豚および野生イノシシにおけるSarcocystis感染

誌名誌名 動物の原虫病 = Journal of animal protozoosis

ISSNISSN 09157506

著者著者斉藤, 守弘萩原, 晶代

巻/号巻/号 28巻1号

掲載ページ掲載ページ p. 25-30

発行年月発行年月 2013年12月

農林水産省 農林水産技術会議事務局筑波産学連携支援センターTsukuba Business-Academia Cooperation Support Center, Agriculture, Forestry and Fisheries Research CouncilSecretariat

Journal of Animal Protozooses Vol. 28, No. 1 (2013）〔原著〕 25

Sαrcocystis miescheriαnαinfection in pigs and wild boars in Japan

Morihiro SAITO and Akiyo HAGIW ARA

Meat Inspection Center of Saii抱机αPrefec；切符

(Received 9 Jul., 2012)

Abstract Of 50 fattened and 50 older culled breeding pigs slaughtered in Saitama Prefecture,

Japan from November 2010 to March 2011, three (6%) culled pigs were positive for Sarcocystis

miescheriana, whereas none of the fattened pigs were positive. Three of 48 (6.3%) wild boars (Sus

sucroj包：） captured in Saitama Prefecture from November 2010 to March 2011 were positive for S.

miescheriana. The S. miescheriana cysts had the thick and radially striated wall. Scanning electron

microscopy revealed many villar protrusions 4-5 μm in len民hon也ecyst surface. A dog fed S.

miescheriana infected meat excreted sporocysts in the feces after day 9.

Key words : dogs, pigs, Sarcocystis, wild boars

Journal of Animal Protozooses Vol. 28, No. 1: 25-3α2013

Introduction

Sarcocystis infections have been reported in domestic

pigs and wild boars in various p紅白 ofthe world: Nor-

way, Netherlands, Germany, Hungary, Bulgaria, USSR,

Fiji, Australia, New Zealand, USA, and Brazil12l. In

Japan, there is little information on Sarcocystis infection

of pig and wild boars.9J_

Three species of Sarcocystis have been recorded

from domestic pigs and wild boars : S. miescheriana, S.

suihominis and S.ρore俳lisand their final hosts are

dogs, humans, and cats, respectively2・5l_ In the present

report the frequency of Sarcocystis infections was sur-

veyed in pig and wild boars in Saitama prefecture,

Japan.

Materials and Methods

Pigs : Fifty grams of car世acmuscle and diaphragm

were individually obtained from 50 fattened and 50

older culled breeding pigs slaughtered in Saitama

Prefecture from November 2010 to March 2011.

Wild boars : Fifty grams of cardiac muscle and

diaphragm were individually obtained from 50 wild

・5-18-24Kamiochiai, Chuoku, Saitama, Saitama 338-0001, Japan

boars captured in Saitama Prefecture from November

2010 to March 2011.

Muscle blocks were dissected into approximately 1

×2×0.5 cm in size and examined for cysts in a plane

perpendicular to the long axis of the muscle fibers.

Thereafter the cysts were directly removed from the

blocks under a microscope7l.

Twentyfive fresh cysts from the diaphragm muscles

were measured with a micrometer and examined也e

s甘uctureof the cyst wall. A part of fresh cysts were

fixed wi也 10%formalin and post-fixed with 1 % osmic

acid. Then they were dehydrated in a series of

ethanol and dried at the critical point After platinum

was deposited, the cyst samples were observed with

scanning electron microscope (Nihon Denshi, JSM司35C)

for the superficial structures such as villar protrusions.

For histopathological examination, tissue samples

were removed from infected muscles and fixed with

10% formalin. The specimens were embedded in

paraffin and sectioned. The sections were stained wi也

hematoxylin and eosin and observed under a light

microscope. Another part of the fixed material was

post-fixed with 1 % osmic acid and embedded in epoxy

resin. The resultant ultrathin sections were stained

wi也 ur叩 ylacetate and lead ci甘ate，叩d由enobserved

26 動物の原虫病 第28巻第l号 （2013)

for the ultrastruture of the cyst wall with a transmis-

sion electron microscope (lOOCX. Nihon Denshi, Japan).

400 g of infected cardiac muscles. All the ingested

dogs were daily examined for sporocysts passed in the

total amount of feces by the flotation method with Two male mongrel dogs, 5-months old, were fed

Fig. 1. Fresh cyst of Sarcocystis miescheriana from diaphragm muscle of a pig (left) and

that of a wild boar (right）.×100

Fig. 2. Cross section of a thick-walled cyst of S. misecheriana in diaphragm muscle of a pig (left) and

that of a wild boar. HE stain ×100

Sarcocystis miescheriana infection in pigs and wild boars in Japan 27

satulated NaCl solution. Fifty sporocysts excreted in

the feces of the animals were observed and measured

with a micrometer under a light microscope.

Result

Three of 50 (6%) culled pigs were positive for

sarcocysts, whereas none of the fattened pigs were

positive. Three of 48 (6.3%) wild boars (Sus sucrofa)

were positive for sarcocysts.

Fresh cysts were 1,080-2,700×78-90 μm in size. All

S訂 cocystshad the radially striated wall, whose thick-

ness ranged from 4 to 5 μm (Fig. 1). These structural

Fig. 3. Transmission electron micrograph of S. miescheri (upper left) and出atof a wild boar (upper right）.×10,000 Scanning electron micrograph

of S. miescheriana cyst in diaphragm muscle of a pig : Note palisade-like villar protrusions on cyst wall (lower left) and也atof a wild boar (lower right）×2,000

28 動物の原虫病 第28巻第1号 （2013)

4際

‘・。． ．

，

． ，

，

Fig. 4. A sporocyst of S. miesche1叩naexcreted in feces of dog, which were fed a Sarcocystis

infected raw pork. ×400

feature were also confirmed on histopathological exam-

ination (Fig. 2). Transmission and scanning electron

microscopy showed palisaid-like villar protrusions 4-5

×0.7-lμm in size, on the cyst wall (Fig. 3).

The dogs fed infected meat passed sporocysts in the

9 days after ingestion. Sporocysts were ellipsoidal and

measured 12-13×9.5-10 μm in size (Fig. 4).

Discussion

The incidence rat of Sarcocystis infection is known

to increase with the age of host animals. Boch et al.1)

d巴tectedS. miescheriana cysts in 25.5% of older pigs

and in 9.7% of fattened ones in southern Germany.

Seneviratana et al.10) reported that 12.7% of 55 older

than one year were positive but none of 48 pigs less

than one year old were positive for Sarcocystis sp.,

which was not identified the species but seem to be S.

miescheriana because the sporocysts were recoverd

from dogs fed the infection meat. On the other hand,

it is reported that the infected rate of S. miescheriana

in the pig and the wild boar were both 7% in the latter

half of the 20th century in Japans.9l. Since then, there

is no report until the present study出atrevealed the

infection rate equivalent to past data.

Three species of Sarcocystis have been reported in

pigs : S. miescheriana, S. suihominis, and丘ρore俳Lis,

which utilize dogs, humans, and cats as final hosts,

respctively. These Sarcocystis species can be identified

by the morphological features of cysts, especially the

thickness and structure of their wall. in addition to the

specificity to final hosts and the prepatent period.

Cysts of distinct species have characteristic shapes,

maximal sizes, and surface feature. Most of Sarcocystis

cyst has surface projections, whose size, shape and

arrangement in mature cysts have a constant feature

of species11l Cysts of丘 miescherianaare as large as

1.500 μm long and 200 μm wide. Their walls are 3 to

6 μm thick and appears radially striated. The villar

protrusions on the Sarcocystis wall are up to 5μm long

and l.Oμm wide7l. The cysts isolated in the present

study had the wall structure identical with出oseof S.

miescheriana.

The prepatent period of S. miescheriana reported to

be 9 to 12 days by Erber3l and 9 to 10 days by Rommel

et al.6) Sporocysts of S. miescheriana were reported to

be 12.6×9.6μm, 12.7×10.lμm, and 11.2×8.3 μmin size.

Like these literatures, the dogs fed infected meat

passed sporocysts, 12-13×9.5-10 μmin size, in 9 days

after ingestion.

Consequently，出巴 presentspecies was identical to S.

Sarcocystis miescheriana infection in pigs and wild boars in Japan 29

miescherians based on the morphological characteristics

of cysts and sporocysts as well as the final host species.

It is known that human is the final host for S.

suihominis and infected by eating undercooked cyst-

laden meat from pigs and wild boars as an intermediate

host2・4.5l_

In the present study, none of pigs and wild boars

were infected with S. suihominis. Because of the im-

portant issue in the view of meat hygiene, continuous

the investigation of Sarcocystis infection in pigs and

wild boars may be needed.

References

1) Boch, J., Mannewitz, U., Erber, M. (1978)

Sarkospridien bei Schlachtschweinen in

Suddeutschland. Berl Muench Tieraerztl

Wochenschr. 91, 106-111.

2) Dubey, J.P. (1976) A review of Sarcocystis of do-

mestic animals and of other coccidian of cats and

dogs. J. Am. Vet Med. Assoc. 169, 1061-1078.

3) Erber, M. (1977) Moglichkeiten des Nachweises

und Differenzierung vor zwei Sarcocystis Arten des

Schweines. Berl Muench. Tieraerztl. W ochenschr.

90, 480-482.

4) Heydorn, A.O. (1977) Beitrage zum Lebenszklus der

Sarkosporidien. 9. Entwicklungszyklus von

Sarcocystis suihominis n. spec. Berl. Muench.

Tieraerztl. W ochenschr. 90, 218-224.

5) Ito, S. (1985) Life cycle of Isosporan coccidian. In :

Progress in Veterinary Science 1985,. Kindai

Shupan. Tokyo. 71-105 pp.

6) Rommel, M., Heydorn, A.O., Fischle, B. and Gestrich,

R. (1974) Beitrage zum Lebenszyklus der

Sarkosporidien. 5. Weitere Endwirte der

Sarkosporidien von Rind, Schaf, und Schwein und

die Bedeutung des Zwishenwirtes fur die

Verbreitung dieser Parasitose. Berl. Muench.

Tieraerztl. Wochenschr. 87, 392-396.

7) Saito, M., Hachisu, K., Iwasaki, K., Nakajima, T.,

Watanabe, A., Moriya, H. and Itagaki, H. (1984) A

new simple method for detection of bovine Sarcocystis

cysts. J. Jpn Vet Med. Assoc. 37, 158-162.

8) Saito, M., Nakajima, T., Watanabe, A. and Itagaki,

H. (1986) Sarcocystis miescheriana infection and its

仕equencyin pigs in Jpn. J. Vet Sci. 48, 1083-1090.

9) Saito, M., Shibata, Y., Kubo, M. and Itagaki, H.

(1998) Sarcocysti miescheriana infection in wild

bo紅 s.J. Jpn. Vet Med. Assoc. 51, 679-682.

10) Seneviratana, P., Edward, A.G., DeGiusti, D.L. (1975)

Frequency of Sarcocystis spp. in Detroit, Metro-

politan area, Michigan. Am. J. Vet. Res. 36, 337-

339.

11) Tadros, W., Larrman, J.J. (1976) Sarcocystis and

related coccidian parasites : A brief general reviw

together with a discussion on some biological

aspects of their life cycles and a new proposal for

their classification. Acta Leiden. 44, 1-107.

12) Tadros, W., Larrman, J.J. (1982) Current concepts

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468 pp.

30 動物の原虫病 第28巻 第1号（2013)

豚および野生イノシシにおける Sαrcocystis感染

斉藤守弘・萩原晶代

埼玉県食肉衛生検査センター

(2012. 7. 9受付）

要旨

2010年11月から 2011年3月までに埼玉県でと殺された肥育豚および繁殖豚，それぞれ50頭について，

住肉胞子虫の感染状況を調べた．繁殖豚50頭中3頭（6%）に Sarcocystismiescherianaの感染がみら

れたが，肥育豚には観察されなかった 2010年11月から 2011年3月までに埼玉県で捕獲された野生

のイノシシ 48頭中 3頭（6.3%）に S.miescherianaの感染がみられた.S. miescherianaシストはシス

ト壁が厚く柵状構造を呈していた走査電顕では，シスト表面に長さ 4-5μmの柵状のvillarprotrusion

が観察された.S. miescheriana感染肉を犬に投与したところ 投与後9日目以降の糞便内にスポロシ

ストの排世が認められた．

動物の原虫病 Vol.28, No. 1 : 25-30, 2013

Key words : dogs, pigs, Sarcocystis, wild boars