[An Epidemiological Note On The Taeniasis In Korea]

Taenia asiatica: Historical overview of taeniasis and cysticercosis with molecular characterization

Asian Taenia is a human-infecting Taenia tapeworm known as Taenia asiatica following morphological examination of adult and larval stages of the tapeworm by Eom and Rim (1993). The life cycle of T. asiatica differs from that of T. saginata in its intermediate host (pigs versus cattle) as well as in the infected organs (liver versus muscle). T. asiatica can be differentiated from T. solium and T. saginata by examination of morphological characteristics such as the scolex, mature and gravid proglottids in the adult stage, and the scolex and bladder surface in the larval stage. T. asiatica has been identified in Korea, Taiwan, the Philippines, China, Thailand, Indonesia, Vietnam, Japan, Lao PDR, Nepal and India. The molecular tools employed for T. asiatica identification have been developed to differentiate T. asiatica from other human-infecting Taenia tapeworms based on genetic information such as nucleotide sequence of mitochondrial genes, nuclear ribosomal genes and nuclear genes that lead to development of the subsequent molecular techniques, such as PCR-RFLP, PCR-RAPD, BESST-base, LAMP and qPCR. Investigation of the phylogenetic relationships among human Taenia species revealed that T. asiatica is a sister species with T. saginata, which is genetically more similar than other Taenia species in terms of the nucleotide sequences of cox1, nad1 and 28S rDNA. The mitochondrial genomes of human Taenia tapeworms comprise 13,703bp (T. asiatica), 13,670bp (T. saginata) and 13,709bp (T. solium), and contain 36 genes including 12 protein-coding genes, 2 ribosomal RNAs (rRNAs, a small and a large subunit), and 22 transfer RNAs (tRNAs). Sequence differences in the full genome of T. asiatica and T. saginata mitochondria is 4.6%, while T. solium differs by 11%. Hox gene orthology in T. asiatica was established by comparative analysis with Platyhelminthes Hox genes. T. asiatica Hox revealed six Hox orthologs including two lab/Hox1, two Hox3, one Dfd/Hox4 and one Lox/Lox4. Hybridization between T. asiatica and T. saginata was definitely observed in these species which are sympatrically endemic in the regions of Korea, Thailand, China and Lao PDR. Comparative analyses of T. asiatica, T. saginata and T. solium genomes were also reported with genome features. Taenia asiaticus nomen novum was proposed for T. asiaticaEom and Rim, 1993 which is a homonym of T. asiatica Linstow, 1901 (Davaineidae).

Human taeniasis in the Republic of Korea: hidden or gone?

History and current status of human taeniasis in the Republic of Korea, due to Taenia solium, Taenia asiatica, and Taenia saginata, are briefly reviewed. Until the 1980s, human taeniasis had been quite common in various localities of Korea. A study from 1924 reported 12.0% egg prevalence in fecal examinations. Thereafter, the prevalence of Taenia spp. ranged from 3% to 14% depending on the time and locality. Jeju-do, where pigs were reared in a conventional way, was the highest endemic area of taeniasis. An analysis of internal transcribed spacer 2 and mitochondrial cytochrome c oxidase 1 genes of 68 taeniasis cases reported from 1935 to 2005 in Korea by a research group revealed the relative occurrence of the 3 Taenia spp. as follows: T. solium (4.4%), T. asiatica (75.0%), and T. saginata (20.6%). However, national surveys on intestinal helminths conducted every 5 years on randomly selected people revealed that the Taenia egg prevalence dropped from 1.9% in 1971 to 0.02% in 1997 and finally to 0.0% in 2004. With the exception of 3 egg-positive cases reported in 2008 and 2 worm-proven cases in 2011, no more cases have been officially recorded. Based on these surveys and also on other literature, it can be concluded that taeniasis has virtually disappeared from Korea, although a few sporadic cases may remain hidden. Human cysticercosis is also expected to disappear within a couple of decades in Korea.

Pig as a favorable animal for Taenia saginata asiatica infection

The epidemiology of Taenia saginata in some parts of Asia is confusing, in that beef does not appear to be the source of infection. In some areas, beef is either not available or not eaten raw, whereas pork at times is eaten uncooked. In light of this situation, we have exposed pigs and other animals to infection with strains of T. saginata to establish their ability to serve as intermediate hosts. Eggs of Taiwan Taenia, Korea Taenia, Indonesia Taenia, Thailand Taenia, Philippines Taenia, Ethiopia Taenia, and Madagascar Taenia were fed to 83 pigs of three strains: 43 Small-Ear Miniature (SEM), 34 Landrace Small-Ear Miniature (L-SEM), and 6 Duroc-Yorkshire-Landrace (DYL). We also fed the eggs to 10 Holstein calves, 17 Sannean goats, and 4 monkeys (Macaca cyclopis). We succeeded in infecting SEM (infection rate 88%, cysticercus recovery rate 19.1%), L-SEM (83%, 1.1%), and DYL (100%, 0.3%) pigs with Taiwan Taenia; SEM (100%, 1.7%), L-SEM (100%, 5.6%), and DYL (100%, 0.06%) pigs with Korea Taenia; SEM (100%, 22%) and L-SEM (100%, 1.6%) pigs with Indonesia Taenia; SEM (75%, 0.06%) pigs with Thailand Taenia SEM (100%, 11%) pigs with Philippines Taenia; SEM (80%, 0.005%) pigs with Ethiopia Taenia; SEM (100%, 0.2%) pigs with Madagascar Taenia. Holstein calves became infected with Taenia from Taiwan (100%, 1.1%), Korea (100%, 0.03%), Thailand (100%, 0.2%), and the Philippines (100%, 6%); however, the cysticerci of Taenia from Korea, Thailand, and the Philippines were degenerated and/or calcified. Sannean goats became infected with Taenia from Taiwan (33%, 0.01%) and Korea (50%, 0.02%), while monkeys became infected with Taenia from Taiwan (50%, 0.01%). However, the cysticerci were degenerated and/ or calcified. Therefore, these strains of pig seem to be favorable animal models for experimental studies of T. saginata-like tapeworms, with the SEM pig the most favorable.

Epidemiological understanding of Taenia tapeworm infections with special reference to Taenia asiatica in Korea

In endemic areas of Taenia tapeworms in Korea, most of the reports showed that T. saginata was dominant over T. solium, but eating pigs is the dominant habit over eating cattle. Why do they have more T. saginata despite lower consumption of beef? This problem actually has long been recognized but until recently there has been no intensive trial to give a scientific explanation on this epidemiological enigma. By summing up the data published between the years 1963 and 1999, the ratio of armed versus unarmed tapeworms in humans was estimated at approximately 1:5. The ratio of pig-eaters versus cattle-eaters, however, was approximately 5:1. This inconsistency could be explained with the recently described T. asiatica, which infects humans through the eating of pig's viscera. We re-evaluate the importance of the consumption of visceral organ of pigs. leading us to an improved epidemiological understanding of the T. asiatica infection together with co-existing T. saginata and T. solium in Korea.

Eating habits of East Asian people and transmission of taeniasis

In order to understand the role of raw meat and viscera eating habits in the transmission of taeniasis in Asian countries, 1502 infected aborigines in ten mountainous districts/towns of six counties in Taiwan, 58 infected persons in two villages on Cheju Island, Korea, and 97 cases in Ambarita District on Samosir Island, North Sumatra, Indonesia were studied during the field surveys. All infected Taiwan aborigines had the habit of eating raw meat and viscera of wild and/or domestic animals. Among these aborigines, 73% ate wild boar, 66% flying squirrel, 65% wild goat, 56% muntjac, 49% wild rats, 46% monkey, 38% hare, 20% civet-cats, 18% weasel, 17% pheasant, 14% squirrel, 4% grouse, 1% deer, 1% snake, less than 1% bamboo partridge, less than 1% frog, less than 1% bear, less than 1% dog, and less than 1% fox. Of the 58 infected persons with Taenia on Cheju Island, Korea, 72% ate raw meat and/or viscera of pig and cattle, 19% raw pork only, and 9% raw beef only. Among 12 infected persons infected with T. saginata-like tapeworms, 7 had eaten raw pork, 2 raw beef and pork and 3 raw pork. Almost all of the 97 cases of taeniasis on Samosir Island of North Sumatra, Indonesia, had eaten only undercooked pork. Eleven of 15 cases were found to be infected with T. saginata-like tapeworms. Eating habits observed suggest an unusual way of transmission of Taenia in East Asia.

Experimental studies of Korea Taenia (Cheju strain) infection in domestic animals

In the present study, one DYL pig (five-day old), four L-SEM pigs (37-day old), three SEM pigs (44-day old), one Holstein calf (eight-day old) and two Sannean goats (five-day old) were each fed 1000, 30,000, or 380,000 eggs of the Korea Taenia (Cheju strain) and were sacrificed 16-105 days after inoculation. All DYL, L-SEM, and SEM pigs and the Holstein calf were susceptible to Korea Taenia, and one of the two Sannean goats became infected. The cysticerci recovery rates for L-SEM, SEM and DYL pigs, Holstein calf, and Sannean goat were 5.6, 1.7, 0.06, 0.03 and 0.02% respectively. Cysticerci were recovered only from the livers of the infected animals, and more cysticerci were found in the parenchyma (51%) than on the surface of the liver (49%). Immature cysticerci were first observed on day 16 after infection, mature ones on day 29, and degenerated or calcified cysticerci on day 30. Inoculation of a huge number (380,000) of Korea Taenia eggs lead to early degeneration or calcification of the cysticerci. The length, the width, and the diameters of protoscolex, rostellum, and sucker of the cysticerci were largely proportional to the period of inoculation. The measurements and patterns of the hooklets indicate that Korea Taenia is very similar to Taiwan Taenia but is different from T. saginata and T. solium. The results of the present study provide evidence that Korea Taenia and Taiwan Taenia may be of the same species.

Imunological characterization of antigens from cysticercus and sparganum and their application to immunodiagnosis 1. Immunological characteristics of crude antigenic components from Cysticercus cellulosae

We studied the serological reaction between various antigenic components from Cysticercus cellulosae and IgG antibodies in sera of cysticercosis, sparganosis, hydatidosis patients and normal humans by ELISA and EITB. In serological tests by ELISA, we recognized cross reaction of Cysticercus antigenic components with IgG antibodies in heterologous sera such as sparganosis and hydatidosis patients or normal humans. The crude antigenic components of Cysticercus showed lower ELISA sensitivity in homologous sera from cysticercosis patients than heterologous sera from hydatidosis patients. A total of 31 polypeptide bands with 260 KDa-22 KDa molecular weights were detected by SDS-PAGE, and 11 of them showed strong intensity. Total 22 components of them were recognized by IgG antibodies in cysticercosis patients sera. However, 12 of them were recognized also by normal human sera, 11 were by sparganosis sera, and 21 were by hydatidosis patients sera. The crude antigenic components of 104 KDa, 82 KDa, 72 KDa, 59 KDa and 34 KDa molecular weights were nonspecific ones, which cross-reacted with sera of either cysticercosis, sparganosis, hydatidosis patients or normal humans.

[A Study On The Intestinal Helminths Of The Patients In A Leprosarium In Korea]

A total of 2,026 leprosy patients of the National Sorokdo Hospital was examined their intestinal parasites by cellophane thick smear method in January 1983. The egg positive cases of Taenia spp. were treated with bithionol and the segments of Taenia were collected for species identification. The results were as follows: 1. Total egg positive rate of any kind helminth was 78.2 % and cumulative total was 85.2 %. The egg positive rate for each helminth was as follow; Taenia spp. 3.4 %, Ascaris lumbricoides 4.5 %, Trichuris trichiura 72.l %, Clonorchis sinensis 2.8 % and other 0.05 %. 2. A total of 66 Taenia egg positive cases was treated; out of them proglottids of Taenia were collected from 26 cases. All of the collected worms were identified as T. saginata. The results revealed significantly high egg positive rate of T. trichiura. However, A. lumbricoides was found to be controlled considerably by repeated chemotherapy during past 3 years. If chemotherapeutic agent is replaced with oxantel-pyrantel tablet, better result is expected. No clue was found for prevalence of T. solium from both human and the pig in the island.

Therapeutic Trial Of Praziquantal (Embay 8440; Biltricide(R)) On The Dermal And Cerebral Human Cysticercosis

A total of 28 adult cases who were confirmed cysticercosis with or without cerebral involvements were treated with praziquantel at the daily dose of 3 x 25 mg/kg for 3 to 7 consecutive days and was evaluated for tolerance and therapeutic effects in the trials clinically performed.The assessment of drug efficacy of praziquantel in the dermal cysticercosis was made by comparing the numbers of cysticercus nodules and histopathological findings of the biopsied parasites by means of light, scanning and transmission electron microscope. In the cerebral cysticercosis, the assessment was considered by the frequency of the episodes of convulsive seizure before and after treatment with praziquantel and by the findings of the disapearance or decreased densities of the lesions in C.T. scan in comparison with those of before and after treatment. The results were as follows: 1. The cysticerci in the subcutaneous tissues began to disappear within one month of drug administration of 3 x 25 mg/kg praziquantel over 3 to 7 days. Within 3 to 6 months most of the cysticerci had disappeared, although in some case a small number of cysticercus nodules remained even one year after treatment. 2. Histological observation of the cysticerci biopsied at different times during the course of treatment revealed that morphological changes were already taking place within two weeks after the treatment. At the early stage of the treatment, small vacuoles were scattered along the basement layer in the tegumental syncytium of the scolex and neck regions. In the scanning electron microscopic observation, marked surface changes were present in the neck region with many bleb-like structures formed by the bursting of the large vacuoles in the tegumental syncytium. In the specimens biopsied at 2 or 5 weeks after treatment, the degenerations and necrosis of the tegumental syncytium were seen in all parts of cysticercus. 3. In 12 cases of cerebral cysticercosis treated with praziquantel at the daily dose of 3 x 35 mg/kg for 3 or 4 consecutive days, there were no ceasing of the convulsive seizures during the 6 months follow-up. Among them 9 cases were given again the same doses of the drug for 4 or 7 days. In 7 of 9 cases, no more convulsive seizure was experienced over one or two years after the second time. At the same treatment the lesions of the brain C.T. scan disappeared, decreasd in size or calcified after treatment. In other 3 cerebral cysticercosis cases, complete cure was also obtained after the oral medication of praziquantel at the daily dose of 3 x 25 mg/kg for 7 consecutive days. 4. In the treatment of cerebral cysticercosis with praziquantel, it was found that the concomitant oral medication of dexamethasone during the course of treatment was effective for preventing and minimizing the side-effects.