Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

6

Weeks in Review

2

Weeks to Publication
Indexed in KCI, KoreaMed, Synapse, DOAJ
Open Access, Peer Reviewed
pISSN 2288-0585 eISSN 2288-6850

Serological diagnosis of tissue-invading parasites in Korea

Original article

Choi MH. Serological diagnosis of tissue-invading parasites in Korea. Ann Clin Microbiol 2024;27:81-91.

Annals of Clinical Microbiology (Ann Clin Microbiol) 2024 June, Volume 27, Issue 2, pages 81-91. https://doi.org/10.5145/ACM.2024.27.2.5

Received on 17 May 2024, Revised on 20 May 2024, Accepted on 20 May 2024, Published on 20 June 2024.

Serological diagnosis of tissue-invading parasites in Korea

Department of Parasitology and Tropical Medicine, Institute of Endemic Diseases, Seoul National University College of Medicine, Seoul, Korea

Corresponding author: Min-Ho Choi, E-mail: mhchoi@snu.ac.kr

Abstract

Although intestinal parasites are no longer considered a significant public health concern in Korea, tissue-invading parasites continue to pose clinical challenges. The diagnosis of tissue helminthiasis by recovering worms or larvae from tissues is invasive; therefore, serodiagnosis is widely used to diagnose infections caused by tissue-invading parasites. Among the serological tests, the enzyme-linked immunosorbent assay (ELISA) is the most commonly used, and various antigens, including crude antigens, excretory-secretory antigens of helminths, and cystic fluid of larval tapeworms, are used to detect specific IgGs against parasite antigens in the sera or cerebrospinal fluid of patients. A multi-antigen ELISA was used to diagnose four major tissue parasitic infections: clonorchiasis, paragonimiasis, cysticercosis, and sparganosis. In addition to these four parasitic infections, ELISA remains a valuable diagnostic method for toxocariasis, trichinellosis, fascioliasis, echinococcosis, and other diseases. A comprehensive history of the mode of transmission of the suspected parasites and the patient’s residence in or travel to an endemic area may help in making a definitive diagnosis. For the management of patients with eosinophilia in Korea, it is essential to perform ELISA for the differential diagnosis of toxocariasis. Serological tests have the disadvantage of being unable to differentiate between past and current infections, and the possibility of cross-reactivity requires careful interpretation. It is important to note that the results of serological tests are not necessarily conclusive and should be interpreted in the context of other symptoms, as well as clinical and imaging findings.

Keywords

Helminths, Serological tests, ELISA, Korea

Introduction

With the exception of malaria, most parasitic infections are neglected tropical diseases (NTDs) that affect more than one billion individuals globally, predominantly in impoverished communities situated in tropical or subtropical regions [1]. The list of NTDs was recently expanded by the World Health Organization (WHO) to include 21 infectious diseases caused by viruses, bacteria, parasites, fungi and toxins, including 12 parasitic diseases [1]. Various stakeholders, including the WHO, developed countries, non-governmental organizations, and pharmaceutical companies, are working together to control, prevent, eliminate, and eradicate NTDs according to the NTD roadmap for 2021-2030 guided by the WHO [1].

A nationwide survey of intestinal parasitic infections conducted in Korea in 2012 revealed a prevalence of 2.6%, with Clonorchis sinensis having the highest infection rate of 1.9% [2]. Nationwide control measures for parasitic infections, such as mass stool examinations and selective drug treatment, have resulted in the successful control of soil-transmitted helminthiases, including Ascaris lumbricoides, Trichuris trichiura, and hookworms, in Korea [3]. However, parasites that live in tissues or are transmitted through food are still prevalent in Korea because of the cultural habits of eating raw fish or meat, and the diagnosis of these conditions is important. Instead of the invasive approach of obtaining worms or larvae from tissues, serodiagnosis has been developed for tissue helminthiases and is widely used to diagnose infections caused by tissue-invading parasites.

Serological tests are not as definitive as stool tests for the diagnosis of parasitic diseases. Instead, they are used as adjuncts to clinical symptoms, laboratory findings, and radiological imaging for the diagnosis of tissue-invading parasites [4,5]. The enzyme-linked immunosorbent assay (ELISA) is commonly used to detect specific IgGs against parasite antigens in the blood of suspected patients. This review discusses serological tests for the diagnosis of parasitic infections in Korea, with a special emphasis on ELISAs.

Multi-antigen ELISA

Tissue-invading parasites, including Clonorchis sinensis, Paragonimus westermani, the metacestodes of Taenia solium, and the plerocercoid larvae of Spirometra erinacei (sparganum), remain a significant public health issue in Korea. Clonorchiasis can lead to cholangiocarcinoma if left untreated, and the other abovementioned parasites are clinically significant because they can invade the nervous system and cause neurological symptoms, such as headaches, seizures, and paralysis. ELISAs have been developed to diagnose tissue-invasive parasitic infections. However, because cross-reactions between helminthiases are common, a multi-antigen ELISA that simultaneously detects antibody responses to four parasite antigens is recommended [4,5].

Two research groups in Korea have presented the results of multi-antigen ELISAs performed for over a decade (Table 1). In their analysis of ELISA results from 1993 to 2006, Lee et al. [4] (2010) found that 7.6% of 74,448 specimens were positive for antigens from any of the four tissue parasites. The antibody positivity rate showed a gradual decline from 18.7% in 1993 to 6.6% in 2006, and the positivity rate for individual parasites also gradually decreased. In contrast, Jin et al. [5] (2017) reported that 25% of 6,017 specimens from 1996-2006 were positive for one of the four parasites. The seropositivity rates for each parasite fluctuated, but slowly decreased after 2004, with considerable variation in the annual seropositivity rate, ranging from 12.1% to 35.7%.

The discrepancy in seropositivity rates between the two studies is believed to be attributable to differences in referral sources and the types and numbers of specimens analyzed. Lee et al. [4] (2010) analyzed specimens from 121 hospitals across the country, including serum, cerebrospinal fluid (CSF), or both. Approximately one-sixth of the samples were CSF samples from patients with suspected parasitic infections of the central nervous system, including the brain. In contrast, Jin et al. [5] (2017) analyzed samples from Seoul National University Hospital and its affiliated hospitals that were referred for differential diagnosis of suspected tissue helminthiases, including those affecting the liver, lungs, and central nervous system. Although there was a discrepancy in the seropositivity rates between the two studies, clonorchiasis and cysticercosis exhibited higher positivity rates than the other two helminthiases. The highest antibody positivity rates were observed in men in their 50s and 60s.

The possibility of polyparasitism and cross-reactivity should be considered [5]. If a multi-antigen ELISA yields seropositive results with more than two parasite antigens, the antigen with the strongest reaction is considered the causative infection, whereas a weak positive reaction is regarded as a cross-reaction. It is important to interpret serological test results in conjunction with other clinical symptoms and laboratory data, including radiological imaging and biopsy interpretation, to identify the causative parasitic infection.

Cross-reactions has been observed in approximately 20% of cases, mainly between helminths of the same class, such as between clonorchiasis and paragonimiasis, or between sparganosis and cysticercosis (Table 1) [4,5]. In an analysis of cases with double-positive reactions, clonorchiasis cross-reacted, in the following order, with cysticercosis, paragonimiasis, and sparganosis, while paragonimiasis cross-reacted mainly with clonorchiasis [5]. Cysticercosis cross-reacts with either clonorchiasis or sparganosis, whereas sparganosis cross-reacts with either cysticercosis or clonorchiasis [5].

Another limitation of serological tests, including ELISA, is the difficulty of differentiating between past and present infections [5]. Positive results for clonorchiasis may include both past and present infections, as clonorchiasis is the most common parasitic infection in Korea. Some cases of neurocysticercosis are not newly diagnosed, but have been diagnosed in the past and were found to be seropositive during work-up for other neurologic diseases [6].

Table 1. Comparison of analysis of multi-antigen enzyme-linked immunosorbent assay results for tissue-invading helminthiases in Korea

Clonorchiasis

Clonorchiasis is prevalent among residents of riverside areas who consume raw freshwater fish, especially in the southern areas of Korea along the Nakdong and Seomjin Rivers [7]. Although stool examination remains the gold standard for diagnosis, ELISA using crude or excretory-secretory antigens is a valuable tool for the diagnosis of clonorchiasis. To improve diagnostic accuracy, it is recommended that both stool examination and ELISAs be performed simultaneously, as most cases of clonorchiasis are more likely to be light-infected and the sensitivity of these tests may decrease [5,8].

To develop a serologic diagnostic test for clonorchiasis, a search was conducted for antigens that are sensitive to and specific for the disease [912]. ELISA using excretory-secretory antigens showed superior results, with a sensitivity of 92.5% and specificity of 93.1%, compared to 88.2% and 97.8% for ELISAs using crude antigens [8]. Antigens suitable for serodiagnosis include the 7-kDa protein of the excretorysecretory product as well as the omega-class glutathione transferases and cysteine proteinase of C. sinensis [911]. The recombinant 7-kDa protein demonstrated a sensitivity of 81.3% and a specificity of 92.6% using ELISA [11]. The sensitivities of two recombinant forms of C. sinensis omega-class glutathione transferases (rCsGSTo1 and rCsGSTo2) were 92.3% and 93.2%, respectively, with specificities of 89.7% (rCsGSTo1) and 97.6% (rCsGSTo2) [9]. Shen et al. [12] (2009) evaluated the applicability of four recombinant proteins, including a 7-kDa protein, 28-kDa cysteine protease, and 26- and 28-kDa glutathione S-transferases, for serodiagnosis. The crude antigen demonstrated the highest sensitivity (92.7%) and specificity (100%), whereas the sensitivities of the four recombinant proteins were significantly lower, with specificities exceeding 94.5%. These results suggest that a cocktail or chimeric antigen may provide a more effective serodiagnostic approach for clonorchiasis than a single recombinant antigen in ELISAs [12].

Paragonimiasis

Paragonimiais is a disease that occurs when humans consume raw or undercooked freshwater crustaceans, such as crabs and crayfish, containing metacercariae of P. westermani or when they ingest undercooked meat from paratenic hosts, such as wild boars, deer, and rodents [13]. In Korea, cases of paragonimiasis have decreased in recent years because of a decrease in the population of freshwater crustaceans caused by water pollution [4]. It is challenging to differentiate pulmonary paragonimiais from tuberculosis or lung cancer. Additionally, the patient’s symptoms, clinical findings, and laboratory findings are not easily differentiated from other diseases, which often results in the delayed diagnosis of paragonimiasis using ELISA [13]. Paragonimiasis should be included in the differential diagnosis of parasitic diseases in patients with pulmonary lesions associated with eosinophilia and/or elevated IgE levels [4]. It is common for the metacercariae of P. westermani to fail to reach the lungs during migration within the human body [14]. Instead, they become trapped in other organs, such as the brain, liver, and abdominal wall, resulting in the development of ectopic paragonimiasis, which presents diagnostic and therapeutic challenges.

Cho et al. [15] (1981) reported that an ELISA using the crude antigen of P. westermani is a highly sensitive (86%) and specific (100%) method for diagnosing paragonimiasis without cross-reactions with other parasite antigens. ELISA using recombinant P. westermani yolk ferritin demonstrated 100% sensitivity and 97.2% specificity for sera, and 97% sensitivity and 92.5% specificity for CSF [16]. This assay is highly effective for the serodiagnosis of both early and chronic cerebral paragonimiasis.

Jin et al. [5] (2017) analyzed the correlation between seropositivity and clinical diagnoses in 165 patients whose medical records were available. The results indicated that paragonimiasis showed the highest correlation rate (81.8%). Of the 685 cases of pleuropulmonary paragonimiasis analyzed over a 22-year period, Ahn et al. [13] (2021) found that only 20 tested negative by ELISA. These studies indicate that ELISA is a reliable diagnostic method for paragonimiasis.

Cysticercosis

The prevalence of taeniasis and cysticercosis in Korea has declined significantly, with an egg positive rate of 0.04% in 2012 [2]. A prevalence survey of neurocysticercosis conducted on 2,667 randomly selected patients with epilepsy from 1987 to 1990 yielded a positivity rate of 4.0% [17]. The highest prevalence (8.4%) was observed in patients residing in Cheju-do. Statistical analysis of data provided by the Health Insurance Review and Assessment Service in Korea showed a notable decrease in the number of cysticercosis cases from 642 in 2011 to 433 in 2018; however, a significant proportion of these were considered to be previous infections found during follow-up for other neurological conditions [6]. This dramatic change in the prevalence of taeniasis and cysticercosis is thought to be due to changes in pig production, improvements in sanitation and waste disposal systems, the introduction of effective anthelmintics (praziquantel), and improvements in radiological imaging.

Cystic fluid from T. solium metacestodes is the most commonly used antigen for cysticercosis ELISAs, with a sensitivity of 90.1% and a specificity of 88.5% [18]. CSF shows higher sensitivity than serum, indicating the potential benefit of using both serum and CSF in a serological test to differentiate neurocysticercosis from other neurological diseases [18]. Serological follow-up assessments for neurocysticercosis should be performed annually for at least 5 years to differentiate between patients who have been cured and those who still have chronic symptoms and slowly calcifying lesions [19,20].

Cross-reactivity may occur with other larval cestode infections, such as echinococcosis and sparganosis. These reactions are induced by several proteins that are usually high-molecular-weight proteins of T. solium metacestodes. In contrast, low-molecular-weight proteins (7-24 kDa) in cystic fluid have been shown to elicit specific antibody responses [20]. Proteomic analyses have shown that the majority of the low-molecularweight proteins may originate from two macromolecules of 120 kDa (consisting of 14-38 kDa subunits) and 150 kDa (7-15 kDa subunits) present in the cyst fluid of T. solium metacestodes [20,21]. These two glycoproteins elicit strong antibody responses against sera from patients with neurocysticercosis [20,21]. Bae et al. [21] (2008) constructed a recombinant chimeric antigen from four representative proteins (one from the 120 kDa protein and three from the 150 kDa protein) with different epitope specificities. The recombinant chimeric protein ELISA showed sensitivity comparable to that of the cystic fluid ELISA in the diagnosis of neurocysticercosis, but a markedly different specificity, with a significant reduction in cross-reactivity between neurocysticercosis and echinococcosis. Their study clearly demonstrated that recombinant chimeric antigen could replace native cystic fluid as a reliable antigen source for neurocysticercosis diagnostic platforms [21].

Sparganosis

At least 438 cases of sparganosis were documented in Korea between 1924 and 2015 [22]. The ingestion of raw or undercooked frogs, snake flesh, or other paratenic hosts, and drinking water containing cyclops infected with the procercoid larvae of S. erinacei are two common modes of human infection in Korea [22]. Sparganosis is most common in men aged > 50 years, and most cases involve subcutaneous tissue, followed by the central nervous system [22]. Since the 1980s, the number of cases diagnosed prior to surgical intervention has increased significantly because of the availability of serological and imaging diagnostics, such as ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) [22]. A crude saline extract of sparganum has been used as an antigen for ELISA. Seroepidemiological studies conducted on healthy individuals in Korea indicated that the seropositivity rates for sparganosis range from 1.7% to 4.2% [2325]. Cross-reactions have been observed in more than 50% of serum samples that are positive for sparganosis, with cysticercosis and clonorchiasis being the most common [5].

Other tissue parasitic infections

Toxocariasis

The epidemiological features of toxocariasis differ between Western and Eastern countries. In Western countries, children are more likely than adults to contract Toxocara canis infections because of their greater level of exposure to soil contaminated with T. canis eggs, which may result from geophagy, poor hygiene, or contact with dogs [26]. Conversely, adults have a higher incidence of toxocariasis than children in Eastern countries such as Korea and Japan. Adults contract toxocariasis as a food-borne infection through the consumption of raw meat or liver from animals infected with T. canis larvae [27,28].

Toxocariasis can be diagnosed based on a patient’s medical history, clinical and laboratory findings, and serological tests [27]. A commercial ELISA kit is widely used for the serodiagnosis of toxocariasis. It uses the excretory-secretory antigen derived from second-stage larvae of T. canis to detect T. canis-specific IgG with 91% sensitivity and 86% specificity [29]. Jin et al. [30] (2013) developed an ELISA using the crude antigen of T. canis larvae and showed that it has a sensitivity of 92.2% and specificity of 86.6%, which is comparable to that of a commercial ELISA kit.

The relationship between toxocariasis and patients’ place of residence, whether urban or rural, is a topic of debate in Korea. Previous studies have reported a higher prevalence of toxocariasis in rural areas than in urban areas [31,32]. In contrast, other studies have found that the seropositivity rate was approximately 5% among adults in rural areas [33], and 65.0% among healthy people with eosinophilia living in Seoul [34]. The observed discrepancies in the seroprevalence of toxocariasis with respect to residential areas are likely attributable to cultural preferences for consuming raw animal liver in Korea, rather than to the risk of exposure to T. canis eggs in the environment.

In Korea, toxocariasis is the most prevalent causative parasite in patients with suspected parasitic infections and eosinophilia, particularly in those with a history of consuming raw meat or livers of animals [27,35,36]. The seroprevalence of toxocariasis exhibits considerable variability among subjects with eosinophilia [27,28,31,3438]. The rates have ranged from 8.7% to 86.7%, with most participants exhibiting seroprevalence rates exceeding 45%. Despite considering cross-reactions and past infections, the high prevalence of antibody positivity for toxocariasis indicates that toxocariasis should be differentiated in patients presenting with eosinophilia. Regardless of the treatment, most cases of eosinophilia associated with toxocariasis have a self-limiting course with a median duration of 3 months, suggesting a 3- or 4-month follow-up interval for patients with eosinophilia [27,36].

Trichinellosis

Since the first reported case of human infection with Trichinella spiralis in 1997 [39], there have been eight documented outbreaks of human trichinellosis in Korea [4044]. These infections are transmitted through the ingestion of raw meat from wild boars or soft-shelled turtles. The diagnosis in these cases was based on the identification of T. spiralis larvae in the muscle and/or the use of ELISA with crude T. spiralis larval antigen [3944].

Fascioliasis

Humans can become infected with Fasciola hepatica, a trematode of cattle and sheep, by ingesting water or raw water vegetables contaminated with metacercariae [45]. Since the first human case reported in Korea in 1976 [46], cases have been sporadically documented [4753]. Ectopic fascioliasis is common and has been found in various organs, including the cecum [47], abdominal muscles [52], pancreas [50], and eyes [48]. Fascioliasis can be diagnosed by direct identification of worms or eggs from surgical specimens, serological tests, imaging findings, and histopathological observation [4753]. Currently, fascioliasis is mainly diagnosed by ELISA using crude antigens, excretory-secretory antigens, or recombinant antigens [5355], and less than half of the reported cases have been diagnosed by ELISA [4753].

Echinococcosis

The diagnosis of echinococcosis caused by either Echinococcus granulosus or E. multilocularis may be based on clinical findings, serological analysis, and radiological imaging techniques such as ultrasonography, CT, and MRI [56]. Most cases in Korea have been imported, with the exception of two cases in which the origin of infection was not clearly identified [57]. Consequently, a history of travel or residence in areas where echinococcosis is endemic should be investigated for diagnosis. Serological testing is useful as an adjunct to the diagnosis of echinococcosis and as a monitoring method to observe the progress of surgery or drug treatment for cystic echinococcosis [56]. The sensitivity and specificity of ELISA using the hydatid cyst fluid of E. granulosus are 91.5% and 96%, respectively, and cross-reactivity with cysticercosis or clonorchiasis has been observed [57]. The ELISA absorbance of cystic echinococcosis patients was found to be the highest with antigen B purified from sheep E. granulosus cystic fluid antigen, followed by cystic fluid antigens from humans, sheep, mice, and cows, in descending order [57]. These findings suggest that ELISA using antigen B from sheep E. granulosus cystic fluid antigen may offer an improved serodiagnostic approach.

Conclusion

ELISA is the recommended diagnostic method when a tissue-invading parasite infection is suspected. It is advisable to perform an ELISA for suspected parasitic infections in conjunction with a multi-antigen ELISA, rather than as a standalone test, to eliminate the possibility of cross-reactions. Furthermore, obtaining a comprehensive history of the transmission mode of the suspected parasites and the patient’s residence or travel to an endemic region may assist in reaching a definitive diagnosis. In Korea, in cases where eosinophilia is present in patients with suspected parasitic infections, it is crucial to perform ELISA for the differential diagnosis of toxocariasis. The results of serological tests are not necessarily conclusive and should be interpreted in the context of other symptoms, as well as clinical and imaging findings.

Ethics statement

This was not a human population study; therefore, approval by the institutional review board and informed consent were not required.

Conflicts of interest

No potential conflicts of interest relevant to this article were reported.

Funding

This study was supported by the Seoul National University Hospital.

References

1. WHO. Neglected tropical diseases. https://www.who.int/health-topics/neglected-tropicaldiseases#tab=tab_1 [Online] (last visited on 3 April 2024).

2. Choi MH, Yu JR, Hong ST. Who neglects Neglected Tropical Diseases? – Korean perspective. J Korean Med Sci 2015;30:S122-30.   

3. Hong ST, Chai JY, Choi MH, Huh S, Rim HJ, Lee SH. A successful experience of soiltransmitted helminth control in the Republic of Korea. Korean J Parasitol 2006;44:177-85.   

4. Lee MK, Hong SJ, Kim HR. Seroprevalence of tissue invading parasitic infections diagnosed by ELISA in Korea. J Korean Med Sci 2010;25:1272-6.   

5. Jin Y, Kim EM, Choi MH, Oh MD, Hong ST. Significance of serology by multi-antigen ELISA for tissue helminthiases in Korea. J Korean Med Sci 2017;32:1118-23.   

6. Kim JY, Yi MH, Yong TS. Parasitic infections and medical expenses according to health insurance review assessment claims data in South Korea, 2011-2018. PLoS One 2019;14:e0225508.   

7. Jeong YI, Shin HE, Lee SE, Cheun HI, Ju JW, Kim JY, et al. Prevalence of Clonorchis sinensis infection among residents along 5 major rivers in the Republic of Korea. Korean J Parasitol 2016;54:215-9.   

8. Choi MH, Park IC, Li S, Hong ST. Excretory-secretory antigen is better than crude antigen for the serodiagnosis of clonorchiasis by ELISA. Korean J Parasitol 2003;41:35-9.   

9. Kim JG, Ahn CS, Sripa B, Eom KS, Kang I, Sohn WM, et al. Clonorchis sinensis omegaclass glutathione transferases are reliable biomarkers for serodiagnosis of clonorchiasis and opisthorchiasis. Clin Microbiol Infect 2019;25:109.e1-.e6.  

10. Na BK, Lee HJ, Cho SH, Lee HW, Cho JH, Kho WG, et al. Expression of cysteine proteinase of Clonorchis sinensis and its use in serodiagnosis of clonorchiasis. J Parasitol 2002;88:10006.  

11. Zhao QP, Moon SU, Lee HW, Na BK, Cho SY, Kong Y, et al. Evaluation of Clonorchis sinensis recombinant 7-kilodalton antigen for serodiagnosis of clonorchiasis. Clin Diagn Lab Immunol 2004;11:814-7.   

12. Shen C, Lee JA, Allam SRA, Bae YM, Han ET, Takeo S, et al. Serodiagnostic applicability of recombinant antigens of Clonorchis sinensis expressed by wheat germ cell-free protein synthesis system. Diagn Microbiol Infect Dis 2009;64:334-9.  

13. Ahn CS, Shin JW, Kim JG, Lee WY, Kang I, Im JG, et al. Spectrum of pleuropulmonary paragonimiasis: an analysis of 685 cases diagnosed over 22 years. J Infect 2021;82:150-8.  

14. Blair D. Paragonimiasis. In: Toledo R and Fried B, eds. Digenetic trematodes. New York; Springer New York, 2014:115-52.  

15. Cho SY, Hong ST, Rho YH, Choi SY, Han YC. Application of micro-ELISA in serodiagnosis of human paragonimiasis. Korean J Parasitol 1981;19:151-6.  

16. Kim JG, Ahn CS, Kang I, Shin JW, Jeong HB, Nawa Y, et al. Cerebral paragonimiasis: clinicoradiological features and serodiagnosis using recombinant yolk ferritin. PLoS Negl Trop Dis 2022;16:e0010240.   

17. Kong Y, Cho SY, Cho MS, Kwon OS, Kang WS. Seroepidemiological observation of Taenia solium cysticercosis in epileptic patients in Korea. J Korean Med Sci 1993;8:145-52.   

18. Cho SY, Kim SI, Kang SY, Choi DY, Suk JS, Choi KS, et al. Evaluation of enzyme-linked immunosorbent assay in serological diagnosis of human neurocysticercosis using paired samples of serum and cerebrospinal fluid. Korean J Parasitol 1986;24:25-41.  

19. Cho SY, Kim SI, Kang SY. Serologic follow-up study in neurocysticercosis patients by ELISA after praziquantel treatment. Korean J Parasitol 1986;24:159-70.  

20. Ahn CS, Kim JG, Huh S, Kang I, Kong Y. Advances in serological diagnosis of Taenia solium neurocysticercosis in Korea. Genomics Inform 2019;17:e7.   

21. Bae YA, Jeong YT, Chung JY, Kim SH, Mahanta J, Feng Z, et al. A recombinant chimeric antigen toward a standardized serodiagnosis of Taenia solium neurocysticercosis. Proteomics Clin Appl 2008;2:1596-610.  

22. Kim JG, Ahn CS, Sohn WM, Nawa Y, Kong Y. Human sparganosis in Korea. J Korean Med Sci 2018;33:e273.   

23. Kong Y, Cho SY, Kang WS. Sparganum infections in normal adult population and epileptic patients in Korea: a seroepidemiologic observation. Korean J Parasitol 1994;32:85-92.  

24. Lee KJ, Bae YT, Kim DH, Deung YK, Ryang YS. A seroepidemiologic survey for human sparganosis in Gangweon-do. Korean J Parasitol 2002;40:177-80.   

25. Lee MR, Ju JW, Yang HW, Kim TS, Park MY, Cho SH. Seropositivity and identification of paramyosin for sparganosis in the Kangwon and Incheon provinces of the Republic of Korea. J Helminthol 2017;91:642-6.  

26. Glickman LT. The epidemiology of human toxocariasis. In: Lewis JW and Maizels RM, eds. Toxocara and toxocariasis: clinical, epidemiological and molecular perspectives. London; Birbeck & Sons, 1993:3-10.

27. Song HB, Lee D, Jin Y, Kang J, Cho SH, Park MS, et al. Prevalence of toxocariasis and its risk factors in patients with eosinophilia in Korea. Korean J Parasitol 2020;58:413-9.   

28. Won EJ, Kim J, Shin MG, Shin JH, Suh SP, Ryang DW. Seroepidemiology of toxocariasis and its clinical implications in Gwangju and Jeonnam-province, Korea. Ann Lab Med 2015;35:449-53.   

29. Jacquier P, Gottstein B, Stingelin Y, Eckert J. Immunodiagnosis of toxocarosis in humans: evaluation of a new enzyme-linked immunosorbent assay kit. J Clin Microbiol 1991;29:18315.   

30. Jin Y, Shen C, Huh S, Sohn WM, Choi MH, Hong ST. Serodiagnosis of toxocariasis by ELISA using crude antigen of Toxocara canis larvae. Korean J Parasitol 2013;51:433-9.   

31. Kim HS, Jin Y, Choi MH, Kim JH, Lee YH, Yoon CH, et al. Significance of serum antibody test for toxocariasis in healthy healthcare examinees with eosinophilia in Seoul and Gyeongsangnam-do, Korea. J Korean Med Sci 2014;29:1618-25.   

32. Lee JY, Yang MH, Hwang JH, Kang M, Paeng JW, Yune S, et al. The prevalence of toxocariasis and diagnostic value of serologic tests in asymptomatic Korean adults. Allergy Asthma Immunol Res 2015;7:467-75.   

33. Park HY, Lee SU, Huh S, Kong Y, Magnaval JF. A seroepidemiological survey for toxocariasis in apparently healthy residents in Gangwon-do, Korea. Korean J Parasitol 2002;40:113-7.   

34. Kim YH, Huh S, Chung YB. Seroprevalence of toxocariasis among healthy people with eosinophilia. Korean J Parasitol 2008;46:29-32.   

35. Kwon NH, Oh MJ, Lee SP, Lee BJ, Choi DC. The prevalence and diagnostic value of toxocariasis in unknown eosinophilia. Ann Hematol 2006;85:233-8.  

36. Yoon SY, Baek S, Park SY, Shin B, Kwon HS, Cho YS, et al. Clinical course and treatment outcomes of toxocariasis-related eosinophilic disorder. Medicine 2018;97:e12361.   

37. Choi D, Lim JH, Choi DC, Paik SW, Kim SH, Huh S. Toxocariasis and ingestion of raw cow liver in patients with eosinophilia. Korean J Parasitol 2008;46:139-43.   

38. Seo M and Yoon SC. A seroepidemiological survey of toxocariasis among eosinophilia patients in Chungcheongnam-do. Korean J Parasitol 2012;50:249-51.   

39. Sohn WM, Kim HM, Chung DI, Yee ST. The first human case of Trichinella spiralis infection in Korea. Korean J Parasitol 2000;38:111-5.   

40. Jeong JT, Seo M, Hong ST, Kim YK. An outbreak of trichinellosis by consumption of raw soft-shelled turtle meat in Korea. Korean J Parasitol 2015;53:219-22.   

41. Bang SH, Park JB, Chee HK, Kim JS, Ko SM, Kim WS, et al. Cardiac parasitic infection in trichinellosis associated with right ventricle outflow tract obstruction. Korean J Thorac Cardiovasc Surg 2014;47:145-8.   

42. Kim G, Choi MH, Kim JH, Kang YM, Jeon HJ, Jung Y, et al. An outbreak of trichinellosis with detection of Trichinella larvae in leftover wild boar meat. J Korean Med Sci 2011;26:1630-3.   

43. Lee SR, Yoo SH, Kim HS, Lee SH, Seo M. Trichinosis caused by ingestion of raw soft-shelled turtle meat in Korea. Korean J Parasitol 2013;51:219-21.   

44. Rhee JY, Hong ST, Lee HJ, Seo M, Kim SB. The fifth outbreak of trichinosis in Korea. Korean J Parasitol 2011;49:405-8.   

45. Han JK, Choi BI, Cho JM, Chung KB, Han MC, Kim CW. Radiological findings of human fascioliasis. Abdom Imaging 1993;18:261-4.  

46. Cho SY, Seo BS, Kim YI, Won CK, Cho SK. A case of human fascioliasis in Korea. Korean J Parasitol 1976;14:147-52.  

47. Park CI, Kim H, Ro JY, Gutierrez Y. Human ectopic fascioliasis in the cecum. Am J Surg Pathol 1984;8:73-7.  

48. Cho SY, Yang HN, Kong Y, Kim JC, Shin KW, Koo BS. Intraocular fascioliasis: a case report. Am J Trop Med Hyg 1994;50:349-53.  

49. Kim YH, Kang KJ, Kwon JH. [Four cases of hepatic fascioliasis mimicking cholangiocarcinoma]. Korean J Hepatol 2005;11:169-75.  

50. Lee OJ and Kim TH. Indirect evidence of ectopic pancreatic fascioliasis in a human. J Gastroenterol Hepatol 2006;21:1631-3.  

51. Park HJ, Choi GS, Jung M, Lee SU. Fasciola hepatica induced hepatic abscess treated with triclabendazole. Korean J Gastroenterol 2021;77:39-44.  

52. Jeong MJ, Park JK, Yu HS. Phylogenetic characteristics of Fasciola hepatica isolated from a Korean patient. Korean J Parasitol 2022;60:367-70.   

53. Kim SW and Jang BK. Toxocara canis and Fasciola hepatica co-infection leading to hepatic abscess: a case report. J Korean Med Sci 2023;38:e323.   

54. Mirzadeh A, Jafarihaghighi F, Kazemirad E, Sabzevar SS, Tanipour MH, Ardjmand M. Recent developments in recombinant proteins for diagnosis of human fascioliasis. Acta Parasitol 2021;6:13-25.  

55. Kim TY, Lee YS, Yun JH, Kim JJ, Choi WH, Oh IH, et al. A case of probable mixed-infection with Clonorchis sinensis and Fasciola sp.: CT and parasitological findings. Korean J Parasitol 2010;48:157-60.   

56. McManus DP, Gray DJ, Zhang W, Yang Y. Diagnosis, treatment, and management of echinococcosis. BMJ 2012;344:e3866.  

57. Jin Y, Anvarov K, Khajibaev A, Hong S, Hong ST. Serodiagnosis of echinococcosis by ELISA using cystic fluid from Uzbekistan sheep. Korean J Parasitol 2013;51:313-7.   

Table 1

1. WHO. Neglected tropical diseases. https://www.who.int/health-topics/neglected-tropicaldiseases#tab=tab_1 [Online] (last visited on 3 April 2024).

2. Choi MH, Yu JR, Hong ST. Who neglects Neglected Tropical Diseases? – Korean perspective. J Korean Med Sci 2015;30:S122-30.

3. Hong ST, Chai JY, Choi MH, Huh S, Rim HJ, Lee SH. A successful experience of soiltransmitted helminth control in the Republic of Korea. Korean J Parasitol 2006;44:177-85.

4. Lee MK, Hong SJ, Kim HR. Seroprevalence of tissue invading parasitic infections diagnosed by ELISA in Korea. J Korean Med Sci 2010;25:1272-6.

5. Jin Y, Kim EM, Choi MH, Oh MD, Hong ST. Significance of serology by multi-antigen ELISA for tissue helminthiases in Korea. J Korean Med Sci 2017;32:1118-23.

6. Kim JY, Yi MH, Yong TS. Parasitic infections and medical expenses according to health insurance review assessment claims data in South Korea, 2011-2018. PLoS One 2019;14:e0225508.

7. Jeong YI, Shin HE, Lee SE, Cheun HI, Ju JW, Kim JY, et al. Prevalence of Clonorchis sinensis infection among residents along 5 major rivers in the Republic of Korea. Korean J Parasitol 2016;54:215-9.

8. Choi MH, Park IC, Li S, Hong ST. Excretory-secretory antigen is better than crude antigen for the serodiagnosis of clonorchiasis by ELISA. Korean J Parasitol 2003;41:35-9.

9. Kim JG, Ahn CS, Sripa B, Eom KS, Kang I, Sohn WM, et al. Clonorchis sinensis omegaclass glutathione transferases are reliable biomarkers for serodiagnosis of clonorchiasis and opisthorchiasis. Clin Microbiol Infect 2019;25:109.e1-.e6.

10. Na BK, Lee HJ, Cho SH, Lee HW, Cho JH, Kho WG, et al. Expression of cysteine proteinase of Clonorchis sinensis and its use in serodiagnosis of clonorchiasis. J Parasitol 2002;88:10006.

11. Zhao QP, Moon SU, Lee HW, Na BK, Cho SY, Kong Y, et al. Evaluation of Clonorchis sinensis recombinant 7-kilodalton antigen for serodiagnosis of clonorchiasis. Clin Diagn Lab Immunol 2004;11:814-7.

12. Shen C, Lee JA, Allam SRA, Bae YM, Han ET, Takeo S, et al. Serodiagnostic applicability of recombinant antigens of Clonorchis sinensis expressed by wheat germ cell-free protein synthesis system. Diagn Microbiol Infect Dis 2009;64:334-9.

13. Ahn CS, Shin JW, Kim JG, Lee WY, Kang I, Im JG, et al. Spectrum of pleuropulmonary paragonimiasis: an analysis of 685 cases diagnosed over 22 years. J Infect 2021;82:150-8.

14. Blair D. Paragonimiasis. In: Toledo R and Fried B, eds. Digenetic trematodes. New York; Springer New York, 2014:115-52.

15. Cho SY, Hong ST, Rho YH, Choi SY, Han YC. Application of micro-ELISA in serodiagnosis of human paragonimiasis. Korean J Parasitol 1981;19:151-6.

16. Kim JG, Ahn CS, Kang I, Shin JW, Jeong HB, Nawa Y, et al. Cerebral paragonimiasis: clinicoradiological features and serodiagnosis using recombinant yolk ferritin. PLoS Negl Trop Dis 2022;16:e0010240.

17. Kong Y, Cho SY, Cho MS, Kwon OS, Kang WS. Seroepidemiological observation of Taenia solium cysticercosis in epileptic patients in Korea. J Korean Med Sci 1993;8:145-52.

18. Cho SY, Kim SI, Kang SY, Choi DY, Suk JS, Choi KS, et al. Evaluation of enzyme-linked immunosorbent assay in serological diagnosis of human neurocysticercosis using paired samples of serum and cerebrospinal fluid. Korean J Parasitol 1986;24:25-41.

19. Cho SY, Kim SI, Kang SY. Serologic follow-up study in neurocysticercosis patients by ELISA after praziquantel treatment. Korean J Parasitol 1986;24:159-70.

20. Ahn CS, Kim JG, Huh S, Kang I, Kong Y. Advances in serological diagnosis of Taenia solium neurocysticercosis in Korea. Genomics Inform 2019;17:e7.

21. Bae YA, Jeong YT, Chung JY, Kim SH, Mahanta J, Feng Z, et al. A recombinant chimeric antigen toward a standardized serodiagnosis of Taenia solium neurocysticercosis. Proteomics Clin Appl 2008;2:1596-610.

22. Kim JG, Ahn CS, Sohn WM, Nawa Y, Kong Y. Human sparganosis in Korea. J Korean Med Sci 2018;33:e273.

23. Kong Y, Cho SY, Kang WS. Sparganum infections in normal adult population and epileptic patients in Korea: a seroepidemiologic observation. Korean J Parasitol 1994;32:85-92.

24. Lee KJ, Bae YT, Kim DH, Deung YK, Ryang YS. A seroepidemiologic survey for human sparganosis in Gangweon-do. Korean J Parasitol 2002;40:177-80.

25. Lee MR, Ju JW, Yang HW, Kim TS, Park MY, Cho SH. Seropositivity and identification of paramyosin for sparganosis in the Kangwon and Incheon provinces of the Republic of Korea. J Helminthol 2017;91:642-6.

26. Glickman LT. The epidemiology of human toxocariasis. In: Lewis JW and Maizels RM, eds. Toxocara and toxocariasis: clinical, epidemiological and molecular perspectives. London; Birbeck & Sons, 1993:3-10.

27. Song HB, Lee D, Jin Y, Kang J, Cho SH, Park MS, et al. Prevalence of toxocariasis and its risk factors in patients with eosinophilia in Korea. Korean J Parasitol 2020;58:413-9.

28. Won EJ, Kim J, Shin MG, Shin JH, Suh SP, Ryang DW. Seroepidemiology of toxocariasis and its clinical implications in Gwangju and Jeonnam-province, Korea. Ann Lab Med 2015;35:449-53.

29. Jacquier P, Gottstein B, Stingelin Y, Eckert J. Immunodiagnosis of toxocarosis in humans: evaluation of a new enzyme-linked immunosorbent assay kit. J Clin Microbiol 1991;29:18315.

30. Jin Y, Shen C, Huh S, Sohn WM, Choi MH, Hong ST. Serodiagnosis of toxocariasis by ELISA using crude antigen of Toxocara canis larvae. Korean J Parasitol 2013;51:433-9.

31. Kim HS, Jin Y, Choi MH, Kim JH, Lee YH, Yoon CH, et al. Significance of serum antibody test for toxocariasis in healthy healthcare examinees with eosinophilia in Seoul and Gyeongsangnam-do, Korea. J Korean Med Sci 2014;29:1618-25.

32. Lee JY, Yang MH, Hwang JH, Kang M, Paeng JW, Yune S, et al. The prevalence of toxocariasis and diagnostic value of serologic tests in asymptomatic Korean adults. Allergy Asthma Immunol Res 2015;7:467-75.

33. Park HY, Lee SU, Huh S, Kong Y, Magnaval JF. A seroepidemiological survey for toxocariasis in apparently healthy residents in Gangwon-do, Korea. Korean J Parasitol 2002;40:113-7.

34. Kim YH, Huh S, Chung YB. Seroprevalence of toxocariasis among healthy people with eosinophilia. Korean J Parasitol 2008;46:29-32.

35. Kwon NH, Oh MJ, Lee SP, Lee BJ, Choi DC. The prevalence and diagnostic value of toxocariasis in unknown eosinophilia. Ann Hematol 2006;85:233-8.

36. Yoon SY, Baek S, Park SY, Shin B, Kwon HS, Cho YS, et al. Clinical course and treatment outcomes of toxocariasis-related eosinophilic disorder. Medicine 2018;97:e12361.

37. Choi D, Lim JH, Choi DC, Paik SW, Kim SH, Huh S. Toxocariasis and ingestion of raw cow liver in patients with eosinophilia. Korean J Parasitol 2008;46:139-43.

38. Seo M and Yoon SC. A seroepidemiological survey of toxocariasis among eosinophilia patients in Chungcheongnam-do. Korean J Parasitol 2012;50:249-51.

39. Sohn WM, Kim HM, Chung DI, Yee ST. The first human case of Trichinella spiralis infection in Korea. Korean J Parasitol 2000;38:111-5.

40. Jeong JT, Seo M, Hong ST, Kim YK. An outbreak of trichinellosis by consumption of raw soft-shelled turtle meat in Korea. Korean J Parasitol 2015;53:219-22.

41. Bang SH, Park JB, Chee HK, Kim JS, Ko SM, Kim WS, et al. Cardiac parasitic infection in trichinellosis associated with right ventricle outflow tract obstruction. Korean J Thorac Cardiovasc Surg 2014;47:145-8.

42. Kim G, Choi MH, Kim JH, Kang YM, Jeon HJ, Jung Y, et al. An outbreak of trichinellosis with detection of Trichinella larvae in leftover wild boar meat. J Korean Med Sci 2011;26:1630-3.

43. Lee SR, Yoo SH, Kim HS, Lee SH, Seo M. Trichinosis caused by ingestion of raw soft-shelled turtle meat in Korea. Korean J Parasitol 2013;51:219-21.

44. Rhee JY, Hong ST, Lee HJ, Seo M, Kim SB. The fifth outbreak of trichinosis in Korea. Korean J Parasitol 2011;49:405-8.

45. Han JK, Choi BI, Cho JM, Chung KB, Han MC, Kim CW. Radiological findings of human fascioliasis. Abdom Imaging 1993;18:261-4.

46. Cho SY, Seo BS, Kim YI, Won CK, Cho SK. A case of human fascioliasis in Korea. Korean J Parasitol 1976;14:147-52.

47. Park CI, Kim H, Ro JY, Gutierrez Y. Human ectopic fascioliasis in the cecum. Am J Surg Pathol 1984;8:73-7.

48. Cho SY, Yang HN, Kong Y, Kim JC, Shin KW, Koo BS. Intraocular fascioliasis: a case report. Am J Trop Med Hyg 1994;50:349-53.

49. Kim YH, Kang KJ, Kwon JH. [Four cases of hepatic fascioliasis mimicking cholangiocarcinoma]. Korean J Hepatol 2005;11:169-75.

50. Lee OJ and Kim TH. Indirect evidence of ectopic pancreatic fascioliasis in a human. J Gastroenterol Hepatol 2006;21:1631-3.

51. Park HJ, Choi GS, Jung M, Lee SU. Fasciola hepatica induced hepatic abscess treated with triclabendazole. Korean J Gastroenterol 2021;77:39-44.

52. Jeong MJ, Park JK, Yu HS. Phylogenetic characteristics of Fasciola hepatica isolated from a Korean patient. Korean J Parasitol 2022;60:367-70.

53. Kim SW and Jang BK. Toxocara canis and Fasciola hepatica co-infection leading to hepatic abscess: a case report. J Korean Med Sci 2023;38:e323.

54. Mirzadeh A, Jafarihaghighi F, Kazemirad E, Sabzevar SS, Tanipour MH, Ardjmand M. Recent developments in recombinant proteins for diagnosis of human fascioliasis. Acta Parasitol 2021;6:13-25.

55. Kim TY, Lee YS, Yun JH, Kim JJ, Choi WH, Oh IH, et al. A case of probable mixed-infection with Clonorchis sinensis and Fasciola sp.: CT and parasitological findings. Korean J Parasitol 2010;48:157-60.

56. McManus DP, Gray DJ, Zhang W, Yang Y. Diagnosis, treatment, and management of echinococcosis. BMJ 2012;344:e3866.

57. Jin Y, Anvarov K, Khajibaev A, Hong S, Hong ST. Serodiagnosis of echinococcosis by ELISA using cystic fluid from Uzbekistan sheep. Korean J Parasitol 2013;51:313-7.