ISSN 0915-5813

IASR

Vol. 37 No. 12 (No. 442) December 2016
Infectious Agents Surveillance Report
http://www.nih.go.jp/niid/en/iasr-e.html

Epidemiology of domestically acquired amebiasis as a sexuallytransmitted infection in Japan, 2000-2013 ....................................... 241
Correlation between annual notifications of amebiasis and that ofHIV infection among homosexuals.................................................... 242
A case of amebic colitis diagnosed by colonoscopy .............................. 243
Amebic appendicitis .............................................................................. 245
Endoscopic diagnosis of intestinal amebiasis ...................................... 246
Serum antibody test for anti-Entamoeba histolytica: Potential use
for screening persistently infected asymptomatic cases .................. 248
Amebiasis as a zoonotic disease ........................................................... 249
Influenza virus isolated from the end of 2015/16 season to the early
2016/17 influenza season–Niigata Prefecture .................................. 251

National Institute of Infectious Diseases andTuberculosis and Infectious Diseases
Control Division,
Ministry of Health, Labour and Welfare

Notice from the Ministry of Health, Labour and Welfare: Notice onreporting of Escherichia albertii-Director, Tuberculosis andinfectious disease division, MHLW ................................................... 252
Escherichia albertii food poisoning due to consumption of Nigana
shiraae seasoned mixed salad of nigana (Ixeris dentata) andtofu, May 2016-Okinawa Prefecture ................................................ 252
Foodborne outbreaks attributed to Escherichia albertii and theinvestigation leading to its identification, July 2016-Shizuoka
Prefecture ........................................................................................... 254
Stx2f-positive Escherichia albertii isolated from a patient withhemolytic uremic syndrome, August 2016 ........................................ 255
Infective endocarditis with annular abscess due to multidrugresistant Corynebacterium striatum infection-a surgical case report.. 256<THE TOPIC OF THIS MONTH>
Amebiasis in Japan, week 1 of 2007-week 43 of 2016
Amebiasis is caused by the protozoan parasite Entamoeba histolytica, transmitted through the fecal-oral route. The parasite
is released in the feces as cysts, which may contaminate drinking water or foods. Once the cysts are ingested and reach the small
intestine, they undergo excystation and become trophozoites. Trophozoites migrate to the colon and cause mucosal ulcers in 5-10%of infected persons, resulting in “intestinal amebiasis”. This condition is associated with dysenteric signs or symptoms, such as
mucous and bloody stool, diarrhea, tenesmus (feeling of incomplete defecation) and abdominal pain. Occasionally, the trophozoites
migrate hematogenously further to the liver, lung, brain or skin and produce local abscesses resulting in “extraintestinal amebiasis”,
which is clinically more serious. The World Health Organization estimates that globally several tens of thousands of people die ofamebiasis annually.
E. histolytica infects experimental cynomolgus monkey as well as humans. E. dispar infects monkeys as well as humans but isnonpathogenic and does not require treatment. While E. nuttalli has been detected from Japanese monkeys, its pathogenicity tohumans is unknown (see p. 249 of this issue).
Reports under the National Epidemiological Surveillance of Infectious Diseases (NESID) system
Amebiasis is a category V notifiable infectious disease under the Infectious Diseases Control Law. A physicians who has madea diagnosis of amebiasis (excluding asymptomatic cases) shall notify the case within 7 days (see http://www.nih.go.jp/niid/images/iasr/37/442/de4421.pdf for the notification criteria).
Reports of amebiasis have been increasing in Japan in recent years (IASR 28: 103-104, 2007), and much of this increase has
been due to increase in cases infected domestically (Fig. 1). Among 9,301 cases reported from week 1 of 2007 to week 43 of 2016 (asof 23 November 2016), 7,753 cases (83%) were infected in Japan. There were 1,302 cases infected abroad (including 228 cases thathad visited two or more countries and 102 cases whose country of travel was unknown), such as in China (179 cases), Thailand (149cases), Indonesia (139 cases), Philippines (82 cases), India (59 cases), Republic of Korea (53 cases), Vietnam (47 cases), Taiwan (42cases), and Cambodia (37 cases).
Age and sex distribution: As reported previously, the majority of reported cases were male (IASR 28: 103-104, 2007); amongnotified cases, 8,181 were male (88%) and 1,120 were female (12%). The median age of cases was 50 years (interquartile range:41-59 years) for males and 40 years (interquartile range: 31-48 years) for females (Fig.2). Among females, 115 cases were reported
in 2007 and 121 cases were reported in 2015. Among males, however, 686 and 988 cases were reported for the respective years (a1.4-fold increase), indicating that much of the recent increase was in men (see p. 241 of this issue).
Among 9,301 cases notified during the period, 38 were reported as fatal cases at the time of notification; 37 were male (1 casein his 30s, 5 cases in their 40s, 9 cases in their 50s, 9 cases in their 60s, 8 cases in their 70s and 5 cases in their 80s) and one female
in her 70s.
Figure 2. Age distribution of amebiasis cases by gender,from week 1 of 2007 to week 43 of 2016, Japan

Figure 1. Number of reported amebiasis cases by year,
from 2007 to 2016*, Japan
Domestic cases

1,300
1,200

Imported cases

1,100

1,000
900
800

Unknown

No. of cases

No. of cases

700
600
500
400

MaleFemale

1,000
900
800
700
600
500
400

300

300

200

200

100

100002007 2008 2009 2010 2011 2012 2013 2014 2015 2016 *(1-43w)
Year of diagnosis0510 15 20 25 30 35 40 45 50 55 60 65 70 75 804914 19 24 29 34 39 44 49 54 59 64 69 74 79

Age group (years)(National Epidemiological Surveillance of Infectious Diseases:
as of November 23, 2016)(National Epidemiological Surveillance of Infectious Diseases:
as of November 23, 2016)

1′（239′）（Continued on page 240′）IASR Vol. 37 No. 12（Dec. 2016） 2′（240′）（THE TOPIC OF THIS MONTH-Continued）
Table. No. of reported amebiasis cases, by prefecture, week 1 of 2007-week 43 of 2016
PrefectureNo.cases

HokkaidoAomoriIwate
MiyagiAkitaYamagata
Fukushima
IbarakiTochigi
Gunma
Saitama
Chiba
Tokyo
Kanagawa
NiigataToyamaIshikawa
Fukui
Yamanashi
NaganoGifu
Shizuoka
Aichi
Mie

252
4670
203
3151
136
125
80
96
361
494
1,862
869
120
50
59
38
38
150
121
213
581
88

Per 1,000,000
person-year
4.66
3.41
5.35
8.79
2.90
4.44
6.82
4.28
4.05
4.86
5.10
8.08
14.39
9.77
5.14
4.65
5.13
4.79
4.48
7.09
5.92
5.76
7.98
4.83

Prefecture

No.cases

Shiga
Kyoto
OsakaHyogo
Nara
Wakayama
Tottori
Shimane
Okayama
Hiroshima
Yamaguchi
Tokushima
KagawaEhimeKochi
Fukuoka
Saga
Nagasaki
Kumamoto
Oita
MiyazakiKagoshima
Okinawa
Total

88222985
391
108
48
3122135
154
64
3463
59
22351
3557
8852
63
49
469,301

Per 1,000,000
person-year
6.35
8.57
11.30
7.12
7.84
4.87
5.36
3.12
7.06
5.48
4.49
4.40
6.44
4.19
2.93
7.04
4.19
4.06
4.93
4.42
5.65
2.92
3.36
7.39

*2010 Population Census of Japan(National Epidemiological Surveillance of Infectious Diseases: as of November 23, 2016)

Clinical types: Among notified cases, 7,763 were intestinal amebiasis, 1,131 were extraintestinal amebiasis and 407 wereboth intestinal and extraintestinal amebiasis cases. While it was reported previously that the extraintestinal type was more
frequently reported among males than among females (20% vs. 12%, respectively) (IASR 28: 103-104, 2007), in the present data
(week 1 of 2007-week 43 of 2016), the frequency was comparable, i.e., 12.2% (998/8,181) in males and 11.9% (133/1,120) in females.
In recent years, as intestinal amebiasis cases with specific clinical manifestation of colonic mucosa lesions (but otherwise
asymptomatic) have been increasing reported in males, the increased detections from colonoscopy may be contributing to the risein notifications (see pp. 241 & 246 of this issue).
Geographical distribution: As in 2003-2006 (IASR 28: 103-104, 2007), during week 1 of 2007-week 43 of 2016, prefectures withmajor urban areas, such as Tokyo, Osaka and Kanagawa, reported both the largest number of cases and largest notification rate per
million population (Table).
Infection route: Among the 9,301 cases, the presumed infection route was unknown for 49% of all cases (4,521 cases: 3,984
males and 537 females). Infections attributed to oral consumption (e.g. uncooked foods, fresh fruits or water) occupied 22% of thetotal cases (2,080 cases: 1,778 males and 302 females), though the specific source was not identified in more than 80% of the cases.
Sexual transmission occupied 29% of all cases (2,700 cases: 2,419 males and 281 females); among males, infection throughheterosexual contacts accounted for 1,090 cases and homosexual contacts for 864 cases, while among females, heterosexual infection
accounted for 221 cases and homosexual contacts for 6 cases (for both genders, bisexuals were included in the homosexual contactcategory). Though amebiasis among men who have sex with men (MSM) have been well known (see p. 242 of this issue) (IASR 28:103-104, 2007), amebiasis attributed to heterosexual contact is being increasingly reported (see p. 241 of this issue) (IASR 35: 223224, 2014). Infection of amebiasis among female commercial sex workers (CSW) were reported previously (IASR 24: 81, 2003 & 28:109-110, 2007), and, among the 1,120 female amebiasis cases, 23 were self-reported CSWs.
Laboratory diagnosis: Definitive diagnosis requires laboratory diagnosis to detect the presence of E. histolytica (Laboratory
Manual for the Pathogen Detection: http://www.nih.go.jp/niid/images/lab-manual/entamoeva.pdf in Japanese). Among the 9,301
cases notified, 7,549 were diagnosed by detection of ameba by microscopy, 2,500 by antibody detection, 82 by antigen detection byELISA and 108 by PCR (includes detection by more than one method).
Treatment
Oral administration of metronidazole, which became covered by national health insurance specifically for the treatment ofamebiasis since August 2012, is highly effective and the mainstay of treatment of amebiasis (see pp. 243 & 245 of this issue).
Paromomycin, which is considered to be effective against cyst carriers, has also been covered by national health insurance sinceDecember 2012.
Future challenges
In recent years, reports of non-fulminant amebiasis cases have been increasing (see pp.241 & 248 of this issue). While
asymptomatic cases do not require notification, as asymptomatic carriers are potential sources of infection, and some will go on to
become fulminant, treatment of such carriers is important. Among domestically infected amebiasis cases, while attention has been
paid for amebiasis among MSM, reports of CSW cases (see p. 243 of this issue) continue. The recent increase in notifications ofamebiasis caused by heterosexual contacts may be associated with diversification of sexual behaviors in recent years, which may
result in the ingestion of cysts. Measures against amebiasis should be considered within a comprehensive framework of control
measures against sexually transmitted infections.
The statistics in this report are based on 1) the data concerning patients and laboratory findings obtained by the National Epidemiological
Surveillance of Infectious Diseases undertaken in compliance with the Law Concerning the Prevention of Infectious Diseases and Medical Care forPatients of Infections, and 2) other data covering various aspects of infectious diseases. The prefectural and municipal health centers and publichealth institutes (PHIs), the Department of Food Safety, the Ministry of Health, Labour and Welfare, and quarantine stations, have provided theabove data.

Infectious Disease Surveillance Center, National Institute of Infectious Diseases
Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640, JAPAN Tel (+81-3)5285-1111