+2 filaments
nakhonense
９．Postgenal cleft moderately widened medially, its greatest width much larger than the width at base10
Postgenal cleft not widened or slightly so medially, its
greatest width subequal to, or slightly larger than, thewidth at base
11
１０．Pharate pupal gill with 6 filaments
chamlongi
Pharate pupal gill with 8 filaments
fensestratum and malayense
１１．Abdomen with its greatest width on segment 8
12
Abdomen with its greatest width on segment 6 or 7
14
１２．Cephalic apotome mostly pale yellow
yongi
Cephalic apotome mostly light to medium brown 13
１３．Posterior circlet with 144―160 rows of hooklets
rudnicki
Posterior circlet with ca. 210 rows of hooklets
choochotei
１４．Body longer than 7.0 mm
suchariti
Body shorter than 7.0 mm
15!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!

!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!

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!!!!!!!!!!!!!!!!!

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!!!!!!!!!!

!!!!!!!

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１
９
７

１５．Postgenal cleft widely rounded apically16
Postgenal cleft nearly pointed apically
19
１６．Pharate pupal gill with 2 filamentsbaimaii
Pharate pupal gill with 6 or 8 filaments
17
１７．Pharate pupal gill with 8 filaments
triglobus
Pharate pupal gill with 6 filaments
18
１８．Body length 5.9―6.4 mm; elongate spot on each side of
postgenal cleft positive; each lobe of rectal organmaenoiwith 8―12 finger-like secondary lobules
Body length 5.0―5.5 mm; elongate spot on each side of
postgenal cleft negative; each lobe of rectal organwith 14―18 finger-like secondary lobules
digrammicum
１９．Postgenal cleft of medium size, nearly as long as wide;
pharate pupal gill with 6 inflated tubular filaments
grossifilum
Postgenal cleft long, much longer than wide; pharate
pupal gill with 6 thread-like filaments
20
２０．Cephalic apotome yellow, with dark area medially justin front of posterior margin
21
Cephalic apotome pale yellow to pale brown, without
dark area medially just in front of posterior margin22
２１．Body color reddish brown; dorsal pair of pharate pupal
gill filaments subequal in thickness to each otherrufibasis
Body color dark grey to greyish black; one of dorsal
pair of pharate pupal gill filaments much thicker thanthe counter filament
setsukoae
２２．Each lobe of rectal organ with 14―16 finger-like secondary lobules; posterior circlet with ca. 86 rows ofhooklets with up to 17 hooklets per row
weji
Each lobe of rectal organ with 7―12 finger-like secondary lobules; posterior circlet with 70―74 rows ofhooklets with up to 12 or 14 hooklets per row
23
２
３．Body color reddish brown
tani
Body color dark grey
brevipar(*The mature larvae of S. barnesi, S. chaliowae and S. thailandicum, which are unknown, are not included)!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!

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!!!!!!!!!

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!!!!!!!!!!

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ACKNOWLEDGEMENT
This work was financially supported by a Grant-in-Aidof Japan US Medical Research Cooperation Program (thefiscal year 2003).

LITERATURE CITED
１）Takaoka H, Suzuki H. The blackflies (Diptera: Simuliidae) from Thailand. Jpn. J. Sanit. Zool. 1984; 35 (1): 745.
２）Takaoka H, Saito K. A new species and new records ofblack flies (Diptera: Simuliidae) from Thailand. Jpn. J.
Trop. Med. Hyg. 1996; 24: 163-9.
３）Takaoka H, Adler PH. A new subgenus, Simulium (Daviesellum), and a new species, S. (D.) courtneyi, (Diptera:
Simuliidae) from Thailand and Peninsular Malaysia. Jpn.
J. Trop. Med. Hyg. 1997; 25 (1): 17-27.
４）Takaoka H, Kuvangkadilok C. Four new species of black
flies (Diptera: Simuliidae) from Thailand. Jpn. J. Trop.
Med. Hyg. 1999; 27 (4): 497-509.
５）Takaoka H, Mulla MS. Taxonomic notes on Simulium
siripoomense from Thailand (Diptera: Simuliidae): Descriptions of female and pupa, and change of its subgeneric status from Byssodon to Simulium s. str. Jpn. J.
Trop. Med. Hyg. 2000; 28 (1): 25-28.
６）Kuvangkadilok C, Takaoka H. Taxonomic notes on Simuliidae (Diptera) from Thailand: Description of a new
species and new distributional records of nine known
species. Jpn. J. Trop. Med. Hyg. 2000; 28 (3): 167-175.
７）Takaoka H. Simulium (Simulium) weji sp. nov. (Diptera:
Simuliidae) from Thailand. Jpn. J. Trop. Med. Hyg.
2001; 29 (4): 349-354.
８）Takaoka H, Choochote W. Taxonomic notes on the griseifrons species-group in Simulium (Simulium) (Diptera:
Simuliidae) from Thailand: Descriptions of two new species and description of the male, pupa and larva of S. (S.)
digrammicum Edwards. Jpn. J. Trop. Med. Hyg. 2002;
30 (2): 115-132.
９）Takaoka H, Choochote W. Two new species of Simulium(Simulium) (Diptera: Simuliidae) from Thailand. Trop.
Med. Hlth. 2004; 32 (1): 31-36.
１０）Takaoka H. The black flies (Diptera: Simuliidae) of Sulawesi, Maluku and Irian Jaya. xxii+581pp., Kyushu University Press; Fukuoka; 2003.
１１）Kuvangkadilok C, Boonkemtong C, Phayuhasena S. Cbanding in polytene chromosomes of six Simulium species (Diptera: Simuliidae) from Doi Inthanon National
Park, northern Thailand. J. Sci. Soc. Thailand. 1998; 24:
215-230.
１２）Takaoka H, Davies DM. The black flies (Diptera: Simuliidae) of West Malaysia. viii+175pp., Kyushu University
Press; Fukuoka; 1995.

Tropical Medicine and Health Vol. 32 No. 2, 2004, pp. 199-202
Copyright! 2004 by The Japanese Society of Tropical Medicine

１
９
９

THE USE OF TRAVEL VACCINES BY JAPANESE EXPATRIATESIN DEVELOPING COUNTRIESATSUO HAMADA, YUKA UJITA, EIICHI OKUZAWA, TOSHIHIRO KOGA, AKIRA UCHIKOSHISHINJI FUKUSHIMA, KIYOMI HONDO, TETSUO NISHIKAWA and NORIHIKO BASUGIAccepted 3, March, 2004

Abstract: From 1998 to 2001, using questionnaires, we surveyed the use of travel vaccines among Japanese expatriates in developing countries. The percentage of those using more than one type of travel vaccine before departure increased significantly (45.6% in 1998 to 53.4% in 2001 (p<0.001)). In regions such as tropical Africa andSouth Asia, vaccination rates were high. But the increase was most noticeable in East Asia, the Middle East, andLatin America. Vaccinations against hepatitis A, hepatitis B, and tetanus were high throughout the developing
countries. Vaccinations against yellow fever and Japanese encephalitis were high in endemic regions. Vaccination
rates were slightly higher for typhoid fever in South Asia and tropical Africa than that in other areas. Vaccination
rates for cholera, however, showed yearly declines. These trends seem to reflect a growing awareness among expatriates of the benefits of travel vaccines. Even so, nearly half of those living the countries have not received sufficient vaccination, indicating a need for further education.

INTRODUCTION
Global business has resulted in an increase in the number of Japanese living abroad long-term. According to statistics from the Ministry of Foreign Affairs, the number ofJapanese expatriates in 2002 was 590,000 people, approximately three times as many as in 1980. Of these, about
200,000 people live in developing countries, and are at riskof various local infectious diseases [1].
In order to lower the risk of infectious diseases overseas, travel vaccine can be administered. However, vaccination rates tend to be low among Japanese expatriates. Ac-

cording to research by Basnyat from 1997 to 1998 in Katmandu, 95% of Japanese travelers were not vaccinatedagainst hepatitis A or typhoid fever [2]. Among nonJapanese people, 90% had been vaccinated against these
diseases. Therefore, we developed a questionnaire-based
investigation to further clarify the situation.

METHODS
Each year, we perform a health consultation service forJapanese expatriates residing in urban areas of developing
countries. The subjects of this survey were Japanese expa-

Table 1. Number of Japanese who responded to the questionnaire each year
Area
Total

Countries

1998
3061

1999
2895

2000
2982

2001
2755

East Asia

China

591

490

466

382

South East Asia

Indonesia, Malaysia, Myanmar
Philippines, Thailand, Vietnam

917

823

958

878

South Asia

Bangladesh, India, Nepal, Pakistan
Sri Lanka

496

513

521

442

The Middle East

Bahrain, Egypt, Iran, Morocco, Oman
Qatar, Saudi Arabia, Turkey, UAE

539

549

530

587

Tropical Africa

Ethiopia, Ghana, Ivory Coast, Kenya
Nigeria, Tanzania

196

170

146

180

Latin America

Colombia, Costa Rica, Ecuador
Guatemala, Mexico. Puerto Rico
Panama, Venezuela

322

350

361

286

Japan Labor Health and Welfare Organization, Japan Overseas Health Administration Center２００

triates who responded to the consultation from 1998 to
2001. The research was limited to those 16 years of age orolder. Many of the subjects were employees sent fromJapanese companies, and their families.
From 1998 to 2001, during the consultation, questionnaires were given to the subjects. On the questionnaire, thetravel vaccines were listed, and the subjects were requested
to note the vaccines they had received before departure. Table 1 shows the number of responses corresponding to theyear they were received.
The list contained the following 10 vaccines: hepatitis
A, hepatitis B, tetanus, rabies, yellow fever, Japanese encephalitis, cholera, typhoid fever, and meningococcal meningitis.
We used the chi-square method to analyze the data.

1998 was only about 30%. The subsequent years showed
dramatic increases, and by 2001 both regions showed rates
higher than 45%. In Latin America, the rate also rose from
44.7% in 1998 to 56.6% by 2001.
(2) Individual vaccines’ vaccination rate
The vaccination rates of individual vaccines excluding
cholera and meningococcal meningitis showed an increase
from 1998 to 2001 (Table 3). In 2001, the rate for hepatitis
A was the highest at 40.3%, hepatitis B and tetanus were in
the 30% range, followed by rabies at 18.2%. The rate forcholera decreased, coming to 2.1% in 2001, and that formeningococcal meningitis did not change during the period.
All regions showed increases in rates for hepatitis A,
hepatitis B, tetanus, and rabies (Table 4). In 2001, the rate
for hepatitis A in tropical Africa was highest at 53.9% andlowest in the Middle East at 30.0%. The rate for hepatitis B
was highest in tropical Africa at 50.6%, lowest in the Middle East at 22.7%. The rate for tetanus was highest in South
Asia at 54.8% and lowest in East Asia at 22.5%. Rabies
was highest in South Asia at 37.3% and lowest in East Asia
at 3.9%.
For yellow fever, vaccination rates in endemic regions
such as tropical Africa and Latin America were high. In
tropical Africa, rates increased only slightly: from 79.1% in1998 to 81.1% in 2001. In Latin America, rates increased
more dramatically: from 15.2% in 1998 to 25.9% in 2001.
Vaccination rates were high for Japanese encephalitis

RESULTS(1) Total vaccination rate
Table 2 shows the percentage of respondents who received one or more types of travel vaccine before departure.
The vaccination rate elevated from 45.6% in 1998 to 53.4%
by 2001. The value in 2001 is significantly higher than thatin 1998 (p<0.001).
On a regional basis, in 1998, the vaccination rates intropical Africa and South Asia were high and did not varymuch during the period of this survey. On the other hand,in East Asia and the Middle East, the vaccination rate inTable 2. Japanese who received one or more types of travel vaccine (1998 to 2001)
Total
By area
East Asia
South East Asia
South Asia
The Middle East
Tropical Africa
Latin America

1998 (%)
45.6

1999 (%)
48.3

2000 (%)
49.2

2001 (%)
53.4

P value (1998 vs 2001)<0.001

31.6
45.6
64.9
28.9
86.7
44.7

34.5
43.6
67.1
37.0
90.0
48.6

35.2
43.2
66.0
40.8
91.8
54.0

46.6
47.8
65.6
45.0
86.7
56.6

<0.001
not significant
not significant<0.001
not significant<0.05

Table 3. Japanese who received travel vaccines (1998 to 2001)
Hepatitis A
Hepatitis B

1998 (%)
31.0
24.9

1999 (%)
35.0
28.3

2000 (%)
36.3
29.3

2001 (%)
40.3
34.4

P value (1998 vs 2001)<0.001<0.001

Tetanus
RabiesYellow fever
Japanese encephalitis
Cholera

29.8
11.9
7.7
5.4
4.6

34.1
16.5
7.9
8.9
3.4

33.9
16.5
8.4
9.1
2.7

38.0
18.2
9.5
10.5
2.1

<0.001<0.001<0.05<0.001<0.001

Typhoid fever
Meningococcal meningitis

0.9
2.0

1.5
1.2

2.4
1.1

3.6
1.9

<0.001
not significant

２０１Table 4. Comparison of vaccine type received by area in 1998 and 2001

47.8
52.9

The Middle
East
19.7
30.0＊＊＊

Tropical
Africa
46.9
53.9

Latin
America
30.4
42.7＊＊＊

Hepatitis A

1998 21.5
2001 40.1＊＊＊

South East
Asia
32.0
37.2＊

Hepatitis B

1998 17.1
2001 32.5＊＊＊

29.3
32.7

37.1
43.4＊

12.2
22.7＊＊＊

40.8
50.6

18.9
26.2＊

1998
2001
1998
2001
1998
2001

26.2
33.1＊
8.4
15.9＊＊＊
0.3
0.2

52.0
54.8
29.6
37.3＊
1.8
3.2

21.2
34.2＊＊＊
4.5
10.9＊＊＊
3.7
4.4

57.7
54.4
34.2
35.6
79.1
81.1

34.5
44.8**
9.9
18.9＊＊
15.2
25.9＊＊

0.9
1.0
1.3
1.0
0.0
0.9＊
1.3
2.2

1.0
1.1
14.8
4.4＊＊＊
4.6
16.7＊＊＊
25.0
20.6

0.9
1.4
2.5
1.7
0.3
1.0
0.3
0.0

East Asia

Tetanus
RabiesYellow fever

12.9
22.5＊＊＊
2.7
3.9
0.0
0.0

South Asia

Japanese
encephalitis

1998 4.4
2001 8.9＊

Cholera1998 2.9
2001 1.0

7.5
14.2＊＊＊
5.6
2.5＊＊＊

Typhoid fever

1998 0.2
2001 0.8

0.3
1.0

11.9
26.5＊＊＊
5.6
3.2
2.8
10.9＊＊＊

Meningococcal
meningitis

1998
2001

0.1
0.0

0.6
0.7

0.2
0.0

P value of 1998 vs 2001: ＊<0.05 ＊＊<0.01 ＊＊＊<0.001

in endemic regions such as East Asia, Southeast Asia, andSouth Asia. In these three areas, the rates showed significant increases from 1998 to 2001.
Vaccination rates for typhoid fever in 1998 were low inall areas, although 2001 saw slight increases to 16.7% in
tropical Africa and 10.9% in South Asia. Vaccination rates
for meningococcal meningitis were very low everywhere
except for tropical Africa. Even in that region, there was no
major change from 1998 to 2001.
In all regions, the vaccination rates for cholera decreased during the periods of this survey.

DISCUSSION
Infectious diseases are a major health issue for overseas tourists and expatriates in developing countries. For
example, Steffen estimated that the infection rate for hepatitis A is 0.2% for people residing in a developing country fora month [1]. In an investigation by Ohara using membersof Japan Overseas Cooperation Volunteers as subjects, thedisease rate for1year reached 3.9% in 1979 [3]. In a subsequent investigation using the same subjects in 1980, the rate
for hepatitis B was 1.09% per year. There have been nocases of rabies among Japanese expatriates since 1970.
However, according to an investigation by Takayama, from1990 to 1996, the number of subjects who visited a metropolitan hospital for post-exposure vaccination of rabies roseto 93 cases [4]. According to a report by the National Institute of Infectious Diseases, 44 cases of typhoid fever and 25
cases of cholera were reported in 2000. There have been noreports of yellow fever among Japanese travelers, but there
have been cases among European and American travelers inendemic regions [5].
Travel vaccines are regarded as an effective means ofpreventing these diseases [6]. For travelers to developing
countries, vaccination for hepatitis A, hepatitis B, tetanus,
rabies, and typhoid fever are strongly recommended. Also,
vaccinations are recommended for yellow fever in tropical
Africa and South America and for Japanese encephalitis in
Asia.
Since we know that the vaccination rate for Japanese
travelers is extremely low [2], we conducted this survey on
Japanese expatriates living in developing countries from1998 to 2001. The results show that the percentage of people receiving one or more types of travel vaccine before departure increased from 45.6% in 1998 to 53.4% in 2001.
The vaccination rates in tropical Africa and South Asia werehigh, but did not increase much from 1998 to 2001. On theother hand, the vaccination rates in East Asia and the Middle East, which had been low in 1998, increased dramatically, reaching over 45% by 2001.
Rates for individual vaccinations of hepatitis A, hepatitis B, and tetanus were high in all regions, while rates foryellow fever and Japanese encephalitis were high only inendemic regions.
During the period of this survey, vaccination rates ofall vaccines excluding cholera and meningococcal meningitis increased. The rates of hepatitis A, hepatitis B, and tetanus dramatically increased in East Asia, the Middle East,and Latin America. The increase in rabies vaccination rate２
０２

was remarkable in Southeast Asia, the Middle East, andLatin America. Rates for yellow fever vaccinations peaked
at 79.1% in tropical Africa in 1998, with almost no change
after that. This is perhaps due to the fact that some of thetropical African countries demanded that travelers submit ayellow fever vaccination certificate [6]. Presently there issome doubt about the effectiveness of the cholera vaccine
used in Japan, so it is possible that this caused the vaccination rates to decrease in all regions [7].
Vaccination rates for typhoid fever and meningococcal
meningitis tended to be low on the whole. This was because these vaccines were not available in Japan [8]. But in
2001, the vaccination rate for typhoid fever in South Asia
(10.9%) and tropical Africa (16.7%), and the rate for meningococcal meningitis in tropical Africa (20.6%) werehigher than those in another areas. We assume that Japanese people living in highly endemic regions were able tofind a way to receive vaccinations. For vaccines not marketed in Japan, it is still possible to receive a vaccination if
a doctor privately imports the vaccines. We need to makethis fact better known to Japanese medical personnel.
Looking at the overall picture, the increasing rates indicate a growing awareness among Japanese expatriates andmedical personnel of the benefits of vaccination. However,nearly half of Japanese people residing in developing countries are not vaccinated. For short-term visitors, the vaccination rate is probably even lower. In a recent investigation
by Kikuchi, which surveyed a Japanese tourist group visiting tropical Africa, the vaccination rate for yellow fever washigh at 80% [9]. However, the rates of other vaccines suchas hepatitis A and rabies were below 5%. An investigation
on German tourists receiving hepatitis vaccine before going
to developing countries showed a very high rate of 59%[10].
In summary, it is clear that despite some improvement,
vaccination rates are still alarmingly low among Japanese
travelers. The solution to this problem is better educationand knowledge transfer, both to the travelers who should receive these vaccines, and to the medical personnel who con-sult with travelers and administer vaccinations.

ACKNOWLEDGMENT
This study was supported by “The Study on HealthManagement and Disease Prevention for International Travelers” in International Cooperation Research Grant on 2003.

REFERENCES
１）Steffen R, Rickenbach M, Wilhelm U, Helminger A,
Schar M. Health problems after travel to developing
countries. J Infect Dis. 1987; 156: 84-91
２）Basnyat B, Pokhrel G, Cohen Y. The Japanese need travel
vaccinations. J Travel Med. 2000; 7: 37
３）Ohara H, Ebisawa I, Naruto H. Prophylaxis of acute viral
hepatitis by serum globulin, hepatitis B vaccine, andhealth education; A sixteen study of Japan Overseas Cooperation Volunteers. Am J Trop Med Hyg. 1997; 56:
76-79
４）Takayama N. Types of rabies vaccines which were locally injected to the subjects bitten by animals abroad (inJapanese). J J A Inf D. 1997; 71: 751-755
５）Centers for Disease Control and Prevention. Fatal yellow
fever in a traveler returning from Venezuela. MMWR.
1999; 49: 303-305
６）World Health Organization. Vaccine-preventable diseases, vaccines and vaccination. In: WHO edit. International travel and health. Geneva: WHO; 2003 p85-129.
７）World Health Organization. Cholera vaccines; WHO position paper. Wkly Epidemiol Rec. 2001; 76: 117-124
８）Hamada A, Ujita Y, Okuzawa E. Travel vaccines not marketed in Japan (in Japanese). Progress in Medicine.
2001; 21: 540-544
９）Kikuchi H, Hitani A, Arai Y, Sano T, Yokota T, Tanaka Y.
Preventive behavior and morbidity of Japanese tourists
for Africa. Jpn J Trop Med Hyg. 2003; 31: 36
１０）Schunk M, Wachinger W, Nothdurft D.D. Vaccination
status and prophylactic measure of travelers from Germany to subtropical and tropical areas: results of an airport survey. J Travel Med. 2001; 8: 260-262

Tropical Medicine and Health Vol. 32 No. 2, 2004, pp. 203-204
Copyright! 2004 by The Japanese Society of Tropical Medicine

２０３

DETECTION RATES OF ROTAVIRUS ANTIGEN
FROM DIARRHEAL PATIENTS IN LAO PEOPLE’S
DEMOCRATIC REPUBLICBOUNNANH PHANTOUAMATH１, NOIKASEUMSY SITHIVONG１, LAY SISAVATH１, KHAMPHYEU MOUNNALATH１,
KHAMPHENG CHOMLASAK１, SITHAT INSISIENGMAY１, TETSU YAMASHIRO２, and MASAAKI IWANAGA３
Accepted 18, February, 2004

Abstracts: The detection rate of rotaviruses from diarrheal stools in Lao People’s Democratic Republic (Lao PDR)
was studied in the period from 1994 to 2003. Rotavirus antigen was detected using latex agglutination kit. The average detection rate was 2.4%, or 18 of 738 cases examined in total. Rotavirus was not detected from 175 cases examined in 1995, 1998, 2000 and 2003, but 8 of 85 cases (9.4%) examined in 1997 were positive for rotavirus. The
detection rate was 6.0% in the age group younger than 2 years and 0.6% in the age group older than 2 years. These
detection rates were markedly lower than those in neighboring countries such as Vietnam and Thailand.

Rotaviruses are a major cause of diarrhea in infants
and young children. The infections are also common in
adult. Rotavirus infections are frequently seen throughout
the year in tropical areas, but they are predominant during
the winter season in the temperate zone. On the basis of reported data, the detection rate of rotavirus from pediatric diarrhea is about 30% on average〔1-11〕. A high frequencyof rotavirus infection has been reported in Vietnam andThailand, countries neighboring Lao PDR. Some reports
show that the detection rate of rotavirus in pediatric diarrhea
was 50 to 60% in Vietnam and 30 to 40% in Thailand〔3,7,8〕. Although available from many other countries, nodata on the detection frequency of rotavirus from diarrheal
stools has been reported from Lao PDR. In the present paper, therefore, we present the detection rate of rotavirus
from the stools of diarrheal patients in Lao PDR over the
past decade.
Stool samples submitted to our Laboratory (Center for
Laboratory and Epidemiology, Ministry of Health, Lao
PDR) for analysis of enteropathogens from a number ofhospitals and clinics in Vientiane were examined. The samples were collected from diarrheal patients in the period
from 1994 to 2003. All samples were taken in plastic containers, and a total of 738 stool samples were examined.
Rotavirus was detected using a commercially available latex
agglutination kit (MICROGEN, Bioproducts LTD., England
UK). Watery stools were directly treated with an equal volume of extraction buffer included in the kit. Muddy stools
were first diluted double with normal saline solution and100 µl of the diluent was treated with 100 µl of extraction
buffer. The treated samples were centrifuged at 10,000 rpm
for 5 min. A drop of the sensitized latex solution was placed
at 3 places on the special sheet (black background) for the
agglutination test. A drop of positive and negative control
solution was added to the first and second latex, respectively, and a drop of stool supernatant was added to the third
latex. Each sample was mixed well using a toothpick andthen gently tilted several times. Agglutination was visuallyobserved.
The detection rate of rotavirus from diarrheal stools
was generally very low. Only 18 of 738 cases examinedover the past 10 years were positive for rotavirus (2.4%).
No positive case was found among the 175 cases examinedin 1995, 1998, 2000 and 2003. The highest positive rate wasobserved in the 1997 samples, but this was still lower than
10% (Table 1). Rotavirus was mainly detected in theyounger age group, a finding consistent with other reports.
In the age group younger than 2 years, 15 of 250 cases examined (6.0%) were positive, but in age group older than 2
years, the positive rate was 0.6%, or 3 of 488, which was
one-tenth that of the former group (Table 2). In spite of thisfact, high infection rates such as 30 to 60% of pediatric diarrhea were reported in Vietnam and Thailand 〔3,7,8〕
countries neighboring Lao PDR. Although the reason forthe low infection rate in Lao PDR is unclear, population
density, which is markedly lower in Lao PDR than Vietnam
and Thailand, may influence the infection rate. If person toperson infection is the main infection route of rotavirus,

1) Center for Laboratory and Epidemiology, Ministry of Health, Vientiane, Lao PDR
2) Department of Social and Environmental Medicine, Institute of Scientific Research, Oita University, Oita, Japan
3) Division of Bacterial Pathogenesis, Department of Microbiology, Graduated School of Medicine, University of the Ryukyus, Okinawa, Japan２
０
４
Table 1. Detection rate by year
Year
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Total

No. examined
84
67
113
85
24
32
21
84
165
63
738

No. positive (%)
1 (1.1)0
2 (1.8)8 (9.4)0
1 (3.1)0
1 (1.1)5 (3.0)018 (2.4)

Table 2. Distribution by age groupAge group (year)
1>
1-2
2-5
5-15
15<
Total

No. examined
143
107
59
42
387
738

No. positive (%)
9 (6.2)6 (5.6)0
1 (2.3)2 (0.5)18(2.4)

population density may play an important role in the
spreading of the disease. According to a report in 1994〔4〕,rotavirus infection rate among children was 0.96% (16 of
1,668) in New Caledonia where the population density islower than in Lao PDR. The detection method used in thepresent study may also have contributed to the low detection rate. A comparative study on the ability of commercially available ELISA kits and RPLA kits to detect rotavirus in stools revealed that the sensitivity was about 88% in
ELISA and 70% in RPLA〔12〕. The studies in Thailand
and Vietnam used ELISA while the present study in Lao
PDR used RPLA to detect rotavirus. Most samples in thepresent study were collected in the dry season, and there
seems to be some seasonal variation on the detection rate.
Rotavirus is antigenicaly classified into 5 groups, A to E.
These groups have independent RNA. Type A rotavirus is
the most prevalent in humans throughout the world, but infections with type B and C have also been reported〔9,10〕.
Therefore, non-type A rotavirus should also be consideredwhen discussing the infections in Lao PDR.
The present paper briefly reported the distribution ofrotavirus in Lao PDR summarizing the accumulated laboratory data. Since the epidemiological information from thiscountry has been very limited, the data will contribute to
discussions on the worldwide epidemiology of rotavirus infection.

REFERENCE:
１．Albert MJ, Faruque ASG, Faruque SM, Sack RB, and Maharanabis D. Case-control study of enteropathogens associated with childhood diarrhea in Dhaka, Bangladesh. J Clin
Microbiol 1999; 37: 3459-64
２． Bol K, Castagnaro N, Borsa A, Espul C, Fay O, Fabri A,
Grinstein S, Miceli I, Matson DO, and Gomez JA. Surveillance for rotavirus in Argentina. J Med Virol 2001; 65: 190-8
３．Echeverria P, Hoge CW, Dodhidatta L, Tungtaem C,
Herrmann J, Imlarp S, and Tamura K. Etiology of diarrhea
in a rural community in western Thailand: importance ofenteric viruses and enterovirulent Escherichia coli. J Infect
Dis 1994; 169: 916-9
４．Germani Y, Morillon M, Begaud E, Dubourdieu H, Costa R,
and Thevenon J. Two-year study of endemic enteric pathogens associated with acute diarrhea in New Caledonia. J
Clin Microbiol 1994; 32: 1532-6
５．Iwanaga M, Nakasone N, Nakamura S, Wasito EB,
Soeparto P, Sudarmo SM, Soewandojo E, and Ranuh IGNG.
Etiologic agent of diarrheal diseases in Surabaya, Indonesia.
Jpn J Trop Med Hyg 1993; 21: 143-7
６．Kim KH, Shu IS, Kim JM, Kim CW, and Cho YJ. Etiology
of childhood diarrhea in Korea. J Clin Microbiol 1989; 27:1192-6
７．Nguyen THT, Nga TH, Van TT. Rotavirus surveillance inchildren with acute diarrhea in Vietnam. In Proceeding, International Seminar on emerging and re-emerging infectious diseases. 2000; November 16-18, Institute of Tropical
Medicine, Nagasaki University, Japan
８．Pipittajan P, Kasempimolporn S, Ikegami N, Akatani K,
Wasi C, and Sinarachatanant P. Molecular epidemiology ofrotaviruses associated with pediatric diarrhea in Bangkok,
Thailand. J Clin Microbiol 1991; 29: 617-24
９．Sanchez-Fauquier A, Roman E, Colomina J, Wilhelmi I,
Glass RI, and Jiang B. First detection of group C rotavirus
in children with acute diarrhea in Spain. Arch Virol 2003;
148: 399-404
１０．Sanekata T, Ahmed MU, Kader A, Taniguchi K, Kobayashi
N. Human group B rotavirus infections cause severe diarrhea in children and adults in Bangladesh. J Clin Microbiol
2003; 41: 2187-90
１１．Scaletsky ICA, Fabbricotti SH, Carvalho LB, Nunes CR.
Maranhao HS, Morais MB, and Fagundes-Neto U. Diffusely adherent Escherichia coli as a cause of acute diarrhea in young children in Northern Brazil: a case-control
study. J Clin Microbiol 2002; 40: 645-8
１２．Gilchrist MJ, Bretl TS, Moultney K, Knowlton DR, andWard RL. Comparison of seven kits for detection of rotavirus in fecal specimens with a sensitive specific enzyme immunoassay. Diagn Microbiol Infect Dis 1987; 8: 221-8

Tropical Medicine and Health Vol. 32 No. 2, 2004, pp. 205-229
Copyright! 2004 by The Japanese Society of Tropical Medicine

２
０
５

第４
４回日本熱帯医学会 第１８回日本国際保健医療学会 合同大会
シンポジウム３ 「熱帯感染症の臨床：途上国の実態と輸入感染症の動向」報告
日時：２
０
０３年１
０月１１日（土）１５：１
５〜１７：００
会場：北九州国際会議場

国際会議室

わが国における輸入感染症としての熱帯病
増田

剛太，大石

和徳

タイ国北部地域における HIV 陽性患者に合併した市中呼吸器感染症の臨床的検討
麻生憲史

ラオス村落住民におけるタイ肝吸虫の頻度と超音波肝胆道所見
新里敬，Bouakham Vanachone，Chantavilay，Rattanavong，仲宗根啓樹，宮城
わが国におけるマラリア患者の動向
中村哲也

デング熱の臨床と診断
吉田邦仁子
旅行者下痢症−横浜市立市民病院の症例を中心に−
足立拓也

輸入感染症患者に対する臨床現場での初期対応
岩"惠美子

啓，小林

潤

２
０
７

わが国における輸入感染症としての熱帯病
増田

剛太，

大石

和徳

東京都立北療育医療センタ−，長崎大学熱帯医学研究所感染症予防治療分野◆日本の国際化と海外旅行者数の増加
第二次世界大戦敗戦後の混乱期にはわが国にも様々な伝染性疾患（赤痢や腸チフス・パラチフスなどの腸管疾患。
結核，ジフテリア，痘瘡，マラリア，日本脳炎など）が流行した。しかし，１
９
５
５年の国連加盟，さらに，１９６
４年の東京オリンピックを契機として，日本におけるその発生数は著しく減少し，今日に至っている。伝染性疾患減少の要因
としては上下水道の整備や病原体媒介動物の制御などを初めとする衛生環境改善，各種ワクチンや抗菌薬による感染症予防・治療手段の進歩，伝染病予防法などによる防疫業
務の遂行などが挙げられる。これに加え，日本が四面を海に囲まれた島国であり，従来は，これらの疾患がわが国へ簡単に侵入できなかったことが国内の感染症激減に大きな意味を持った。しかし，日本国内からこれらの伝染性疾患（その多くは今日では熱帯地方に常在する）が姿を消した
ことは，その後のわが国に「国内は清潔で安全であり，熱帯病や伝染性疾患は存在しない」という認識が定着する結果を招いた。

◆国際化の進行

日本人の海外旅行ブームの基礎を築いた。さらに，１９７０年に始まったジャンボジェット機航空網の整備は大量の旅行
客を短時間内に遠隔地へ運搬することを可能にした。１９８０
年以降にも日本人海外旅行者数は増加を続け，１
９
９
０年に年
間１
０
０
０万人の大台を突破してからもなお増加し，２
０
０
２年に
は１
６
５
０余万人となった（図１）。その大部分は短期間旅行者であり，彼らは短期旅行後に帰国（再入国）する。他方，外国人入国者（来航者）数も増加しており，２
０
０
２年には５
７
０
余万人を数えた（図１）。すなわち，この１年間だけでも
２２
２０余万人のわが国への入国者（リピーターを含む延べ数）が存在したわけである。これらのうち熱帯地方（発展途上国）への旅行者が占める割合は必ずしも明かではないが，数百万人規模になると考えられ，これらの人々は来航地で流行している疾患を輸入感染症として日本国内に持ち込む可能性がある。島国であるわが国がジャンボジェット機の登場により，機能的にはこれら地域と陸続きになってしまったとも解釈できる。
WHO によれば発展途上国（熱帯地方）への旅行で最も高頻度に遭遇する感染症は旅行者下痢症であるが，さらにマラリア，腸チフス，ウイルス性出血熱や各種寄生虫性病などの今日のわが国に流行していない伝染性疾患が常在する地域がある。

その後も日本は経済大国化への道を直進し，１
９
６
６年度には国民総生産（GNP）が世界第３位となり，昨今見られる図１.日本人海外旅行者数・外国人日本入国者数の経年変化

２０８
表１．渡航地・来航地別にみた２０００年の流行感染症と出国日本人数・正規入国外国人数
渡航地／来航地

出国日本人数＊１）
１
７,８
１
８,５
９
０人

アジア（東アジア，東南
アジア，中南アジア，西
アジア）

８,４
８
１,４
７
２人

感

染

症＊２）

３,２
２
２,９８
２人

マラリア，腎症候性出血熱，デング熱，日本脳炎，Ａ型肝炎，Ｂ型肝炎，Ｅ型肝炎，メリオイドーシス，レプトスピラ症，ペスト，ブルセ
ラ症，髄膜炎菌性髄膜炎，ツツガムシ病，コレラ，ポリオ，細菌性赤痢，その他細菌性下痢症，腸チフス，パラチフス，ランブル鞭毛虫症，
赤痢アメーバ感染症，クリミア・コンゴ出血熱，リーシュマニア症（皮膚，内臓），オンコセルカ症，AIDS，狂犬病，各種寄生虫症

北アメリカ

５,５
１
９,６
５
２人

８９０,７
７
１人

サルモネラなどによる細菌性下痢症，ライム病，ロッキー山脈紅斑熱，ハンタウイルス肺症候群，デング熱，マラリア，リーシュマニア症（皮膚，皮膚・粘膜），腸チフス，パラチフス，ブルセラ症，赤痢アメー
バ感染症，細菌性赤痢，AIDS，狂犬病，西ナイル熱

ヨーロッパ

２,３
７
４,８
４
５人

８
１４,９１２人

サルモネラ症，カンピロバクター腸炎，ジフテリア，AIDS，ライム病，Ａ型肝炎，狂犬病

オセアニア

１,２６
７,４
９
２人

１
８４,９７４人

デング熱，マラリア，腸チフス，Ａ型肝炎，細菌性下痢症，フィラリア症，AIDS２０,６
４
３人

マラリア（特にサハラ以南），フィラリア症，回帰熱，リーシュマニ
ア症（皮膚，内臓），トリパノソーマ症（睡眠病），ペスト，ラッサ熱，
エボラ出血熱，クリミア・コンゴ出血熱，マールブルグ出血熱，リフトバレー出血熱，西ナイル熱，黄熱，メジナ条虫症，髄膜炎菌性髄膜炎，ブルセラ症，住血吸虫症（ビルハルツ），細菌性赤痢，コレラ，
その他感染性下痢症，赤痢アメーバ感染症，ランブル鞭毛虫症，A 型
肝炎，Ｅ型肝炎，腸チフス，狂犬病，蠕虫症，AIDS，狂犬病

６
８,４
２
０人

１３
５,７
７
０人

マラリア，アメリカトリパノソーマ症（シャガス病），リーシュマニア症（皮膚，皮膚・粘膜），ペスト，黄熱，デング熱，腸チフス，パラチフス，Ａ型肝炎，Ｂ型肝炎，赤痢アメーバ感染症，コレラ，住血吸虫症（ビルハルツ），髄膜炎菌性髄膜炎，AIDS，狂犬病

２
３
９人

２,０４
３人

アフリカ

１０
６,４
７
０人

南アメリカ

その他・無国籍＊

正規入国外国人数
５,２
７
２,０
９５人

１）入国日本人数１
７，
６
５
５，
９
４
６人

＊

２）下線は発熱を主症状とする疾患◆渡航地・来航地別にみた流行感染症と出国日本人数・正規入国外国人数
２
０
０
０年の出国日本 人 数・正 規 入 国 外 国 人 数 を 大 陸 別（WHO による）に分け，各大陸で流行している特異的な感染症と対比した資料を示す（表１）。日本人出帰国記録
は２
０
０
１年７月以降分が廃止された。従って，日本人旅行者の旅行地別集計はここに示した２０
００年が最後の成績になる。
日本人の渡航地で最も多いのはアジアで８４０余万人，来航
外国人数も３２０余万人であり，合計１１
６０余万人がアジア地域から日本に入国したことになる。アジアはきわめて範囲が広く，地域により事情がかなり異なるが，さまざまな熱
帯病や伝染性疾患の侵淫地が散在する。アフリカや南アメ
リカなどのマラリアや各種ウイルス性出血熱などの急性感染症がとくに広く流行している地域への旅行者・来航者は現時点ではそれほど多くないことが分かるが，今後，その動向を知る上でも日本人出帰国記録は不可欠ではないだろうか。
以上にわが国を中心にみて人的交流が盛んになり，それに伴い，来航先で流行している感染症，とくに熱帯病が輸入感染症としてわが国に持ち込まれる可能性が増加していることを示した。今日のわが国ではこれらの疾患に関する認識がきわめて低いために，臨床の場で見逃され，誤診される可能性が高いことが大きな問題点として指摘できる。
今後は，国際化により，多くの熱帯病・伝染性疾患が日本国内に侵入していること，とくにマラリアやチフス性疾患など急変する可能性がある疾患，住血吸虫など慢性に経過する疾患など現在の日本人に余り知られていない疾患に関する国内向けの啓蒙活動，さらに熱帯病の克服に向けた研究事業による国際貢献が重要な課題になる。

２０９

タイ国北部地域における HIV 陽性患者に合併した
市中呼吸器感染症の臨床的検討麻生憲史

長崎大学熱帯医学研究所内科

はじめに
２
０
０
２年末現在の世界の HIV 感染者および AIDS 患者数
は４２
００万人，アジア・太平洋地域にはこのうち７２０万人が存在すると推計されている。そのうちアジアの中で推定
HIV 感染率が１％を超えているのはカンボジア，ミャン
マーおよびタイの３カ国のみである。このうちタイでは政府の政策が功を奏して感染者が減少に転じているものの，年間の新規 AIDS 発生は２万人程度認められ依然重要な問題である。
このような背景のもと，我々はタイ国北部地域におけるHIV 陽性患者に合併した市中呼吸器感染症の病態を明らかにする目的で，１
９
９
６年１
２月より２
０
０
２年１月の間にチェン
マイのナコンピン病院において入院治療を行った HIV 感
染者に合併した市中呼吸器感染症１９１症例１９２エピソードについて起炎病原体と治療法の実態調査および治療効果判定を行なった。とりわけ，Streptococcus pneumoniae と Rhodococcus equi は HIV 陽性患者に合併した市中呼吸器感染症の主要な起炎菌であり，以下の解析を行なった。

!．Streptococcus pneumoniae
１．緒言
肺炎球菌は肺炎のみならず中耳炎，副鼻腔炎，菌血症，髄膜炎の起炎菌として知られている。元来，ペニシリンに高感受性を示していたが，近年ペニシリン耐性肺炎球菌が世界的に広まっており，その耐性はペニシリンのみにとど
まらず，多剤耐性の傾向を認める。タイ国においては１
９
９
２
年から１
９
９
４年にかけての急性呼吸器感染症の小児の鼻咽腔から分離された肺炎球菌の３７．
２％がペニシリン耐性菌であったとの報告があるものの，成人におけるペニシリン耐性肺炎球菌の現状は明らかではない。
２．対象と方法
チェンマイ大学医学部附属病院で，１９９
９年９月から２０００
年６月の間に，９３症例の種々の検体より分離された肺炎球菌９３株について最小発育阻止濃度（以下 MIC）および血清型を測定し，年齢別の耐性化の状況等について検討した。
また，ペニシリン高度耐性菌（PRSP）についてはパルス
フィールド電気泳動法（PFGE）による解析を行い，国際流行株との比較を行った。

３．結果
９
３株中２
９株（３
１．
２％）はペニシリン感受性株（PSSP）
，
２
４株（２
５．
８％）はペニシリン低感受性株（PISP）
，そして
４
０株（４
３．
０％）は PRSP であった。その他の薬剤についてはセフェム，クロラムフェニコール，テトラサイクリン，
マクロライド，アミノグリコシドなどに対し多剤耐性傾向を示したが，カルバペネム，グリコペプチドには感受性を有しており，その薬剤感受性成績はペニシリンの薬剤耐性化がやや高度であることを除けば日本とほぼ同様の傾向であ っ た。年 齢 別 で は，５歳 以 下 に お い て PSSP が３株（２１．
４％）と他の年齢層（３０％〜６０％）に比べて少なく，耐性菌の検出率が高い傾向にあった。血清型の分布は PSSP
では多様性を示したが，PRSP では６B，１
９F，２
３F の３つの血清型で全体の９０％を占めていた。Figure.１に示すように，この３つの血清型を示す PRSP における PFGE の解析
では血清型１９F を示す１
６株中，国際流行株台湾１
９F のサブタイプが２株しか認められず，これとは異なる PFGE 型別を示す群が１
２株と半数以上を占めた。血清型６B では，１１
株全てが同じ型別か，そのサブタイプであった。血清型２３F を示す９株中，７株が国際流行株スペイン２
３F と同じ型
別かサブタイプで，２株がそれとは異なる PFGE 型別を示
１）
した。
４．考案
タイ国北部地域においてもペニシリン耐性肺炎球菌は本邦同様高頻度に認められ，一部の薬剤を除いて多剤耐性傾向が確認された。タイは近年 AIDS 症例の発生数が減少傾向に転じたものの，いまだ世界の中では AIDS 患者が非常に多い地域なので，今後，今回の MIC 成績を基にした治療戦略の見直しに加えて，AIDS 症例などのハイリスク患者においては肺炎球菌ワクチンの検討が望まれる。

"．Rhodococcus equi
１．緒言
Rhodococcus equi は元来，家畜，特に子馬に呼吸器感染症を引き起こす原因菌として知られていた。１
９
６
７年に初め
て人への感染が報告されて以来，日和見感染症の原因菌として認識されてきた。その後１９
８０年代の AIDS の流行により，人においての呼吸器感染症の報告が増加し，既にタイ
国北部地域ではまれな疾患ではなくなっている。R. equiの治療には erythromycin と rifampin（RFP）の併用が推奨されているが，既に RFP 耐性株は少数ではあるが報告さ２
１
０Figure. 1

れている。近年 Fines らは結核菌などと同様に子馬から分離された R. equi において RFP 耐性に関与する rpoB 遺伝
子のアミノ酸変異を報告している。しかし，人由来の耐性株がどのような遺伝子変異を持つのかは解っていない。
２．対象と方法
タイ国北部地域において１
９
９
３年より２
０
０
１年の間に分離された R. equi３０株に対し RFP に対する MIC を測定した。その結果，２６株は MIC １ µg/ml 以下の感受性株であったが，１株は MIC８µg/ml を示す軽度耐性株で，残 り の３株 はMIC６４µg/ml 以上を示す高度耐性株であった。これらの軽度耐性株と高度耐性株は１
９
９
８年から２
０
０
１年の間に分離されたものであり，その耐性株４株と，同時期に分離された
RFP 感受性株４株の合計８株を対象として rpoB 遺伝子のアミノ酸変異とパルスフィールド電気泳動法による分子疫
学的検討を行った。PFGE は菌株を BHI ブロスで３５℃一夜静置培養したものを遠心し，沈渣を PettIV で懸濁。懸濁
液を２％Incert Agarose を用いてブロックとした。ブロッ
ク 内 の R. equi を Lysostaphin で 溶 菌 後，Proteinase K で 蛋
白質を消化した。制限酵素 PshBI で切断後，CHEF Mapper
を用いて電気泳動を行った。泳動時間は２０時間１８分とした。
また，PCR は RFP 耐性に関与する rpoB 遺伝子の増幅を２１１行い，この PCR 産物をオートシークエンサーを用いて塩基配列を決定し，アミノ酸配列に翻訳した。

Table. 1 RFP MICs, RpoB amino acid substitutions, andPFGE patterns of Rhodococcus equi detected fromAIDS patients
Strain
No.
1
2
3
4
5
6
7
8

３．結果
Table.１に 示 す よ う に２株 の 高 度 耐 性 株 は PFGE で A
pattern，DNA sequencing にて５
３１位のセリンがトリプトファ
ンへの変異を示し，１株の高度耐性株は PFGE で B pattern,
DNA sequencing にて５
２
６位のヒスチジンがチロシンへの変異を示し，軽度耐性株は PFGE で C pattern，DNA sequencing にて５０
９位のセリンがプロリンへの変異を認めた。一
方，４株の感受性株は PFGE で耐性株とは違った型別を示
２）
し，rpoB 遺伝子のアミノ酸変異は認めなかった。
４．考案
今回，初めての人由来 RFP 耐性 R. equi の検討で，５２６位のヒスチジンがチロシンへ変異し高度耐性を獲得していることを明らかにした。変異したアミノ酸は異なるものの，この部位の変異は家畜由来の R. equi にても確認されており，やはり RFP へ高度耐性を示していた。また，５
３１位のセリンがトリプトファンへ変異し高度耐性を獲得したが，これも変異したアミノ酸は異なるものの，５
３
１位のセリン
の変異は家畜由来の R. equi にても確認されている。ただし，この場合は軽度耐性を示していた。一方，結核菌においてもこの部位の変異は認められており，その際は高度耐性に関わっていた。そして今回，軽度耐性株において５０
９位のセリンがプロリンへ置換されていたが，この位置の変異は今まで R. equi においての報告はない。以上，我々のRFP MIC(µg/ml)
>128
>128
64
8
0.5
0.5
0.5
0.5

Amino acid substitution(E. coli numbering)
Ser 531 Trp
His 526 Tyr
Ser 531 Trp
Ser 509 Pro
None
None
None
None

PFGE
patterns
A1
B
A2
C
D
D
E1
E2

結果は，タイ国北部地域の AIDS 患者において数タイプのRFP 耐性 R. equi が広まりつつあることを示した。

文

献１）Watanabe, H., N. Asoh, K. Hoshino, et al. 2003. Antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae and molecular characterization ofmultidrug-resistant serotype 19F, 6B, and 23F pneumococciin Northen Thailand. J. Clin. Microbiol. 41: 4178-4183.
２）Asoh, N., H. Watanabe, M. Fines-Guyon, et al. 2003.
Emergence of rifampin-resistant Rhodococcus equi withseveral types of mutations in the rpoB gene among AIDS
patients in Northern Thailand. J. Clin. Microbiol. 41: 23372340.

２１３

ラオス村落住民におけるタイ肝吸虫の頻度と超音波肝胆道所見
新里緒敬１，BOUAKHAM VANACHONE２，CHANTAVILAY RATTANAVONG３，
仲宗根啓樹１，宮城
啓１，小林
潤４

言

タイ肝吸虫（Opisthorchis viverrini）は生魚の摂食により感染し，ヒトの胆管や胆嚢に寄生する。タイ東北部では住民の約６０〜７０％にタイ肝吸虫の感染が認められ，胆管癌との関連も指摘されている（Kullavanijaya et al.,１９９９）。
メコン川を挟んでタイ東北部と国境が接し，生魚の摂食という同じ食習慣を持つラオス人民共和国においても，タ
イ肝吸虫症は公衆衛生上の主要課題の一つである。小林らによるラオス国カムワン県における１
５歳以下の住民の糞便調査では，感染率は３７.５％と報告された（Kobayashi et al.,
１
９
９
５）
。
我々は１
９
９
６〜１
９
９
７年にかけて，ラオス国カムワン県の３つの村で住民の糞便調査を行った。その調査結果（Kobayashi et al., ２０００）の概要を紹介するとともに，O. viverrini
陽性者と陰性者における腹部超音波検査所見の比較検討を行ったので報告する。

対象と方法
１．糞便中のタイ肝吸虫虫卵調査
ラオス国カムワン県で，日本−ラオス国際技術協力公衆衛生プロジェクトの寄生虫コントロールプログラムにおける調査対象地域となっていた３つの村（Sisomsouen, Pha-

Figure 1１vang, Thakhek Neua）の住民を対象とした。Sisomsouen とPhavang は県庁所在地の Thakhek 市から約５５!北に位置する村で，両村とも村の周囲には田園しかない。両村の違い
は，Sisomsouen の約２０％の家にトイレが設置されたが，Phavang には１個もトイレはなかったことである。一方，Thakhek Neua は Thakhek 市の中にあり，経済的にも衛生的にも比較的恵まれた環境にあった。いずれの村民も，生魚をよく摂食する習慣があった。
３つの村民から６
７
１検体（Simomsouen １
８
９，Phavang ２
５
８，Thakhek Neua ２２４）の糞便を回収した（回収率４
４〜７
３％）
。
２．方法
回収された便検体は２日以内に Kato-Katz 厚層塗抹法で検鏡された。感染強度は３３mg の便中に含まれる総虫卵数で表した。
虫卵陽性者で無症状の Thakhek Neua 住民のうち，同意の得られた８４名（男性４
７名，女性３
７名，７〜６
６歳：中央値３７歳）に対し腹部超音波検査を施行し，肝胆道系所見の有無を調べた。また，カムワン県病院を何らかの消化器症状
または腹部痛で受診し，腹部超音波検査の依頼があった患者のうち同意の得られた５３名（男性１
１名，女性４２名，３〜
７
７歳：中央値３６歳）に対して，糞便検査を施行し，タイ肝吸虫の虫卵の有無を調べ，腹部超音波検査の肝胆道系所見と合わせて検討した。腹部超音波検査は，肝胆道系疾患をPrevalence of Opisthorchis infection in 3 villages.

琉球大学大学院医学研究科感染病態制御学講座分子病態感染症学（第一内科），２ Center of Malariology, Parasitology and Entomology(CMPE), Ministry of Health, Lao P.D.R.，３ Khammouane Province Hospital, Lao P.D.R.，４ 琉球大学医学部地域環境医科学講座熱帯寄生虫学分野（現，国立国際医療センター国際協力局派遣協力課）

２
１
４

Ａ

Figure 2

Ｂ

Ultrasonographic hepatobiliary findings in case of Opisthorchis infection: 2-A and 2-B showeddilatation of intrahepatic bile duct (arrow) and intrahepatic enhanced echoes, respectively.

専門とする日本人医師と Khammouane 県病院の腹部超音波検査担当医師により施行された。
検定
データの解析は統計解析ソフト（SPSS）を用いて行った。Ｐ値が０.０５以下を有意差ありとした。

結果

１．タイ肝吸虫保有率
O. viverrini の陽性率は６
７
１名中３
７
５名（５
５.９％）で，うち成人の虫卵陽性者は２
９
４名中２
１
５名（７
３.１％）と高率であった。村 ご と の 陽 性 率 は Simomsouen で５２.９％，Phavang で
５５.０％，Thakhek Neua で６０.７％と，３群間での有意差は認められなかったが，年代別に比較すると，３村とも年齢の増加とともに陽性率が上昇し，１
５歳以上では感染率は５０％を超えていた。特に Thakhek Nuea では１
０歳未満の陽性率が他の２村と比較して高率であった（Figure１）。
２
０歳以上の成人２
９
４名中２
１
５名（７
３.１％）が虫卵陽性で，３
Table 1

Intensity distribution of liver fluke egg counts (EPG,
eggs per gram of feces) of the examied cases over
the age of 20 in 3 villages.

EPG group0
1-1,000
1,000-6,000>6,000Sisomsouen
33(35.1)
49(52.1)
12(12.8)0( 0)Phavang31(24.8)54(43.2)
37(29.6)3( 2.4)

Thakhek Neua
15(20.0)28(37.3)
26(34.7)6( 8.0)The number in parentheses indicates the proportion of the examined cases.

つの村の住民で糞便中のタイ肝吸虫虫卵数（EPG：便１!
当たりの虫卵数）を比較した結果を Table１に示した。成人の虫卵陽性率は Thakhek Neua が多く，また，糞便中の虫卵数も他の２村の住民に比べ多かった。
２．超音波検査結果
腹部超音波検査の肝胆道系所見の結果を虫卵陽性者群と陰性者群，および有症状群（病院受診患者）と無症状群（住民）とに分けて，Table２に示した。虫卵陽性者群では，
虫卵陰性者群に比べ正常所見であった人は少なく，逆に胆管の拡張所見が認められた人が有意に多かった。有症状群と無症状群の比較では，有症状群で正常所見者が少なく，胆管拡張所見の認められた人が多かった。
虫卵陽性者における典型的な腹部超音波所見を Figure２に示した。虫卵陰性者群と比較し，肝内胆管の拡張と胆石・胆泥が有意に認められた。また，
肝実質の粗造と点状エコー像も認められたが，糞便中の虫卵数の多い人で所見が強く出る傾向にあった。
便中の虫卵数と腹部超音波所見との関連を調べたが，虫卵数が多い人（５，０
０
０個／!以上）に胆管拡張や肝実質の変化が多く認められる傾向にあったが，明確な関連は認められなかった。また，有症状群と無症状群間での虫卵数と腹部超音波所見の関連も認められなかった。
腹部超音波検査で診断された疾患は，胆管細胞癌は１例（０.７３％）のみ（タイ肝吸虫虫卵陽性）で，脂肪肝１
８例，
慢性肝炎２例，肝硬変１例，肝細胞癌４例，胆嚢結石９例であった。肝胆道系以外の疾患として，腎結石４例，膀胱
結石１例，膀胱癌１例，卵巣嚢腫３例，子宮筋腫１例が認
められた。

２
１
５

Table 2

Prevalence of ultrasonographic hepatobiliary findings of the group who provided a stool sample and those who were
examined by ultrasound.

Examined group

Ultrasonographic findings

Asymptomatic residents(n=53)

NormalIntrahepatic enhanced echoes
Gall-bladder abnormality
Gall-bladder sludge and stones
Dilatation of intrahepatic bile ducts

Symptomatic patients(n=84)

NormalIntrahepatic enhanced echoes
Gall-bladder abnormality
Gall-bladder sludge and stones
Dilatation of intrahepatic bile ducts

Egg positive (91 cases)
Mean egg countNumber of cases(per1gram feces)
20 (54.1)＊
1721
9 (24.3)
1986
1 (2.7)333
3 (8.1)1526
12 (32.4)†
1315
17 (31.5)†‡
18 (33.3)
1 (1.9)6 (11.1)†
28 (51.9)†‡

Egg negative (46 cases)
Number of cases
11 (68.8)
4 (25.0)0 ( 0)
2 (12.5)0 ( 0)

3456
3698
3666
1030
2808

18 (60.0)
8 (26.7)
1 ( 3.3)0 ( 0)
7 (23.3)

The number in parentheses indicates the proportion of the findings that was detected by ultrasound examination.
＊p<0.005 and †p<0.001, compared to egg negative group; ‡p<0.001, compared to asymptomatic group

考察

本研究の結果により，隣国のタイの住民同様に，ラオス
人民共和国の住民ではタイ肝吸虫の感染率が高いことが示された。タイの村落における同様の調査結果では，子供の感染率が１０％未満で年齢とともに次第に微増していくのに対し（Brockelman et al.,１
９
８
７: Kurathong et al.,１
９
８
７: Haswell-Elkins et al., １
９９１），今回のラオスでの調査では，子供の感染率が２０％以上と高く，その感染率は年齢とともに急増
し，１５歳以上で５０％を超える結果となった。Kobayashi らが以前に行った別の村の糞便調査でも子供の感染率は同様の結果であったことから（Kobayashi et al., １
９
９
６）
，ラオス
の乳幼児期から生魚を摂食するという習慣がタイ肝吸虫の感染率に大きく関わっているものと考えられた。３つの村のうち，都市部の村である Thakhek Neua での陽性率が高かったのは興味深いが，これは他の村落では平地ラオ族と中地ラオ族の混合によってなっているが，この村落は大部分が平地ラオ族のみで形成されていることが影響しているかもしれない。ラオスは多くの民族から形成されているが，大きく平地，中地，高地ラオ族に分けられる。魚の生食は
平地ラオ族に多いといわれており，ラオス保健省の調査やRim らによれば，高地ラオ族や中地ラオ族の多い県では感染率は少ない（Rim et al.,２００３）。
ラオスの住民は乳幼児期からタイ肝吸虫の感染に曝されていることから，肝胆道系疾患のリスクが大きいと考えられる。タイ肝吸虫症は疫学的にも実験的にも胆管癌との強い関連性が指摘されている（Watanapa and Watanapa, ２００２:Kullabanijaya et al.,１９９９）。今回の調査では，超音波検査を施行した１
３
７例中１例（０.７３％）で胆管細胞癌が見つかった。この頻度はタイ東北部における同様な調査結果とほぼ近いが（Haswell-Elkins et al., １９９４），今回の検討における超音波検査施行症例数は比較的少なく，今後症例数を増やしての検討が望まれる。
タイ肝吸虫症の腹部超音波所見に関しては，肝左葉の大きさの増大，胆嚢壁の不明瞭化，胆嚢内胆泥，胆石，肝実質の粗造と点状エコー像，肝内胆管拡張などの所見が，特に重感染者で顕著に認められると言われている（Mairiang
et al.,１９９
２）。今回の我々の検討でも，肝実質の粗造と点状エコー像に加え，虫卵陽性者では特に肝内胆管の拡張と胆石・胆泥が多く認められ，糞便中の虫卵数が多い症例ほど
超音波検査所見も強い傾向にあった。
以上の結果より，タイ肝吸虫はラオス住民の間に乳幼児期より高頻度に感染しており，腹部超音波検査結果と合わせて考えると，タイ肝吸虫症は比較的中等度から重篤な肝胆道疾患との関連性があることが示唆された。タイ肝吸虫症のコントロールには，生魚の摂食を避けるという公衆衛生の教育と啓蒙が重要であるとともに，ラオスにおいても胆管細胞癌などの重篤な肝胆道系疾患の早期診断と治療に関する対策が今後重要となってくると思われる。

謝辞

この研究は，国際協力事業団の日本-ラオス公衆衛生プ
ロジェクトの支援を受けてなされたものである。この研究の意義を理解し，多大なる御協力をいただいたラオス人民共和国の保健省および CMPE のスタッフに深謝いたします。また，惜しみない協力と力添えをいただいたカムワン
県衛生局，県病院，および Hinboon 郡と Thakhek 郡衛生局のスタッフに心から感謝いたします。さらに，研究方法やデータ解析の御指導をいただいた琉球大学大学院医学研究
科感染病態制御学講座分子病態感染症学分野（第一内科）の佐久川廣先生，斎藤厚教授，および医学部地域環境医科学講座熱帯寄生虫学講座の佐藤良也教授に深謝いたします。

文献１）Brockelman, W.Y., Upatham, E.S., Viyanant, V., and Hirunraks, A. (1987): Measurement of incidence of the hu-

２１
６

man liver fluke, Opisthorchis viverrini, in northeast Thailand. Trans. R. Soc. Trop. Med. Hyg., 81: 327-335.
２）Haswell-Elkins, M.R., Elkins, D.B., Sithithaworn, P.,
Treesarawat, P., and Kaewkes, S. (1991): Distribution pattern of Opisthorchis viverrini within a human community.
Parasitology, 103: 97-101.
３）Haswell-Elkins, M.R., Mairiang, E., Mairiang, P., Chaiyakum, J., Chamadol, N., Loapaiboon, V., Sithithaworn,P., and Elkins, D.B. (1994): Cross-sectional study ofOpisthorchis viverrini infection and cholangiocarcinoma
in communities within a high-risk area in northeast Thailand. Int J Cancer. 59: 505-9.
４）Kobayashi, J., Vannachone, B., Xeutvongsa, A., Manivang,
K., Ogawa, S., Sato, Y., and Pholsena, K. (1996): Prevalence of intestinal parasitic infection among children in
two villages in Lao. P.D.R. Southeast Asian J. Trop. Med.
Public Health, 27, 562-565
５）Kobayashi, J., Vannachone, B., Sato, Y., Manivong, K.,
Nambanya, S., and Inthakone, S. (2000): An epidemiological study on Opisthorchis viverrini infection in Lao
Villages. Southeast Asian J. Trop. Med. Public Health, 31,
128-132
６）Kullavanijaya P., Tangkijvanich, P.T., and Poovorawan, Y.

(1999): Current status of infection-relatd gastrointestinal
and hepatobiliary diseases in Thailand. Southeast Asian J.
Trop. Med. Public Health, 30: 96-105.
７）Kurathong, S., Lerdverasirikul, P., Wongpaitoon, V., Pramoolsinsap, C., and Upatham, E.S. (1987): Opisthorchis
viverrini infection in rural and urban communities innortheast Thailand. Trans. R. Soc. Trop. Med. Hyg., 81:
411-414.
８）Mairiang, E., Elkins, D.B., Mairiang, P., Chaiyakum, J.,
Chamadol, N., Loapaiboon, V., Posri, S., Sithithaworn, P.,
and Haswell-Elkins, M. (1992): Relationship between intensity of Opisthorchis viverrini infection and hepatobiliary disease detected by ultrasonography. J. Gastroenterol.
Hepatol. 7: 17-21.
９）Rim, H.J., Chai, J.Y., Min, D.Y., Cho, S.Y., Eom, K.S.,
Hong, S.J., Sohn, W.M., Yong, T.S., Deodato, G., Standgaard, H., Phommasack, B., Yun, C.H., Hoang, E.H.
(2003): Prevalence of intestinal parasite infections on anational scale among primary schoolchildren in Laos.
Parasitol. Res. 91: 267-272.
１０）Watanapa, P., and Watanapa, W.B. (2002): Liver flukeassociated cholangiocarcinoma. Br. J. Surg., 89: 962-970.

PREVALENCE AND ULTRASONOGRAPHIC HEPATOBILIARY
FINDINGS OF LIVER FLUKE, OPISTHORCHIS VIVERRINI, IN LAO VILLAGESTAKASHI SHINZATO１, BOUAKHAM VANACHONE２, CHANTAVILAY RATTANAVONG３,
HIROKI NAKASONE１, KEI MIYAGI１, JUN KOBAYASHI４

Abstract: Infection with the liver fluke, Opisthorchis viverrini, remains a major public health problem in Lao P.D.
R. Cholangiocarcinoma caused by the liver fluke is the most common form of liver cancer in Northeast Thailand
where an about 60 to 70% of the population are infected with the fluke. The parasite is also common to the lowlands of Lao among people with close ethnic ties to northeast Thai, but the prevalence and incidence of the infection in Lao are still not uncertain. The objective of our report is to investigate the prevalence of chronic infection
with O. viverrini and to identify chlanginocarcinoma within a population-based survey of the infection in Lao.
Stool samples from 670 residents (0-87 y.o) from 3 villages in Khammouane Province were examined for intensityof liver fluke infection. People from varying egg count categories were selected for ultrasound examination to identify hepatobliary disease. Patients coming to provincial hospital with abdominal symptoms were examined in thesame way as the residents were done. The rate of the parasite was 56% among the residents and reached up to 73%
in age group greater than 20 years old. The parasite was found even in 20% of age group below 5 years. Only one
subclinical case of cholangiocarcinoma were diagnosed among 137 people, based on ultrasonographic evidence.
Dilatation of intrahepatic bile ducts and Gall-bladder sludge and stones were observed higher within the moderate
and heavy liver fluke-infected group. This survey suggests prevalence of the liver fluke is higher than previously
thought, and that the intensity of the parasite might be related with the formation of hepatobiliary lesion. although
it could not elucidate the relation with cholangiocarcinoma.
１

Division of Infectious Diseases, Department of Internal Medicine, Graduate School and Faculty of Medicine, University of the Ryukyus, Japan,
Center of Malariology, Parasitology and Entomology (CMPE), Ministry of Health, Lao P.D.R., ３Khammouane Province Hospital, Lao P.D.R.,
and ４Division of Tropical Parasitology, Department of Social and Environmental Medicine, Faculty of Medicine, University of the Ryukyus (Current address: Expert Service Division, Bureau of International Cooperation, International Medical Center of Japan)

２

２
１
７

わが国におけるマラリア患者の動向中村哲也

東京大学医科学研究所附属病院感染免疫内科

１．はじめにわが国におけるマラリア患者のほとんどは海外で感染したいわゆる輸入症例である。例外として，航空機により国内に持ち込まれた感染蚊から感染したと思われる「空港マラリア」がまれに報告されている。マラリア患者数の動向

は，感染症法（旧伝染病予防法）に基づく届出と，各施設の報告またはアンケートによる全国集計から推測するとができる。後者に関する過去の主な報告を表１にあげた（１-８）
。本稿では，表１のうち主に木村らの報告と東京大学
医科学研究所附属病院での集計結果をあわせ，わが国におけるマラリア患者の動向を解析する。

表１ わが国のマラリア患者動向の報告
発表年

発表者（文献）

１９
９２
１９
９３

調査対象

調査時期

調査期間

症例数

症例／年

大友弘士! 全国集計

最近２
０年間

２
０年

１
６
７
８例

８
４人

大友弘士" 全国集計

１
９
８８-１
９９
２

５年

４２３例

８
５人

１９
９４

増田剛太# 東京都立駒込病院

１
９
７５-１
９９
２

１８年

１
０９

６人

１９
９６

大西健二$ 東京都立墨東病院

１
９
８７-１
９９
５

９年

３４

４人

２０
０１

大友弘士% 全国集計

１
９
９９-２
００
０

２年

２２６

１
１
３人

２０
０１

増田剛太& 東京都立駒込病院

１
９
７５-２
００
０

２５年

２
７４

１
１人

２０
０２

三浦聡之' 東京大学医科学研究所附属病院

１
９
９２-２
００
１

１０年

１
７０

１
７人

２０
０３

木村幹男( 全国集計

１
９
９０-２
００
０

１１年

１
２
５
３

１１
４人

２．総患者数４．治療と予防

感染症法（旧伝染病予防法）に基づく届出状況によれば，
我が国におけるマラリア患者数は１９９８年までは年間６０人前後であったが，その後１
４０人前後に増加している（図１参照）（９）。一方，大友らによる全国調査では，法規に基づく届出数よりも多くの患者数が報告され，年間１２０名程度である（８）。したがって，最近の法規に基づく届出数の増加傾向は感染症法の施行に伴う届出頻度の増加の影響が大きいと推測される。東京大学医科学研究所附属病院の集計では，各年度ごとにばらつきはあるがおおむね１０〜２０名のマラリア患者が受診している（図１）（８）。これらの結果を総合すると，わが国におけるマラリア患者数は年間１２０〜１４０人でほぼ一定しているのではないかと思われる。

東京大学医科学研究所附属病院では，原則として熱帯熱マラリアに対してはメフロキンで，非熱帯熱マラリアに対してはクロロキンで治療を行っている。したがって，使用頻度は原虫種頻度に比例し，約５０％がメフロキン，約４０％がクロロキンを投与されている。予防薬としてメフロキンが２００１年に認可されて以来，東京大学医科学研究所附属病院では，年間約３０人にマラリア予防用のメフロキンを処方している。

３．推定感染地域および原虫種
推定感染地域は，木村らの全国集計（１
９
９
０-２
０
０
０年）に
よればアフリカとアジアがそれぞれ約４０％で，残りがオセ
アニア，中米となっている。東京大学医科学研究所附属病院での過去１
０年間（１
９
９
２-２
０
０
１）の集計では，アフリカが約６０％，アジアが約３０％と全国集計に比べアフリカが多い傾向にあった。原虫種は，アフリカでの感染の９０％以上が熱帯熱マラリアで，それ以外の地域では２／３以上が三日
熱マラリアであった。マラリア患者全体に閉める熱帯熱マ
ラリアの頻度は，経時的にやや増加している傾向にあった。

５．死亡率
わが国の１
９
９
０年から２
０
０
０年までのマラリア患者１
２
５
３名中，
死亡例が１
６名あり死亡率は１．
３％であった。これは，欧米での死亡率の報告（英国：７
８
０
１名中５
１名，０．
６
５％，ドイツ：
３
７
４
７名中１
３
５名，３．
６
０％）に比べほぼ同等の数字である（１０）
。

６．わが国におけるマラリア治療および予防の問題点
わが国で抗マラリア薬として認可されている薬剤は，メフロキン（治療と予防）とファンシダール（治療のみ）のみである（経口のキニーネも認可薬であるが，ほとんど用
いられることはない）。その他，ドキシサイクリンも使用可能であるが，わが国ではマラリアに対して適応が認められていない。このような貧弱なマラリア診療体制を補うた

２
１８

図１ わが国における年間マラリア患者数
木村らによる全国集計（１
９
９
０-１
９
９
９，文献８）：-２０
００，文献９）：，感染症法（旧伝染病予防法）に基づく届出数（１９９０，東京大学医科学研究所附属病院の集計（１
９
９
２-２
０
０
０，文献７）： を示す。

めに，創薬等ヒューマンサイエンス財団総合研究事業「熱文献
帯病に対するオーファンドラッグの開発研究」班が抗マラ
１．大友弘士 最近２０年間の輸入マラリアの現状について寄生
リア薬を輸入，保管している。２００
３年１２月の段階で，静注
虫学雑誌４１（Suppl）
：７
９，１
９
９
２
用キニーネ，リン酸プリマキン，硫酸クロロキン，アーテ
２．大友弘士 過去５年間の国内マラリア発生状況について寄
スネート，アトバコン／プログアニル合剤，
アーテメーター
生虫学雑誌４２（Suppl）
：１
３
７，１
９
９
３
／ルメファントリン合剤を準備し，東京大学医科学研究所
３．増田剛太 都立駒込病院で１
９
７
５-１
９
９
２年に診療したマラリ附属病院が中央保管施設としてこれらの薬剤を備蓄し，使アの集計成績 日本熱帯医学会雑誌２
１：３
２，１
９
９
３
用頻度の高い薬剤および緊急性のある薬剤を全国２２の保管
４．Ohnishi K, Murata M. Malaria--eight years of experience in a To施設に配布している。保管薬剤の詳細と保管施設に関して
kyo metropolitan hospital. Intern Med. 35: 111, 1996.
は，研究班ホームページ（http://www.ims.u-tokyo.ac.jp/didai
５．大友弘士，木村幹男，狩野繁之，竹内勤，早野真史，熊谷正広，渡辺直煕感染症新法施行後の輸入マラリア発生状況/orphan/index.html）をご参照いただきたい。
日本熱帯医学会雑誌２
９巻増刊：２０２，２００１
認可薬および研究班保管薬により，マラリア治療に関し
６．増田剛太，味澤篤，根岸昌功，今村顕史，貫井千津子，安ては一応の体制が整っているといえるが，研究班の保管薬部久美子 都立駒込病院のマラリア症例 感染症学会誌
剤の輸入および薬剤の患者への供給体制については解決す
７
５：６
１
６，２
０
０
１
べき問題が残されている。また，研究班保管薬は予防のた
７．三浦聡之，木村幹男，日谷明裕，鯉渕智彦，中村仁美，遠めの供給は行っておらず，わが国で使用できるマラリア予
藤宗臣，高橋孝，小田原隆，中村哲也，岩本愛吉東京大学
防薬はメフロキン１剤という状況である。WHO は，渡航医科学研究所附属病院におけるマラリアの統計 過去１０年する国ごとにメフロキン，クロロキン，プログアニル，ド間の検討感染症学会誌７
６：６
７
７，２
０
０
２
キシサイクリンのいずれかをマラリア予防に推奨している。 ８．Kimura M, Suzaki A, Matsumoto Y, Nakajima K, Wataya Y, Ohtomo H. Epidemiological and clinical aspects of malaria in Japan.
わが国においてこのうちの１剤しか処方できないという現J. Trav. Med. 10: 122, 2003
実は，年間１００
０万人以上のヒトが海外に出かけ，自衛隊の９．病原微生物検出情報２
２：２
３，２
０
０
１
海外派遣が行われている現状を考えると憂慮すべき問題と
１
０．Muentener, P. Schlagenhauf, P. Steffen, R. Imported Malaria:
思われる。行政の対応を期待したいところである。
Trends and perspectives. Bul. WHO. 1999, 77: 560-566

２１９

デング熱の臨床と診断
吉田邦仁子
国立国際医療センター

エイズ治療研究・開発センター＊

はじめに
デング熱（Dengue fever; DF）は再興感染症の一つであり，全世界では年間約１億人がデング熱を発症し，５０万人がデング出血熱（dengue haemorrhagic fever; DHF）を発症すると推定される。熱帯・亜熱帯地域への渡航者増加に伴い，近年我が国でも増加傾向にある輸入感染症であり，その臨床像および各種検査を通じた早期診断が重要な鍵となる。
本稿では，デング熱及びデング出血熱に関し概説するとともに，我々が過去３年間に経験した，デング熱８症例の臨床的検討を行う。

病原体及び感染経路
デングウイルスは，フラビウイルス科に属し，４つの血清型が存在する。同型に対しては終生免疫を獲得するが，他の血清型に対する交叉免疫は数ヶ月で消失し，二次感染時にデング出血熱になる確立が高くなるといわれている。
感染媒体は主にネッタイシマカであり，時にヒトスジシマ
カも媒介する。流行地域は，ネッタイシマカの生息地である，北緯および南緯３５度の範囲に含まれる，熱帯・亜熱帯地域の１
０
０カ国以上にも及ぶ。発症１日前から発症後５日頃の，ウイルス血症期の感染者を吸血した蚊が感染し，８〜１２日の潜伏期の後，吸血を繰り返すことでヒトにウイルスを感染させる。同一蚊による頻回の吸血のため家族や同居者などが次々と数日の間に発症することを認めることがある。

臨床像及び診断
その臨床像から，非特異的症状のデング熱・出血傾向を

Table 1: Grading severity of Dengue haemorrhagic fever.
Grade１

発熱・非特異的症状，
Tourniquet test 陽性・打撲後の皮下出血

Grade２

Grade１に加え，自発的出血の存在

Grade３

頻脈・脈拍微弱・脈圧低下（２０!Hg 以下）
皮膚冷湿感・不穏等の循環障害

Grade４

ショック状態，血圧・脈圧測定不可※Grade３・４がデングショック症候群（Dengue Shock Syndrome, DSS）に相当する。

＊東京都新宿区戸山１‐
２
１
‐１ ０
３
‐
３
２
０
２
‐
７
１
８
１"

伴うデング出血熱・ショック症状を伴い重症化するデングショック症候群の３つに大別される。WHO による，デング出血熱の重篤度による分類を示す（Table１）。
デングウイルスに感染した場合，不顕性感染に終わる割合が高く，症状を示す場合は，多くがデング熱と呼ばれる
一過性熱性疾患を呈する。２〜１
５日の潜伏期間の後，突然の発熱，頭痛特に眼窩痛，筋肉痛，関節痛を呈する。解熱時に一致して，胸部・体幹から始まる斑状丘疹が出現し，四肢・顔面へ広がるが，この発疹は数日で自然消褪する。
これらの症状は１週間程度で消失し，通常後遺症なく回復する。血液所見では白血球減少，相対的リンパ球増加，血小板減少，肝機能障害などを認める。
デング熱とデング出血熱を病態生理学的に区別するもの
は，血管透過性の亢進による血漿漏出である。通常のデング熱とほぼ同様に発症するが，第３〜５病日に血漿漏出と出血傾向を主症状とする重篤な病態を示す。血液検査にお，ヘマトクリッ
いても，血小板数低下（＜１０．
０×１０４／µl）
ト値２
０％以上の上昇，血液凝固時間延長等を認める。血漿漏出が進行すると，循環血液量の不足からデングショック症候群を呈する。出血傾向としては，Tourniquet Test 陽性，
出血班，鼻血，消化管出血等が半分以下の症例で認められ，重篤な例では DIC に陥ることもある。
以上のような渡航歴・臨床所見に加え，確定診断には，
血清 ELISA 法によるデングウイルス特異的 IgM 抗 体・IgG 抗体の検出，HI 抗体価等が用いられ，その他ウイル
ス分離や，PCR 法によるウイルス遺伝子の検出も非常に有用である。初感染・二次感染の鑑別に関しては，HI 抗体価の推移及び IgM・IgG 比に注目する必要がある。
デングウイルスに対する特異的治療はなく，補液・疼痛
コントロールなどの対症療法が中心となる。一般にデング出血熱の患者は症状が回復し始めると後遺症を残さず迅速に回復する。患者の隔離は不要であるが，感受性のある媒介蚊が生息している可能性があれば患者から吸血しないよう蚊の進入を阻止する必要がある。

当院におけるデング熱症例
次に，当院にて過去３年間で経験した，デングウイルス
感染症８症例の臨床的検討を行った。Table１に，渡航歴・臨床及び血液検査所見を，Table２に血清学的診断及びデング出血熱重篤度 Grading を提示した。対象は２
０
０
０年７月
〜２
０
０
３年３月に当科を受診し，デング熱の診断に至った８２
２
０

Table 2: 8 cases diagnosed Dengue between July 2000 and May 2003.
症
例

年
齢

性
別

発症日

１ ２
８ 女 ２
０
０
０．
７．
１
４

感染推定国
ドミニカ

２ ２
９ 男 ２
０
０
１．
１．
１
０ インドネシア

発症
〜受診
の期間
３日
３日

皮疹部位

出血傾向および
血漿漏出症状最小の 基準値より
血小板数 の Ht 上昇 IgM Ab（１０４／ul） 度（％）
４．
８
−
＋

上下肢

−

−

−

５．
７

IgG Ab血清
PCR

DHF Grading

−

施行せず

−

−

−

−

Type２

−
−

３ ２
６ 男 ２
０
０
２．
５．
８

タイ

５日

全身

−

２．
０

３．
０

＋

＋

Type１

４ ３
０ 女 ２
０
０
２．
６．
８

カンボジア

１日

上下肢

Tourniquet test 陽性

６．
８

２
２．
０

−

−

Type４

Grade１

５ ２
５ 女 ２
０
０
２．
６．
１
４ ホンジュラス

２
８日

−

胸水・腹水

２．
０

２
５．
５

−

＋

−

Grade２

６ ２
５ 男 ２
０
０
２．
８．
４

タイ

１
７日

上下肢

眼底出血

６．
８

１
８．
０

＋

−

Type１

Grade２の可能性

７ ２
２ 女 ２
０
０
２．
８．
５

ラオス

７日

下肢

眼底出血・鼻出血 （２
２．
７）
※ （−）
※

＋

＋

施行せず

Grade２の可能性

８ ２
１ 女 ２
０
０
３．
２．
２
５

フィジー

５日

上肢

Tourniquet test 陽性

＋

＋

施行せず

Grade１

５．
１

２
１．
０

症例で，男性３例，女性５例，平均年齢は２５．
７歳であった。 で，早期診断において PCR 法が有用であった。PCR 陰性
主訴は７例が３９℃以上の発熱，１例が視野障害であった。
であった症例５は，前述の如く治療後受診であり，発症後感染推定国は，東南アジアが５例，中米が２例，オセアニ
１
７日目の血清を用いたため，ウイルス分離に至らなかった
アが１例であり，すべて過去にデング出血熱の報告のあると考えられた。
地域に合致していた。夏季・冬季の長期休暇に渡航し，現地の雨季に合致したケースが多く，発症後受診までの期間
おわりに
は１〜２
８日で，平均１１日であった。うち６例が入院加療を
デング熱は約３年周期で流行することが知られているが，必要とした。臨床症状は，平均６−７日間持続した３９℃以
００
１年９月ハワイ・マウイ島，２００２年ブ
上の発熱を全症例に認め，筋肉痛４例，頭痛２例を認めた。 最近の outbreak は２
ラジル南東部・中米（ホンジュラス・エルサルバトル）・皮疹は６例に四肢を中心に認め，出現時期は，発症後平均東南アジア（マレーシア・タイ・ベトナム）
，２
０
０
３年２月
７日目であった。血液検査では，６例に白血球減少を，７例
オーストラリア（ケアンズ）などで認められている。今回に血小板減少を，５例にマトクリット値の上昇を認めた。
当科において経験した８症例は，これら流行地域に合致し症例７は，発熱後３日目に鼻出血を認め，現地ラオスの病ていた。中でも，ネッタイシマカが絶滅したとされるマウ院にて血液検査・点滴加療を受け，その後視野異常が出現
イ島での outbreak は，大量発生したヒトスジシマカによっするも放置，帰国後当科受診，眼底出血を指摘されたケースであった。当科受診時は data 改善を認めているものの， て媒介されたことが確認された。ヒトスジシマカは，本邦
９
４
２年から１
９
４
５年にかけて長経過中に血小板減少を認めていたものと推察された（※）
。 でも東北地域以南に生息し，１崎・大阪で認められた大流行は，本種が媒介したとされて有熱期を過ぎ発症後平均１０日より，全例に軽度から中等度いる。今後，新たな国内二次感染の可能性の示唆され，警の肝機能障害を認め，うち２例に２−３横指の肝腫大を認
鐘を鳴らすものである。
めた。
我々医療従事者は，帰国後不明熱の鑑別疾患として，デデング出血熱としての，出血傾向・血漿漏出傾向に関し
ング熱の重要性を再確認し，その動向に充分注意を払う必ては，Tourniquet Test 陽性２例，眼底出血２例，血管透過要があると考えられる。
性亢進による血漿漏出症状として，胸・腹水の存在を１例に認めた。これら総合して考えると，WHO デング出血熱
病態分類では，２例が Grade１，１例が Grade２に相当し引用文献た。また，受診迄に時間を要した症例６・７では，当院で１）WHO: Dengue haemorrhagic fever: diagnosis, treatment andの検査結果では基準に達しなかったものの，経過中にcontrol. WHO, Geneva, 1997
Grade２に相当していた可能性が示唆された。デングショッ
２）Guzman
M.G., Kouri G. (2002): Dengue: an update, Lancet inク症候群に相当した症例はなかった。いずれの症例も当院
fect Dis., Jan, 2(1), 33-42
においては輸液などの保存的加療にて症状軽快したが，症
３）Scott B.H. (2002): Dengue, Current Opinion in Infectious Dis例５の２
５歳女性は現地ホンジュラスの病院で血小板輸血を
eases, 15, 471-476
１
０単位×２回受け，その後当院に搬送されたという経緯が４）Tomas J., Gerhard D., Michael H. (1997): Prevalence of infecあった。有症状期間は平均１５日間であった。
tion with Dengue virus among international travelers, Arch In確定診断は，ELISA 法によるデングウイルス特異的 IgMtern Med, 157, 10５）奥野良信，木村朝昭，弓指孝博（２００１）：デングウイルス
抗体・IgG 抗体の検出を，さらに可能な症例では PCR 法の輸入感染症例，感染症，３
１，２，６
７
‐
７
２
によるデングウイルス遺伝子の検出も行った（協力：国立感染症研究所ウイルス第１部）。PCR 陽性例は４例であり， ６）倉根一郎（１９９９）：デング熱・デング出血熱，CURRENT
THERAPY，１
７，２，１
３
１
‐
１
３
５
血清型は１型２例，２型１例，４型１例であった。症例２７）WHO: Communicable disease surveillance and Response (CSR),
及び４は共に発症初期であり，IgM 抗体陰性・PCR 陽性２
２１
http://www.who.int/disease-outbreak-news８）WHO: Dengue Net, http://www.who.int/DengueNet
９）CDC: Travelers’ Health, http://www.cdc.gov
１０）鵜飼環栄，伊藤博隆（１９９９）：眼底出血を伴うデング熱の１例，眼科臨床医，９
３，１
２
８
５．

１
１）Haritoglou C, Scholz F (2000): Ocular manifestation in dengue
fever, Ophthalmaloge, 97, 433-436.
１２）Wen K.H, Sheu M.M (1989): The ocular fundus findings in dengue fever. Gaoxicng Yi Xue Ke Xue Za Zhi, 5, 24-30.

Dengue and Dengue haemorrhagic fever.
KUNIKO YOSHIDA
Abstract: Dengue fever is an important health problem for travelers to all endemic countries. Dengue virus which
has four major serotypes is transmitted by the mosquito, Aedes aegypti. New infection with a particular serotype
causes antibody-dependent enhancement. Dengue fever causes negligible mortality, but re-infection to the otherserotype leads to the risk of developing the significantly more dangerous dengue haemorrhagic fever (DHF) anddengue shock syndrome (DSS). We reviewed 8 cases who were consulted to our clinic after returning from tropicaland subtropical countries and diagnosed Dengue between July 2000 and May 2003. 3 cases were male and 5 werefemale whose mean age was 25.7 years old. 5 cases from Southeast Asia, 2 from Central America and1from Oceania. To differentiate dengue cases, clinical evaluation and laboratory diagnosis were used. 7 cases (87%) complained high fever at the first examination. The most common presenting features of Dengue were thrombocytopenia (87%) and leukopenia (75%) in laboratory. Clinically, high fever (87%), rash (72%), myalgia (50%), headache (25%), pain in orbit (13%), visual impairment (13%) were inspected. Those who complained visual impairment were pointed as hemorrhage in the eyeground. The dengue cases were classified as dengue fever (3 cases,
37.5%), DHF (5 cases, 62.5%), and no DSS. With serological confirmation, primary antibody response was observed in 6 cases (75%), Dengue virus isolation were done for 5 cases, 4 (80%) were positive. Dengue serotypes
were 2 cases were typel, 1 was type 2 and 1 was type 4. The prevalence of dengue fever appears to be increasing intravelers, which calls special attention for health care professionals. The clinical presenting features provide important guides to establishing the diagnosis.

AIDS Clinical Center,
International Medical Center of Japan, Japan.

２２３

旅行者下痢症−横浜市立市民病院の症例を中心に−
足立拓也

横浜市立市民病院

はじめに
海外渡航者が健康上の問題から医療機関を受診する際，圧倒的に多い症状は下痢である。ことに発展途上国からの帰国者に多く，いわゆる熱帯地域を１か月間旅行すると，３〜８割の旅行者が一過性にせよ下痢を経験するといわれる!。
本稿では経口による感染経路の共通性から，下痢が症状である旅行者下痢症に，症状としては発熱性疾患である腸チフス・パラチフスを加え，輸入腸管感染症としても述べることとする。

方法

旅行者下痢症と腸チフス・パラチフスの臨床的特徴を検討する目的で，２０
０
１年１月１日から２
０
０
３年６月３
０日までの
２年６か月の期間に当院を受診した計３０７症例を，レトロ
スペクティブに分析した。渡航中あるいは帰国後に下痢をTable 1. Countries and areas where enteric infections
were acquired during international travel:Yokohama Municipal Citizen’s Hospital, between
1 January 2001 and 30 June 2003
Country and area
Asia
Indonesia
ThailandIndia
Vietnam
Cambodia
China
Malaysia
Philippines
Nepal
Korea
Hong Kong
TaiwanOther countries
Subtotal

No. of cases

(%)

６
２
４
９
４
３
１
９
１
９
１
５
８
８
８
５
４
４
１
７
２
６
１

１
９．
６
１
５．
５
１
３．
６
６．
０
６．
０
４．
７
２．
５
２．
５
２．
５
１．
６
１．
３
１．
３
５．
４
８
２．
３

Africa

３
４

１
０．
７

Latin America

１
０

３．
２

Australia/Pacifics

６

１．
９

Other areas

６

１．
９

３
１
７

１
０
０．
０

Total *

＊Total patients 307, including multiple-country visitors 10

感染症部

きたした，いわゆる旅行者下痢症が２９８例，腸チフス・パ
ラチフスが９例である。男性１６
６例，女性１４
１例，受診時の平均年齢は３
２．
５歳であった。

結果および考察
下痢を発症したか，発症する直前に滞在していた国・地域を，推定感染国として Table１に示 す。イ ン ド ネ シ ア
（１
９．
６％）
，タイ（１
５．
５％）
，インド（１
３．
６％）の３か国でTable 2. Causative agents of enteric infections among international travelers:Yokohama Municipal Citizen’s Hospital, between 1 January 2001 and 30 June 2003
Infectious agent
Bacteria
Shigella species*
Diarrhogenic E. coli †Campylobacter jejuni
Campylobacter coli
Nontyphoidal Salmonella‡
Salmonella Typhi
Salmonella Paratyphi A
Plesiomonas parashigelloides
Vibrio parahaemolyticus
Aeromonas hydrophila
Subtotal

No. of strains

(%)

３
０
２
６
２
０
２
１
７
４
５
９
４
２
１
１
９

２
０．
１
１
７．
４
１
３．
４
１．
３
１
１．
４
２．
７
３．
４
６．
０
２．
７
１．
３
７
９．
９

Parasites
Giardia lamblia
Cryptosporidium
Metagonimus yokogawai
Others§

１
４
２
３
１
０

９．
４
１．
３
２．
０
６．
７

Virus
SRSV
Total

１
１
４
９

０．
７
１
０
０．
０

＊S.sonnei 23, S.flexneri 6, Shigella UT 1†ETEC (O6) 9, etc‡Serotypes O76, O84, O94, O3 & 103§Trichuris trichura ova 2,
Taenia saginata 2,
Strongyloides stercoralis 1,
Ancylostoma ova 1,
Heterophyes 1,
Endolimax nana 1,
Iodamoeba buetschlii 1,
Pentatrichomonas hominis 1

133 cases were positive for causative infective agents out of
307 patients, and 149 strains were isolated, including 15 casesof multiple infections

２
２
４

ほぼ半数を占め，アジア地域が全体の８割を占めた。出張や赴任目的の渡航が多いはずの中国，韓国，台湾は相対的には下位であり，仕事目的の海外渡航者と比較して，観光目的の渡航者が旅行者下痢症の多くを占めていることがうかがわれた。こうした渡航者の問診では，観光旅行中の生
水や生の食品の飲食，屋台での喫食，河川での水泳などの行動歴が少なからず聴取され，こうした旅行中の気軽な行動が感染リスクを高めている一因となっていることが推定された。
３０７症例のうち１
３
３例から病原微生物が証明された（陽性率４３％）。病原微生物１４９株の内訳を Table２に示す。多い
ものから，赤痢菌（２０．
１％），下痢原性大腸菌（１７．
４％），
カ ン ピ ロ バ ク タ ー（１４．
７％），非 チ フ ス 性 サ ル モ ネ ラ（１１．
４％）であり，細菌性腸炎が４分の３を占め，チフス性疾患が６．
１％を占めた。細菌以外では，ジアルジア症が全体の９．
４％とかなりの割合を占めた。少数ながら寄生虫疾患も散見された。
２類感染症である細菌性赤痢については，最近では Shigella sonnei や S. flexneri などによる軽症例がほとんどで，S.
dysenteriae 感染により発熱・腹痛・頻回の膿粘血便をきた
し，重症となる例は今回の調査では認めなかった。自覚症状は軽微であるが，検疫所の検便で S. sonnei などが検出されて受診に至る例もしばしば経験した。治療はニューキノ
ロン常用量を５日間経口投与する。
下痢原性大腸菌の中では，突然の水様下痢をきたし，コ
レラと臨床症状が似ている毒素原性大腸菌（Enterotoxigenic
Escherichia coli: ETEC）感染症が比較的多くみられた。経口ニューキノロンが有効であるが，自然経過でも治癒し，予後は良好である。腸管出血性大腸菌（Enterohemorrhagic
E. coli: EHEC）感染症は腸管出血や腎障害をはじめ，急速に全身状態が悪化するため，最も注意が必要なものである。
しかしながら，今回の２年半の観察期間ではみられなかった。
次いで，カンピロバクター，サルモネラと，国内でもしばしば経験する腸炎起炎菌が続くが，これらの臨床的特徴
は国内発生例と同様と考えてよい。いずれも一時的な禁食と輸液などの対症療法のみでも自然治癒する，予後良好な疾患であるが，カンピロバクターでは最近のキノロン耐性株の増加が問題となっている。
２類感染症である腸チフス・パラチフスは，汚染された水や食物を経口摂取することで感染が成立する点は，他の感染性腸炎と同様であるが，腸管内のマクロファージに貪食されたのち血流に入り，細胞内で増殖する，本態は菌血症と考えてよい発熱性疾患である。第一選択薬は細胞内移行性の優れているニューキノロンで，常用量の３分の４を２週間経口投与する。いわゆるオールドキノロンであるナリジクス酸（Nalidixic acid: NA）に耐性を有するものはニューキノロンの最低発育阻止濃度（Minimal inhibitory

concentration: MIC）も上昇しているため，ニューキノロン
低感受性株と呼ばれ，ニューキノロンによる治療が奏効しにくくかつ再発しやすい。インド亜大陸や東南アジアでこうした低感受性株が急速に増加していることは深刻な問題である。同地域から帰国した腸チフス・パラチフス患者はNA 耐性の有無を調べ，NA 耐性であればニューキノロンと第三世代セフェムを併用することで，より高い治療効果が期待できる!。
コレラは旅行者下痢症のなかでも大量の下痢により急速な脱水をきたす，臨床上きわめて重要なものであるが，その頻度は低く，今回の症例のなかには認めなかった。最近
は古典的なアジア型より病原性の低いエルトール型が多い。
原虫のなかで最多のジアルジア症も，臨床症状から細菌性腸炎と区別するのは困難である。便鏡検で栄養型または嚢子を証明することで診断する。治療はメトロニダゾール
経口が有効であるが，難治性のものや再発する場合は，再治療やチニダゾールへの薬剤変更が必要になることもある。
男性同性愛者の性行為感染症の一面もあるため，難治例では注意深い問診と，パートナーの検便，陽性例では両者の治療が必要である。
一般には，旅行者下痢症をきたす疾患は重症化するものは少なく，当院の症例も治療により，または自然経過で全例が治癒した。重篤な合併症はみられなかった。
汚染された水や食物を介しての経口感染であるので，生水・生の食品・屋台で売られている食品を避けることと，石鹸での食前手洗い励行が予防として勧められる"。
旅行者下痢症の治療は，経口補液も含めて第一に輸液であり，ほとんどの場合はこれのみで十分である。発熱または血便を伴う場合は，便検体を採取後に経口ニューキノロ
ンを３日間投与する。妊婦や小児の場合はニューキノロンが原則禁忌であるため，輸液を中心とした対症療法を行い，検便の結果に基づいて特異的抗菌治療の必要性を検討する。
原虫・寄生虫疾患の可能性もあるため，細菌培養だけでなく便鏡検もあわせて行う。
従来ニューキノロン感受性であった起炎菌のうちいくつかの属種で耐性株が増加しているため，起炎菌同定・薬剤感受性をふまえた，特異的な治療薬の選択が望ましい。

文

献１）足立拓也，増田剛太，今村顕史，味澤篤，根岸昌功，
高山直秀，滝永和美，高野さかえ（２０００）：ニューキ
ノロン低感受性菌を分離した腸チフスの２症例。感染症学雑誌，７５，４
８−５２２）International travel and health: vaccination requirements andhealth advice: situation as on 1 January 2001, World HealthOrganization, Geneva
３）Ryan, E.T. and Kain, K.C. (2000): Health advice and immunizations for travelers. New Engl. J. Med., 342, 1716-1725

２２５Traveler’s diarrhea
TAKUYA ADACHI
Abstract: Diarrhea is by far the most common health problem encountered with travel to developing countries.
298 cases of traveler’s diarrhea and 9 cases of typhoid and paratyphoid fever were summarized as intestinal infection. All patients were affected with either diarrhea or enteric fever during or shortly after their trip overseas andvisited the Department of Infectious Diseases at Yokohama Municipal Citizen’s Hospital from January 2001 toJune 2003.
The most common countries of disease acquisition were Indonesia (20%), Thailand (16%), and India (14%). 82%
of all cases were acquired in Asian countries.
From 133 among 307 patients (43%), 149 strains of causative agents were identified. The leading causes were
Shigella (20%), diarrhogenic Escherichia coli (17%), Campylobacter (15%), nontyphoidal Salmonella (11%), andSalmonella Typhi and Paratyphi A (6%). 80% of causative agents were bacteria. Protozoa and parasites were lesslikely causes, accounting for 19% of infection, including 9% of giardiasis.
The most important factor in treating diarrhea is the replacement of lost fluids. Antibiotics are usually not requiredwith acute watery diarrhea, which are usually self-limited with supportive treatment. If blood occurs in the stool, or
if there is fever, empiric antibiotic therapy should be considered. A short course of fluoroquinolone can be considered in such cases.
There have been increasing cases of enteric fever with decreased susceptibility to fluoroquinolones. Resistance tonalidixic acid on disk diffusion susceptibility testing and clinical fluoroquinolone treatment failure are the key findings of decreased susceptibility strains. Intravenous administration of a third generation cephalosporin in addition
to fluoroquinolones is useful to treat such resistant strains.
There is a tendency that the longer the traveler stays abroad the greater the risk is to acquire enteric fever or intestinal parasite infection.
Attention to food and beverage preparation can decrease the likelihood of developing traveler’s diarrhea. Bacteriological stool test is incredible for appropriate diagnosis and treatment.

Department of Infectious Diseases, Yokohama Municipal Citizen’s Hospital

２２７

輸入感染症患者に対する臨床現場での初期対応
岩!惠美子
仙台検疫所

１．はじめにアジアの一地域で始まった SARS（重症呼吸器症候群）の流行は，現代社会の中での感染症の脅威，すなわち，感染症が短時間で地球規模の流行に発展する可能性があることを私達に実感させてくれた。実際，海外では，動物との接点から発生する重篤で感染力の強い感染症が多く，交通機関の発達した現代では，これらが国際交流によって頻繁になった人の移動とともに，容易に国境を越えるようになってきたのである。このような状況の中で，感染症から国民の健康を守るためには，感染者を早期に発見し，良質で，適切な医療を提供することで患者を救うことと同時に，そこからの二次感染を防ぐことが必要になってくる。すな
わち，医療機関での感染患者への初期対応が，患者の早期発見や適切な医療の内容につながることから，その役割は非常に大切になってくる。従って，現在の日本の医療関係者には，海外の感染症の流行情報や，その診断，治療などに必要な知識が求められることとなる。

る。特にアジア地域は腸管系感染症の多発地帯の一つであり，渡航先での食事などが原因で，罹患して帰国する人は後を絶たない。また，この地域の環境衛生などは，決して良好ではなく，蚊やダニ，ネズミなどの媒介動物や，病原体を体内で増やしている増幅動物（リザーバー）が普通に生息しており，多くの感染症の流行を起こしている。その代表として，マラリア，デング熱，レプトスピラ症などが挙げられ，これらは動物が関係していることから，季節によって流行に差がみられる。
このようなアジアの環境の中では，これらの感染症に罹患して帰国する人もみられるのは当然であろう。
また，近年では，このような古典的な感染症のみならず，
国際的に感染拡大する可能性の高い，強い感染力を持つ感染症の発生もみられている。まさに，今回流行した SARS
はその典型であろう。アジアでは人と動物の接点が近いた
めに，動物由来の強い感染力を持つ重篤な感染症に人が罹患する機会は多く，その上，アジアの高い人口密度や頻繁な人の移動などによって，世界的な流行を引き起こす可能性は高くなっている。

２．日本の海外渡航者と渡航先での感染症事情
交通機関の発達は，人や物の国際交流を盛んにした。日本では，年間１，６０
０万人の日本人が海外に渡航し，さらに年間５００万人の外国籍の人が来日している。日本人旅行者の特徴は，その年齢分布でも顕著なように２０歳代の女性が最も多く，ほとんどが一週間以内の短期旅行であり，その旅行先として三分の一がアジアを選んでいることである。
図１：地域別渡航者数の推移

また，日本に来日する人の多くもアジアの人々であり，日本はアジアと密接な関係にある。
このように，多くの人々が往来しているアジアは，また，多くの感染症が日常的に発生し，注意を要する地域でもあ３．輸入感染症対策の中での検疫所の役割
日本では海外から入ってくる感染症を監視しているのが検疫所である。交通機関の発達とともに，国境を越えての人の往来はほとんどが航空機によるものとなり，人の動き
はますます高速かつ広範囲になってきた。その結果，人とともに動く感染症の動きも，より複雑でスピーディーになってきた。
また，従来，国内で注意すべき輸入感染症と考えられてきた感染症は，腸管系感染症ではコレラ，細菌性赤痢，腸チフスなど，そして近年，日本の多くの若者が免疫を持たないことで感染する A 型肝炎，さらに，蚊によって媒介されるデング熱，マラリアなどであり，検疫所でもこれらの感染症に関しては水際での検査体制の充実を図り，患者の発見に力を注いできた。しかし，地球上での感染症の動向を考えると，これらだけでは済まなくなってきており，
ますます水際である検疫所の感染症の監視は難しくなってきている。
その原因の一つには，特に感染力の強い重篤な感染症では，その潜伏期が長いことがあげられる。日本人の海外旅
行の形態をみると，多くが短期旅行であることなど，感染症の症状が現れないうちに空港検疫所を通過し入国するため，空港検疫所での患者の発見が難しくなっている。また，検疫のための手続きや検査などの煩わしさから，入国者に

２２８対する検疫の際に虚偽の申告をする場合が多く，これらも入国時の監視を困難とする原因の一つとなっている。
これらの背景を考慮し，検疫所では水際での対応だけでなく，海外から入ってくる感染症に対応する医療機関の支援，入国者の健康管理や感染拡大防止を図るための施策も展開している。
!感染予防
感染症対策の基本は予防にある。特に海外で流行する感染症は，国内で患者発生のみられる感染症とは異なるものが多いために，それに対する知識を日本の医療関係者は十分に有していない。それらを考慮し，検疫所では，医療関係者が診察する際の助けとなるよう，医療関係者に対しても海外で流行している感染症の流行情報を HP などを通じて提供している。
また，市民に対しては，予防接種の実施により，海外の旅行先での感染を防ぐことの可能であることなど，感染症の予防啓発を HP やパンフレットなどを通じて行っている。
予防接種に関しては，検疫所で「トラベルメイト」という予防接種記録の手帳を配布し，その手帳の利用を旅行者に呼びかけている。しかし，現在までに，この手帳の普及は十分ではない。

また，予防接種によって防ぐことの出来る感染症から国民を守るために，海外へ渡航する前に予防接種を勧めると同時に，検疫所でも海外旅行のための予防接種を実施している。いくつかの検疫所では海外旅行外来を地域の医療施
設と共同で開設し，そこで予防接種を実施するとともに予防教育の場としても活用している。
実際，検疫所は交通の不便な空港ないしは港などにあることが多いため，そこでの予防接種は利用されにくい。その点からも，市中の医療機関などでの海外旅行外来の開設
は，国民にとって極めて有効である。
"海外旅行外来
先進国では，海外へ旅行する人，特に途上国への旅行を目指す人の多くは，海外旅行外来を訪れ，そこで渡航先に応じた予防接種やその相談，感染予防の知識，予防薬などの処方を受けている。また不幸にも感染して帰国してきた
場合にも，この海外旅行外来を相談，診察，治療のために利用している。
しかし，日本ではこのような外来を開設している施設は極めて少なく，それが海外旅行前の予防接種の普及を阻んでいる。
そこで，海外旅行外来の重要性から，検疫所でも外来開

図２：海外旅行外来での予防接種※その他：破傷風，A 型肝炎，B 型肝炎，狂犬病，ポリオ

２２９設を考え，いくつかの検疫所でスタートし始めたところである。
仙台検疫所では海外旅行外来を国立仙台病院，国立療養所盛岡病院で開設し，予防接種，相談業務を行っている。
その外来の開設は，実際に寄せられるメールや FAX など
での相談や電話相談も増やしており，特に SARS のような国際的に感染拡大し，多くの人々にとって関心のある感染症が流行しているときには，相談窓口として大いに役立っていることが統計からも判る。
実際，感染患者の早期発見が感染拡大にとっては非常に意味があり，旅行者からの相談によって，症状が重症化す
る前に適切な医療機関に誘導することや，医療関係者への適切な情報の提供がそれに役立つことはいうまでもない。
このような医療機関と市民の対応窓口としても，海外旅行外来の役割は大きいと考える。
"入国後の健康異変に対する対応
感染症に罹患した患者をできるだけ迅速に医療機関へ誘導し，適切な医療を提供することが感染拡大を防止するためには必要不可欠である。特に海外からの感染症の多くは重篤で感染力が強いことを考えると，発症してから医療を受けるまでの時間の短縮が通常の感染症以上に大切になる。
検疫所では従来から，電話などでの相談を通じ，医療機関への誘導を行ってきたが，一般への知名度は低く，利用は少ないのが現状である。しかし，現在のような感染症の動向を考えると，より早い対応や有効な感染症対策が必要であり，そのためには検疫所による積極的な関与が求められてきている。今回，１１月に行われた法律の一部見直しで，
SARS に関しては流行地域から入国した人の１０日以内に発生した健康異変を検疫所に届け出ることが義務付けられ，
少しでも患者発見までの時間の短縮を図り，感染拡大や流行阻止の一端を担うために積極的に検疫所が関わるような体制に整備された。

医療関係者による感染症対策の不備が深刻な問題を生んできた。今回の SARS でも同様に多くの国で医療従事者の感染が流行を大きくしており，感染症患者の治療に際しては，診断，治療に関する充分な知識も必要であるが，それと同時に，日頃からの医療関係者の標準予防策の徹底が求められ，病院での感染対策の充実が必要になっている。

５．おわりにSARS の流行が私たち医療関係者に残してくれたものは，感染症の怖さだけでなく，もっと大切なものを数多く残してくれたと思われる。
特に，感染症に関する情報，治療法などの知識もさることながら，このような感染症に罹患した患者に日常の診療で遭遇する可能性が高いことを教え，そして，それらに自らが感染しないように，また，自らが原因となって感染を拡大させないように努力しなさいと諭してくれたような気
がする。

参考文献

１）法務省：日本人の出国状況・外国人の入国状況，法務省
ホームページ
２）Center for Disease Control and Prevention (2001): Health Information for the International Travel 2001-2002: US Department
of Health and Human Services, Public Health Service, Atlanta３）World Health Organization (2002): International Travel and
Health, Geneva４）World Health Organization (2003): Consensus document on theepidemiology of SARS, Geneva
５）国立感染症研究所感染症情報センター
（２
０
０
２）
：コレラ２
０
０
２
年８月現在，病原微生物検出情報月報（IASR）
，２
３，２
１
９
‐
２
２
０
６）国立感染症研究所感染症情報センター
（２
０
０
３）
：細菌性赤痢
２
０
０
１〜２
０
０
２，病原微生物検出情報月報（IASR），２４，１‐２７）国立感染症研究所感染症情報センター
（２
０
０
１）
：腸チフス・
パラチフス１９９７〜２０００，病原微生物検出情報月報（IASR），
４．輸入感染症などに対する医療機関の対応
２
２，５
５
‐
５
６
輸入感染症の特殊性を考えると，感染症の原因となる病
８）国立感染症研究所感染症情報センター（２００２）：A 型肝炎・
E 型肝炎２００
２年９月現在，病原微生物検出情報月報（IASR），
原体を知ることが非常に大切であり，その上で適切な医療
２
３，２
７
１
‐
２
７
２
が行われることが必要となる。実際，日本の医療機関では，
９）国立感染症研究所感染症情報センター
（２
０
０
０）
：輸入感染症
腸管系感染症に関しても，一般外来でその病原体の検査もとしてのデング熱，病原微生物検出情報月報（IASR），２
１，
実施せずに，いきなり抗生物質投与が始められる場合が多
１
１
２
‐
１
１
３
いことがアンケート調査でも明らかとなった。
１０）国立感染症研究所感染症情報センター
（２
０
０
１）
：輸入マラリ
東北地域の臨床内科医会のメンバーにアンケート調査を
ア２
０
０
０年１
２月現在，病原微生物検出情報月報（IASR），２
２，
実施したが，６
７
５名から回答が得られ（回答率は５
０％）
，そ
２
３
‐
２
４
の中で下痢症の患者に治療を始める前に検便などの病原体
１１）国立感染症研究所感染症情報センター
（２
０
０
４）
：感染症法改正，病原微生物検出情報月報（IASR），２
５，１‐６の検査をする医師が７％にも満たないことが判明した。こ１２）岩!恵美子（２００２）：諸外国における食品媒介感染症に対の結果が全てとは思わないが，日本の医療関係者の感染症する調査の研究（食品媒介感染症における病原体サーベイ
に対する知識や治療法などに大いに問題があることを示唆
ランスシステム構築に対する提言），平成１３年度厚生科学していると思われる。
研究「輸入食品媒介感染症に対する研究」報告書

従来，エボラ出血熱などの重篤な感染症の流行現場では，