[Jpn. J. Parasitol., Vol. 34, No. 4, 311-314, August, 1985]

Research Note

Trichinella spiralis in a Raccoon Dog, Nyctereutes procyonoides viverrinus, from Yamagata Prefecture, Honshu, Japan

Susumu SAITODand Tomio YAMAGUCHI2)

(Received for publication ; December 11, 1984)

Key words: Trichinella spiralis, trichinellosis, raccoon dog, natural infection, epidemiology

The first finding of Trichinella spiralis in 30. Of 20 villagers who ate the meat raw, 15 sho Japan was in 1957, when Satoh et at. (1957) wed clinical symptoms of trichinellosis. This and Ohbayashi and Satoh (1957) reported the is the first recorded outbreak of human trichi parasite in a formalin-preserved specimen of nellosis in Japan, and a strain of T. spiralis an indigenous dog which had died four years was isolated from the muscle of a dog which earlier in Sapporo, Hokkaido. Since then, T. had been fed a piece of the infected bear spiralis infection had been reported in impor meat. Thereafter, Yamaguchi et al. (1982) ted animals such as mink from the United examined the wild animals captured in nor States (Konno et al., 1957) and polar bears thern Japan from June 1974 to June 1982. from the Netherlands and Scandinavia (Satoh Of 598 wild mammals consisting of16 species et al., 1960; Sakamoto et al., 1969). and 20 birds consisting of 4 species, only 2 Spontaneous infections of T. spiralis in out of 29 Japanese black bears were found wildlife in Japan have been reported in infected with T. spiralis. A survey of trichi sables, Martes zibellina brachyura, in na infection among dogs revealed that 3 out Hokkaido (Makita et al., 1963), a black bear, of 4 were infected in Iwasaki. They had Selenactos thibetanus japonicus, in Iwasaki, eaten bones or palms of the bear which caused Aomori (Yamaguchi, 1974) and a brown bear, human trichinellosis. Ursus arctos yesoensis, in Sapporo (Ohbayashi The second outbreak, which occurred in and Yamaguchi, 1980). The infections in the Sapporo, Hokkaido, in 1980, involved 12 black bear and brown bear were responsible persons who were diagnosed as positive on the for the outbreak of human trichinellosis in basis of clinical symptoms and the results of Iwasaki and Sapporo. serological tests. They all had eaten the raw There have been three outbreaks of human meat of a brown bear served in a local restau trichinellosis in Japan. The first one, which rant. One of the patients, who was diagno occurred in 1974 in Iwasaki, Aomori, was due sed in Tokyo, was infected during a tour of to the consumption of rawmeat of a black bear Sapporo and this is the only patient who has which had been shot locally by hunters on April been found positive for larvae in muscle bi opsy in Japan (Ozawa et al., 1981). This study was supported in part by a Grant-in-Aid The third outbreak was in 1982 in Mie for Co-operative Research No. 5870013, from the Prefecture. Of the 434 people who had eaten Ministry of Education, Science and Culture, Japan. raw bear meat in a local restaurant in Yok- i:> Department of Parasitology, Yamagata Univer sity School of Medicine, Yamagata City, Japan, ; kaichi, 60 were diagnosed as positive for tri 2) Department of Parasitology, Hirosaki University chinellosis. The source of the bear meat was School of Medicine, Hirosaki City, Japan. suspected to be Ohya-cho, Hyogo Prefecture.

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Fig. 1 Excysted and coiled larvae of Trichinella spiralis isolated by artificial digestion from the muscle of a raccoon dog. Fig. 2 A larva of Trichinella spiralis encysted in the striated muscle fibers of a raccoon dog.

At present, however, it is uncertain because was made to detect the larvae under a dissecting the restaurant owner obtained the meat from microscope and many tightly coiled nematode a wholesaler. This wholesaler, in turn, obta larvae were found (Fig. 1). Meanwhile, ined the bear meat, wild boar meat, venison, encysted larvae were also found in the etc., from various sources, including local hun muscle by compression procedure (Fig. 2). ters and also his father in Hyogo Prefecture. The cysts were ellipsoidal in shape, and the It happened that the Quarantine Section of size of 30 cysts measured was 260-420 (av. the Kobe Port Authority, Hyogo Prefecture, 349.2) pm in long axis by 204-299 (av. 249.1) did detect Trichinella infected bear meat jum in short axis. The cyst wall was very imported from mainland China. Further thin and many round fat cells were accumula investigation revealed that the importer of ted at both poles of the cyst, but no calcifi the infected bear meat was the father of the cation was found in the cyst. Excysted larvae aforementioned wholesaler. Therefore, the fixed in 70 % hot ethanol were used for the imported bear meat from mainland China measurement. The size of 20 larvae measu might have been involved in the outbreak, but red was 755-925 (av. 866.0) //m in length and there is no definite proof of this. 32-39 (av. 36.6) ftm in maximum width. As noted above, bears have so far been The females were somewhat longer than the thought to be the only animal to harbour T. males in body length. The oesophagus was spiralis and the meat to be the infection slender and very long and measured 505-650 source of trichinellosis in Japan. (av. 596.7) /urn in length. The oesophagus, The present paper is concerned with the except for the anterior part, was covered with first record of natural infection of T. spiralis stichosomes (350-450 [tm, av. 414.6 fim in in a raccoon dog in Japan. length), a compact cord of linerly arranged The male raccoon dog, skinned weight gland-like cells called "stichocytes". The 1.95 kg, was killed on March 24, 1984 in a oesophagus was followed by the midgut and traffic accident on the mountain road named then by the hindgut or rectum which measur Kitsunegoe-kaido, which leads from the sou ed 23-30 (av. 25.6) //m in length in females thwest border of Yamagata City to Shirataka and 40-55 (av. 47 A) //m in males. The mor Town. About 50 gms of muscle were collec phological characteristics as described above ted from each part of the body, minced and agree well with those of the in tram uscu Jar digested for one hour at 37°C in artificial larvae of Trichinella spiralis. gastric juice consisting of 500 mg/ml pepsin The number of encysted larvae per gram (1 : 10,000) and 0.08N HC1. Observation muscle in each muscle found by the com-

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Table 1 Distribution of T. spiralis larvae in may exist in the surburbs of Yamagata City. the muscles of a raccoon dog* obtained Also, it is suggested that the trichina worm in Yamagata City (March 24, 1984) is more widely distributed than we expect among wild animals in Japan. Muscles No. larvae/g of muscle (%)

Diaphragm 152 ( 5.9) The authors are grateful to Mr. K. Ichiyama, Fore limb (L) 300 (11-7) a taxidermist, Kaminoyama City, Yamagata Prefec

Fore limb (R) 325 (12.7) ture, for providing the sample.

Hind limb (L) 308 (12.0) References Hind limb (R) 412 (16.1)

Masseter 59 ( 2.3) 1) Britov, V. A. (1968): Dinamika reaccji pa- tomorfologiczenych w miesniach swin zara- Sarcospinal 162 ( 6.3) zonych dalekowschodnim naturanym szcze- Neck 291 (11.4) pem T. spiralis. Wiad. Parazytol., 14, Abdominal 164 ( 6.4) 449-453. Intercostal 140 ( 5.5) 2) Huang, W. H. (1980): Studies on infecti Tongue 246 ( 9.6) vity of Japanese strain of Trichinella spiralis. Hirosaki Med. J., 32, 279-301 (in Japanese). * Body length : 52 cm 3) Konno, S., Ohbayashi, M. and Yamashita, Body weight skinned : 1.95 kg J. (1957) : On Trichinella spiralis found in a L : Left, R : Right mink. Tokyo Iji-shinshi, 74, 770(in Japanese). 4) Lukashenko, N. P. and Brzesky, W. W. pression procedure was: limbs, 300-412 ; (1962): Trichinellosis in wild animals in neck, 291 ; tongue, 246 ; abdomen, 164 : sa Siberia, Arctic and Far East USSR. Wiad. rcospinal, 162 ; diaphragm, 152 ; intercostal, Parazytol., 8, 589-597. 140; and masseter, 59 (Table 1). This 5) Makita, M., Yoshikawa, T. and Takahashi, H. (1963) : The fourth report of trichinosis finding is fairly consistent with the data on in Japan. Jui Chikusan Shinpo, No. 353, raccoon dogs experimentally infected with 670-673 (in Japanese). T. spiralis (Huang, 1980). 6) Ohbayashi, M. and Satoh, H. (1957): Di Natural infection with T. spiralis in ra scovery of a case of trichinosis in Japan. ccoon dogs in the USSR has been reported Jpn. J. Vet. Res., 5, 39-42. by Lukashenko and Brzesky (1962) in two 7) Ohbayashi, M. and Yamaguchi, T. (1980): regions, Tatar and Primorski Krai, and by An outbreak of trichinosis in Hokkaido, Ja Britov (1968) in the basin of the River Amur. pan. Progr. Sum. Sino-Jap. Seminar Parasit. However, they did not mention the distribution Zoon. 1980, 82-86. 8) Ozawa, E., Nakada, K., Yokogawa, M. and of the larvae in the muscle. Kobayashi, M. (1981) : A case report of tri Yamaguchi (1982) considers that T. spiralis chinosis infected in Sapporo. Inf. Inflam. has long existed among wildlife in Japan, Immun., 11, 233-240 (in Japanese). and the Japanese strain of trichina worm, 9) Sakamoto, T., Kaneta, H. and Nakagawa, the Iwasaki strain from the Japanese black S. (1969): Studies on Trichinella spiralis bear showed lower infectivity in domestic (Owen, 1835) from polar bear Thalarctos animals than the European and USA strains. martimus (Phipps). Jpn. J. Parasitol., 18 Konno et at. (1957), however, detected tri (Suppl.), 715 (in Japanese). china larvae from a mink imported from the 10) Satoh, H., Ohbayashi, M., Uemura, A. and Ida, T. (1957) : The first case of trichinosis United States, so it cannot be denied absolu in Japan. Jui Chikusan Shinpo, No. 207, tely that T. spiralis from the raccoon dog in 557-562 (in Japanese). Yamagata City may have originated from 11) Satoh, H., Nakamatsu, M., Uemura, T. and minks, which have been bred in Yamagata Ida, T. (1960) : The third case of trichino City. sis in Japan. Jui Chikusan Shinpo, No. 291, From the present observation, it is con 1274-1278 (in Japanese). cluded that an endemic area of T. spiralis 12) Yamaguchi, T. (1974): An outbreak of tri-

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chinosis in Japan. Jpn. J. Parasitol., 24 (Su- demiological aspects of trichinellosis in Ja ppl.), 57-58 (in Japanese). pan. Progr. Sum. Sino-Jap. Seminar Parasit. 13) Yamaguchi, T., Yagisawa, M., Inaba, T., Zoon; 1982, 117-124. Huang, W. H. and Ishida, K. (1982): Epi-

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