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Korean J Parasitol > Volume 45(3):2007 > Article
Lee, Song, Park, Kang, Lee, Han, Kim, Shin, and Chai: A case of Diphyllobothrium latum infection with a brief review of diphyllobothriasis in the Republic of Korea

Abstract

A case of Diphyllobothrium latum infection in a 49-year old man is described, and diphyllobothriasis latum in the Republic of Korea is briefly reviewed. An incomplete strobila of a tapeworm, 95 cm in length, without scolex and neck, was spontaneously discharged in the feces of a patient. On the basis of morphologic characteristics of the worm and eggs, the worm was identified as D. latum. The patient was successfully treated with a single dose (15 mg/kg) of praziquantel. The most probable source of infection was salmon flesh according to the past history of the patient. The first case of D. latum infection was documented in 1971, and this is the 43rd recorded case in the Republic of Korea. The 43 cases were briefly reviewed. The patients' main complaints were gastrointestinal troubles, such as mild abdominal pain, indigestion, and diarrhea, and discharge of tapeworm segments in the feces. The suspected infection sources included raw or improperly cooked flesh of fresh or brackish water fish, including the perch, mullet, salmon, and trout.

INTRODUCTION

Diphyllobothrium latum is an intestinal tapeworm of mammals, such as humans, dogs, cats, foxes, and other wild canines (Beaver et al., 1984). In the Republic of Korea, the first report of D. latum infection was documented based on recovery of eggs in the feces of 2 residents in Jinju, a southern area of Korea (Kojima and Ko, 1919). After then, 18 egg positive cases were reported by other workers (Hara and Himeno, 1923). An adult tapeworm was collected for the first time from a human in 1971 and morphologically identified as D. latum (Cho et al., 1971). Until present, a total of 42 cases have been documented. The recent advancement of life quality with improvement of dietary conditions in the Republic of Korea, in particular, increased consumption of raw fish, is presumed to be a factor for an increase in D. latum infections. We report here a case of D. latum infection, and a total of 43 documented cases reported after 1971 were briefly reviewed.

CASE RECORD

A 49-year-old man visited our hospital with a segment of a tapeworm, naturally discharged in his feces. He was a resident of Seoul, without any recent history of travel abroad or to coastal areas. He reported an otherwise non-specific history except for consumption of raw salmon in autumn of 2005 at a restaurant in Seoul. He was a construction worker, with height of 157 cm and weight of 52 kg. He didn't have any special medical history.
He reported lower abdominal pain and diarrhea from February 2006, and from March of the same year, he experienced a total of 4 episodes of fecal discharge of several segments of a tapeworm, 1 to 5 m in length. CBC was in normal range without signs of anemia (WBC: 5,900/ µl, Hb: 15.8 g/dl, Hct: 45.9%, MCV: 87.9 fL, MCH: 29.6 pg, PLT: 327,000/ µl). Blood chemistry and serology were all within normal ranges.
The specimen was brought to the Department of Parasitology and Tropical Medicine, Seoul National University College of Medicine, Seoul, Korea, and was identified as D. latum according to the characteristic morphology of the worm and the eggs. The worm was creamy-white and 95 cm long without scolex and neck. Some proglottids were fixed with 10% formalin under a pressure of a glass slide. The size of a proglottid was 8.2 x 2.7 mm, and the number of proglottids was 330. Gravid proglottids stained with acetocarmine revealed a rosette-shape uterus with 4-5 times piled-up uterine loops (Fig. 1). The eggs collected from the proglottids were oval with an operculum at the anterior end and an abopercular protuberance at the posterior end, grayish brown, and 63.5 µm in average length and 42.5 µm in average width. The patient was treated with a single dose (15 mg/kg) of praziquantel, and there was no evidence of relapse during the next 9 mo.

DISCUSSION

Since 1971 when the first worm-proven D. latum case was reported in the Republic of Korea (Cho et al., 1971), the total number of cases documented so far is 43, including the present case (Table 1). All cases of D. latum and D. latum parvum type infections (Lee et al., 1994) were included, but a case of D. yonagoense infection has been excluded from this study (Lee et al., 1988). The adult worm of D. latum was not collected in the case numbers 36, 38, and 42 (Table 1); therefore, the number of worm-proven D. latum cases in the Republic of Korea becomes 40. We briefly reviewed the 43 cases in terms of epidemiological, clinical, and parasitological aspects.
The age and sex distribution of D. latum infection revealed a predominance of infection among middle-aged men, i.e., 30-49 years (Table 2), which agrees to Sohn et al. (1996). The number of males was 31 and that of females 12 (Table 2). In general, Korean men tend to eat raw fish more frequently than women, and this tendency seems to be responsible for the higher number of D. latum cases in men. With regard to the residence of the cases, the majority of the 43 patients were citizens of Seoul or metropolitan Seoul (Bucheon), and the others were citizens of or visitors to coastal or lakeside cities like Chuncheon, Ullungdo (Island), Sokcho, and Busan (Table 3).
The major symptoms complained by D. latum cases were gastrointestinal troubles, such as abdominal pain, vomiting, diarrhea, and dyspepsia in 20 cases (Table 1). Other symptoms included anemia, fatigue, anorexia, fever, and myalgia in a few cases. In a total of 17 cases, there were natural discharge of proglottids in the feces, and in 4 cases no symptoms were complained (Table 1). Except a child reported by Joo et al. (1983), there were no other cases that showed significant signs and symptoms of anemia.
Adult worms were identified in 40 of the 43 cases, and from the 40 cases a total of 46 worms were collected; 2 cases were infected with 3 worms each, 2 cases were with 2 worms, and 36 cases were with a single worm (Table 1). Among the 46 worms recovered, 21 were with scolices. The longest worm was 1,250 cm, and 13 worms were longer than 500 cm (Table 1). For D. latum, the largest size of the eggs was 72.4 x 47.2 µm, and the smallest size 59.0 x 41.0 µm. The eggs of the 30th and 31st cases, identified as D. latum parvum type infections, were 57.5 x 37.4 µm.
The medication was atabrine in 1971, and since then until 1986, either niclosamide, bithionol, or praziquantel was used. From 1987 up to present, praziquantel has been used as the drug of choice. There was no treatment failure among the 43 cases. In our case, the treatment with praziquantel in a single dose (15 mg/kg) was successful as revealed by the disappearance of eggs in the feces at 9 mo after the treatment.
As to the second intermediate hosts for D. latum, freshwater fishes, such as pikes, burbots, trouts, salmons, and perches were listed (Beaver et al., 1984). In Japan, Eguchi (1973) listed 4 salmon species as the major second intermediate hosts for D. latum, i.e., Onchorhychus masou (masu salmon), O. gorbusha (pink salmon), O. keta, and O. nerka. However, the species of the broad fish tapeworm, i.e., D. latum, transmitted by salmonid fish was put to question, and the one in Japan by O. masou and O. gorbusha was assigned as a new species D. nihonkaiense (Yamane et al., 1986), and another in Siberia transmitted by 2 salmonid fish species, O. gorbuscha and O. keta, was assigned as D. klebanovskii (Muratov and Posokhov, 1988). The Republic of Korea and Japan share the sea and fish. Therefore, human-infecting Diphyllobothrium spp. may be taxonomically similar. In particular, the worms from cases who consumed salmonid fish among the Korean patients may have been D. nihonkaiense. However, the validity of D. nihonkaiense and D. klebanovskii remains to be further clarified, and we regarded all worms as D. latum in order to avoid taxonomic confusion.
With the exception of 2 cases in which the suspected source of infection is uncertain, all cases had the history of eating raw freshwater or brackish water fish (Table 4). The number of cases that ate salmon and mullet was equally 8 (16.6%), and those that consumed perch and trout were 7 (14.6%) and 5 (10.4%), respectively (Table 4). Most of the remaining cases recalled that they had eaten any type of raw fish. Before the 1990s, perch was most frequently reported as the suspected second intermediate host in the Republic of Korea (Lee et al., 1983, 1989), but nowadays, salmon, trout, and mullet are mainly concerned (Table 1). It is regretted that there have been no reports on D. latum plerocercoid infections in fishes; studies on the life cycle of D. latum are required in the Republic of Korea.

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Fig. 1
Gravid proglottids of D. latum discharged from the present patient, acetocarmine-stained. Note 4-5 uterine loops in rosette form. × 40.
kjp-45-219-g001.jpg
Table 1.
Summary of 43 D. latum cases reported in the Republic of Korea (1971-2007)
Case No Author (year) Age (Sex) Residence/ visit Complaints Suspected source of infection Size of eggs (μm) Lengh of strobila (cm) Collection ofscolex Drug (dosage)
1 Cho et al. (1971) 50(M) Seoul Passage of proglottids Raw fishes 66.5 × 41.2 198 No Atabrine (0.9 g)
2 Min et al. (1975) 37(M) Seoul Passage of proglottids Unknown N.m.a) N.m. No Niclosamide (2.0 g)
3 Jeonget al. (1980) 14(M) Seoul Fatigue, anorexia Perch 64.3 × 41.4 685 No Bithionol (40 mg/kg)
4 Kim and Lee (1981) 26(F) Seoul Dizziness, dyspnea Sea fish 63.8 × 43.6 40 No Niclosamide (2.0 g)
5 Kim and Lee (1982) 42(M) Seoul Abd. pain Sea fishes N.m. 635 Yes Bithionol (3.0 g)
6 Song and Jung (1983) 48(M) Busan Abd. pain Perch N.m. N.m. - Niclosamide (3.0 g)
7 Lee et al. (1983) 10(M) Seoul Abd. pain Perch 64 × 45 454 Yes Bithionol (40 mg/kg)
8 48(M) Seoul Passage of proglottids Sea fish 62 × 42 30 No Niclosamide (2.0 g)
9 64(M) Seoul No symptoms Sea fish 67 × 48 320 Yes Bithionol (40 mg/kg)
10 53(F) Seoul Abd. pain, vomiting Sea fish 59 × 41 680 Yes Praziquantel (20 mg/kg)
11 23(M) Seoul Abd. pain, indigestion Perch, mullet 67 × 45 565 Yes Praziquantel (15 mg/kg)
12 Joo et al. (1983) 17(M) Seoul Passage of proglottids Salmon N.m. 1250 No Bithionol (40 mg/kg)
13 17(M) Seoul Passage of proglottids Sea fishes N.m. 854 No Bithionol (40 mg/kg)
14 6(F) Seoul Anemia Sea fishes N.m. 45-50 Yes Bithionol (40 mg/kg)
15 35(M) Seoul Diarrhea Perch, salmon N.m. 830, 850 Yes Bithionol (40 mg/kg)
16 14(M) Seoul Passage of proglottids Sea fishes N.m. 620 No Bithionol (40 mg/kg)
17 17(F) Seoul Passage of proglottids Salmon N.m. 1050 Yes Bithionol (40 mg/kg)
18 10(M) Seoul Passage of proglottids Unknown N.m. 460 No Bithionol (40 mg/kg)
19 Cho et al. (1986) 29(M) Seoul Abd. pain Sea fish 64 × 44 92 No Unknown
20 41(M) Seoul Diarrhea, constipation Salmon 62 × 43 >20 No Unknown
21 Lee et al. (1987) 14(M) Seoul No symptoms Mullet, salmon, perch 62 × 46 650 Yes Praziquantel (13 mg/kg)
22 31(M) Seoul Abd. pain, diarrhea Perch, mllet 61 × 42 300 Yes Praziquantel (13.6 mg/kg)
23 Lee et al. (1989) 20(M) Ullungdo Fever, passage of proglottids Sea fish 63.0 × 44.0 152, 123, 100 Yes (n=2) Praziquantel (10 mg/kg)
24 30(M) Ullungdo Passage of proglottids Sea fish 63.0 × 44.0 240 No Praziquantel (10 mg/kg)
25 36(M) Seoul No symptoms Fishes 63.0 × 44.0 265, 423 No Praziquantel (10 mg/kg)
26 44(M) Seoul Passage of proglottids Sea foods 63.0 × 44.0 119, 114, 85 Yes (n=3) Praziquantel (10 mg/kg)
27 41(M) Seoul Passage of proglottids Sea fish 63.0 × 44.0 N.m. Yes Praziquantel (10 mg/kg)
28 25(M) Seoul Passage of proglottids Sea fish 63.0 × 44.0 100 Yes Praziquantel (600 mg)
29 31(M) Seoul Abd. pain, dyspepsia Sea fish 63.0 × 44.0 N.m. No Praziquantel (10 mg/kg)
30 Lee et al. (1994)b) 46(F) Seoul No symptoms Trout 57.5 × 37.4 120 Yes Praziquantel (13 mg/kg)
31 22(M) Seoul Passage of proglottids Sea fish N.m. 15 No Praziquantel (10 mg/kg)
32 Ahn et al. (1996) 43(M) Chuncheon Passage of proglottids Trout 62.4 × 41.5 665 No Praziquantel (15 mg/kg)
33 39(F) Chuncheon Dyspepsia, abd. pain Trout N.m. 550 No Praziquantel (15 mg/kg)
34 Ha et al. (1997) 60(F) Unknown Abd. pain Trout (cultured) 55-70 × 45-60 50 No Praziquantel (10 mg/kg)
35 Chung et al. (1997) 35(F) Bucheon Abd. pain Mullet 72.4 × 47.2 310 Yes Praziquantel (15 mg/kg)
36 39(M) Bucheon Abd. pain, dyspepsia Mullet 67 × 45 - No Praziquantel (15 mg/kg)
37 43(F) Bucheon Dizziness, abd. pain Mullet 70.4 × 46.4 340 Yes Praziquantel (15 mg/kg)
38 43(F) Bucheon Headache, abd. pain Mullet N.m. - No Praziquantel (15 mg/kg)
39 42(M) Bucheon Abd. pain Mullet N.m. 100 No Praziquantel (15 mg/kg)
40 Jang and Cho (2000) 42(M) Chuncheon Abd. pain Trout N.m. 300 Yes Praziquantel (10 mg/kg)
41 Lee et al. (2001) 7(F) Sokcho Passage of proglottids Salmon N.m. 42 - Praziquantel (15 mg/kg)
42 35(F) Sokcho Passage of proglottids Salmon N.m. - No Praziquantel (600 mg)
43 The present study (2007) 49(M) Seoul Abd. pain, diarrhea Salmon 63.5 × 42.5 95 No Praziquantel (15 mg/kg)

a) Not measured.

b) The worms were identified as D. latum parvum type.

Table 2.
Age and sex distribution of D. latum cases reported in the Republic of Korea (1971-2007)
Age No. of cases
Male Female Total (%)
< 9 0 2 2 (4.7)
10 ~ 19 7 1 8 (18.6)
20 ~ 29 5 1 6 (13.9)
30 ~ 39 7 3 10 (23.2)
40 ~ 49 10 3 13 (30.2)
50 ~ 59 1 1 2 (4.7)
60 ~ 69 1 1 2 (4.7)
Total 31 (72.1) 12 (27.9) 43 (100.0)
Table 3.
Residence distribution of D. latum cases (1971-2007)
Residence/place of visit No. of cases (%)
Seoul 29 (67.4)
Bucheon 5 (11.6)
Chuncheon 3 (7.0)
Ullungdo 2 (4.7)
Sokcho 2 (4.7)
Busan 1 (2.3)
Unknown 1 (2.3)
Total 43 (100.0)
Table 4.
Suspected sources of infection in D. latum infection cases (1971-2007)
Source of infection No. (%) of cases
Fish (undefined) 18 (37.5)
Salmon 8 (16.6)
Mullet 8 (16.6)
Perch 7 (14.6)
Trout 5 (10.4)
Unknown 2 (4.2)
Total 48 (100.0)a)

a) Five cases recalled that they had consumed more than 1 kind of fishes.

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