Analysis of Parasitic Diseases Diagnosed by Tissue Biopsy Specimens at KyungHee Medical Center (1984-2005) in Seoul, Korea

According to a remarkable economic growth and improvement of hygiene, parasite infection rates have been remarkably decreasing in Korea [1]. The decrease of parasitic infections is also due to better diagnostics and treatments along with introduction of new anthelmintic medicines, such as praziquantel, mebendazole, and albendazole. In particular, soil-transmitted parasitic diseases have declined remarkably, and some of foodborne parasites have also shown a decreasing trend. However, there are slight increasing patterns in the prevalence of Clonorchis sinensis nowadays [1].

Reports associated with zoonoses have mentioned only a few cases of tissue parasitic infections and the majority of these cases dealt with single diseases based on biopsy [2,3]. South Korea, just like the rest of the world, has few reports that are relevant to tissue parasitic infections [4-8]. Therefore, in order to provide data on the trends and frequency of parasitic infections, we analyzed data of parasitic diseases diagnosed by tissue biopsy at KyungHee Medical Center (KMC) in Seoul from 1984 to 2005 (Table 1).

Table 1.

Five-year incidence of parasitic diseases diagnosed from biopsy specimens of KMC^a during the period 1984-2005

All diagnostic information for parasitic diseases was obtained from clinical and pathological records at KMC. Among 211,859 biopsy specimens submitted for histopathological examinations during 1984-2005, 150 (0.07%) were diagnosed as the parasitic infection. A total of 13 kinds of parasitic diseases were detected (Table 2). They included cysticercosis (62 cases), sparganosis (23 cases), paragonimiasis (16 cases), amebiasis (15 cases), anisakiasis (11 cases), clonorchiasis (11 cases), ascariasis (3 cases), scabies (2 cases), enterobiaisis (2 cases), trichuriasis (2 cases), leishmaniasis (1 case), taeniasis (1 case), and thelaziasis (1 case). Analytical results of parasitic diseases showed a decreasing trend from 0.12% (1984-1994) to 0.04% (1995-2005).

Table 2.

Annual incidence of parasitic diseases at KMC^a (1984-2005)

Among 62 cases identified as cysticercosis, the involved sites included the subcutaneous tissues (28 cases; 45.2%), central nervous system (27 cases; 43.5%), and the body trunk (7 cases; 11.3%). Men showed a higher infection tendency with cysticercosis than women, with a ratio of 42 : 20 (Table 3). Among 23 cases identified as sparganosis, the sites were the subcutaneous tissues (13 cases; 56.2%), lower extremities (4 cases; 17.4%), the body trunk (5 cases; 21.7%), and the pleura (1 case; 4.4%). With regard to age groups, sparganosis began to occur in the age group of the 30s, but most cases occurred in those who are the 40s or older. Out of the 16 cases indentified as paragonimiasis, the pleural involvement was in 5 cases (31.3%), whereas the lung involvement was in 4 cases (25.0%). The rest of the cases was ectopic paragonimiasis; the involved sites were the subcutaneous tissues (2 cases; 12.5%), brain (2 cases; 12.5%), mesentery (2 cases; 12.5%), and common bile duct (1 case; 6.3%). Men showed a greater infection rate of paragonimiasis than females with the ratio of 10 : 6. Out of the 15 cases identified as amebiasis, the involved sites were the rectum (6 cases; 40%), colon (5 cases; 33.3%), and liver (4 cases; 26.7%). Men have a higher infection rate of amebiasis than females (11 : 4) (Table 3). Clonorchiasis was detected in the liver (5 cases; 45.5%), gall bladder (3 cases; 27.3%), common bile duct (2 cases; 18.2%), and the duodenum (1 case; 9%). The age onset of clonorchiasis was the 30s and the age group of the 60s indicated the highest infection rate. Out of the 11 cases identified as anisakiasis, the majority of the cases were located in the stomach (10 cases; 91%) and only 1 case was detected in the ascending colon (9%).

Table 3.

Age and sex distribution of parasitic disease patients at KMC^a (1984-2005)

Out results showed a significant decreasing trend of tissue parasitic diseases at KMC especially from 1984 to 2001. However, this trend is not shown in sparganosis, amebiasis, and anisakiasis. A previous report from KMC [9] indicated increasing trends except for anisakiasis and enterobiasis during 1972 to 1983. Put together, it has been shown that tissue parasitic infections have decreased over the previous 30 years among the patients who visited KMC. A similar national trend has been reported on the prevalence of intestinal helminths among Korean people by the Korea Center for Disease Control and Prevention, which was reported by Kim et al. [1]. According to their statistics, the overall helminth egg positive rate was 41.1% in 1981, 12.9% in 1986, 3.8% in 1992, 2.4% in 1997, and 3.7% in 2004 [1]. These data indicate that helminth infections are gradually decreasing among the Korean people during the past 20 years, except in 2004.

The most common site of cysticercosis is known to be the soft tissues [6], which include subcutaneous tissues, to which our study agrees. The central nervous system (CNS) was the second frequent location of cysticercosis. When juxtaposed with the previous reports, it can be said that the incidence of cysticercosis is quite persistent [6,7,9,10], in spite that the prevalence of the adult tapeworm, Taenia solium, became negligible [1]. However, there are only a few reports of cysticercosis diagnosed by tissue biopsy after the 1990s; hence, it seems difficult to predict the nationwide trend of the prevalence of cysticercosis. Nowadays, advancements in medical technology, such as magnetic resonance imaging (MRI) and computed tomography (CT), have led to higher diagnostic and detection rates of tissue helminth infections such as cysticercosis. According to several previous reports [6,8,9], infection rates of cysticercosis were higher in women than in men. However, in our study, infection rates of cysticercosis were higher in men than in women. Our study agrees to a previous research that showed a higher allotment rate of cysticercosis in men [11].

According to several research reports from 1924 to 1991, infections by sparganum had continually occurred in Korea [7,12,13]. In our previous research [9], 10 cases of sparganosis were discovered, yet in the present study 23 cases were detected. The infection rates of paragonimiasis were relatively high with many cases reported in endemic areas from the 1950s to 2002 [7,8,14-17]. Our study detected 16 cases of paragonimiasis, which is not a small number compared with our tissue parasitoses.

Total 11 cases of clonorchiasis were found in our study, whereas 73 cases were detected in our previous research [9]. This shows that the infection rate of clonorchiasis is decreasing among the patients at KMC. By contrast, surveys in different endemic areas displayed that the egg positive rates of clonorchiasis were variable; 37.6% in Sanchong-gun in 1992 [18], 9.3% in Okcheon-gun in 2002 [19], and 34.4% in a riverside rural area of Kyongsangnam-do in 2005 [20]. These data at least suggest that clonorchiasis is one of the parasitic diseases with no decreasing tendency in endemic areas.

In conclusion, as shown in the results of parasitic infections diagnosed by tissue biopsy during the past 22 years (1984-2005) at KMC, the frequency of parasitic infections shows an evident decreasing tendency except for several zoonotic infections, including sparganosis and anisakiasis. Therefore, this study indicates that more broad researches, social awareness, and educations for prevention are necessary to further improve parasitic diseases in Korea.