Genetic Identification of Spirometra decipiens Plerocercoids in Terrestrial Snakes from Korea and China

Human sparganosis is a zoonotic disease caused by infection with larval forms (procercoid/plerocercoid) of Spirometra spp. The purpose of this study was to identify Spirometra spp. of infected snakes using a multiplex PCR assay and phylogenetic analysis of mitochondrial DNA sequence data from the spargana of terrestrial snakes obtained from Korea and China. A total of 283 snakes were obtained that included 4 species of Colubridae comprising Rhabdophis tigrinus tigrinus (n=150), Dinodon rufozonatum rufozonatum (n=64), Elaphe davidi (n=2), and Elaphe schrenkii (n=7), and 1 species of Viperidae, Agkistrodon saxatilis (n=60). The snakes were collected from the provinces of Chungbuk, Chungnam, and Gyeongbuk in Korea (n=161), and from China (n=122). The overall infection rate with spargana was 83% (235/283). The highest was recorded for D. rufozonatum rufozonatum (100%), followed by A. saxatilis (85%) and R. tigrinus tigrinus (80%), with a negative result for E. davidi (0%) and E. schrenkii (0%). The sequence identities between the spargana from snakes (n=50) and Spirometra erinaceieuropaei (KJ599680) or S. decipiens (KJ599679) control specimens were 90.8% and 99.2%, respectively. Pairwise genetic distances between spargana (n=50) and S. decipiens ranged from 0.0080 to 0.0107, while those between spargana and S. erinaceieuropaei ranged from 0.1070 to 0.1096. In this study, all of the 904 spargana analyzed were identified as S. decipiens either by a multiplex PCR assay (n=854) or mitochondrial cox1 sequence analysis (n=50).

Plerocercoids of Nybelinia surmenicola (Cestoda: Tentacularidae) in Squids, Todarodes pacificus, from East Sea, the Republic of Korea

A visceral helminth of the squid, Todarodes pacificus, is reported from the East Sea, the Republic of Korea. Total 39 squid samples were purchased from a fish market in Jumunjin-eup, Gangneung-si (City) from August 2014 to July 2015 and were examined for helminth parasites with naked eyes and under a stereomicroscope after opening the abdominal cavity with a pair of scissors. Whitish larval worms were mainly found in the stomach and abdominal cavity of the squid. They were detected in 25 (64.1%) out of 39 squids examined, and the infection density was 7 larvae per infected squid. Spatula-shaped larvae were 8.2×2.0 mm in average size, round to slightly flattened anteriorly, with round hatching posteriorly, and had characteristic 4 tentacles with numerous hooklets in the scolex. The larvae were identified as the plerocercoid stage of Nybelinia surmenicola by their morphological features. This finding represents a new host record and the first report of N. surmenicola infection in T. pacificus squids from the east coast of Korea.

Mass Death of Predatory Carp, Chanodichthys erythropterus, Induced by Plerocercoid Larvae of Ligula intestinalis (Cestoda: Diphyllobothriidae)

We describe here the mass death of predatory carp, Chanodichthys erythropterus, in Korea induced by plerocercoid larvae of Ligula intestinalis as a result of host manipulation. The carcasses of fish with ligulid larvae were first found in the river-edge areas of Chilgok-bo in Nakdong-gang (River), Korea at early February 2016. This ecological phenomena also occurred in the adjacent areas of 3 dams of Nakdong-gang, i.e., Gangjeong-bo, Dalseong-bo, and Hapcheon-Changnyeong-bo. Total 1,173 fish carcasses were collected from the 4 regions. To examine the cause of death, we captured 10 wondering carp in the river-edge areas of Hapcheon-Changnyeong-bo with a landing net. They were 24.0-28.5 cm in length and 147-257 g in weight, and had 2-11 plerocercoid larvae in the abdominal cavity. Their digestive organs were slender and empty, and reproductive organs were not observed at all. The plerocercoid larvae occupied almost all spaces of the abdominal cavity under the air bladders. The proportion of larvae per fish was 14.6-32.1% of body weight. The larvae were ivory-white, 21.5-63.0 cm long, and 6.0-13.8 g in weight. We suggest that the preference for the river-edge in infected fish during winter is a modified behavioral response by host manipulation of the tapeworm larvae. The life cycle of this tapeworm seems to be successfully continued as the infected fish can be easily eaten by avian definitive hosts.

Histopathological observations on mice experimentally infected with plerocercoid / 中国人兽共患病学报

To observe the histopathological changes of mice experimentally infected with plerocercoid,mice were infected orally by plerocercoids that were collected from Rana nigromaculatus (5 strips/mouse),and were killed 2-10 weeks later to undergo the histopathological observation.Plerocercoids were found in the skin,muscle,liver,lung cavity of mice.There were diffuse congested spots and capsule formation ;the fat tissue showed severe degeneration and necrosis.In the fibrous tissues ,moderate proliferation of the enveloping adipose tissue was demonstrated.In addition,a large number of acute and chronic inflammatory cell infiltration and abscess formation could be found.It is evident that the plerocercoids parasitize mainly in the subcutaneous tissues and muscles of mice.and mice experimentally infected with plerocercoids show different degree of histopathological changes.

Seroprevalence of Tissue Invading Parasitic Infections Diagnosed by ELISA in Korea

Seroprevalence of the IgG antibodies for Clonorchis sinensis, Paragonimus westermani, Taenia solium metacestode (cysticercus), and Spirometra erinacei plerocercoid (sparganum) was measured using enzyme-linked immunosorbent assay (ELISA) in sera of patients in Korea from 1993 to 2006. A total of 74,448 specimens referred nationwide from 121 hospitals revealed an IgG positive rate of 7.6% for the 4 parasites. The IgG positive rate (18.7%) for the 4 parasites in 1993 decreased gradually to 6.6% in 2006. Individual positive rate decreased from 5.2% (1993) to 1.6% (2006) for C. sinensis, from 2.8% (1993) to 1.1% (2006) for P. westermani, from 8.3% (1993) to 2.2% (2006) for cysticercus, and from 2.6% (1993) to 1.6% (2006) for sparganum. The positive rate was highest (21.2%) in the group of patients who ranged in age from 50-59 yr old, and in the group that was referred from the Seoul area (55.9%). In conclusion, our results suggest that tissue invading parasitic infections should always be included in differential diagnosis for patients with eosinophilia associated lesions of the central nervous system, liver, and lungs in Korea.

Partial Purification and Characterization of a Cysteine Protease Inhibitor from the Plerocercoid of Spirometra erinacei

Helminthic cysteine proteases are well known to play critical roles in tissue invasion, nutrient uptake, and immune evasion of the parasites. In the same manner, the sparganum, the plerocercoid of Spirometra mansoni, is also known to secrete a large amount of cysteine proteases. However, cysteine protease inhibitors regulating the proteolytic activities of the cysteine protease are poorly illustrated. In this regard, we partially purified an endogenous cysteine protease inhibitor from spargana and characterized its biochemical properties. The cysteine protease inhibitor was purified by sequential chromatographies using Resource Q anion exchanger and Superdex 200 HR gel filtration from crude extracts of spargana. The molecular weight of the purified protein was estimated to be about 11 kD on SDS-PAGE. It was able to inhibit papain and 27 kDa cysteine protease of spargana with the ratio of 25.7% and 49.1%, respectively, while did not inhibit chymotrypsin. This finding suggests that the cysteine protease inhibitor of spargana may be involved in regulation of endogenous cysteine proteases of the parasite, rather than interact with cysteine proteases from their hosts.

Feminization and reduction of testicular weight in mouse sparganosis

After infection of male mice with the plerocercoids (spargana) of Spirometra mansoni, serum levels of estrogen and testicular weight were analyzed by enzyme-linked immunosorbent assay (ELISA) and weighing machine, respectively. The serum level of estrogen increased progressively in infected mice compared with normal controls, whereas the testicular weight of infected mice decreased significantly (P < 0.05). These results suggest that certain substances from spargana change the steroid hormone metabolisms in the host by unknown pathways, and chronic infection may contribute to change of the function of steroid hormone target organ, i.e., testis, in male mice.

A new method for concentration of proteins in the calcareous corpuscles separated from the spargana of Spirometra erinacei

Calcareous corpuscles are a characteristic structure found in larval and adult stage cestodes. These corpuscles are known to contain several protein components and to possess protein-binding activity. However, the proteins bound to calcareous corpuscles in situ have not been studied. The present study was undertaken to identify the proteins on calcareous corpuscles. Calcareous corpuscles were purified from the plerocercoids (= spargana) of Spirometra erinacei, and serially dissolved using 0.1 M sulfamic acid solution. Collected supernatants were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining. The results showed that only the fraction remaining after the 19th dissolved fraction contained proteins. A total of 20 protein molecules were detected in gel, with major bands at 56, 53, 46, 40, 35, 29, 28, 24.5, 21, 19, 16, 13, 10 and 8 kDa. In particular, the proteins corresponding to the 21 and 16 kDa bands were most abundant. Our results demonstrated for the first time the protein contents of the calcareous corpuscles of spargana. Further studies on the functions of these proteins are required.

Human Plerocercoidosis and Sparganosis:Ⅱ.A Historical Review on Pathology, Clinics, Epidemiology and Control / 中国寄生虫学与寄生虫病杂志

This article is the second part of the previous review and summarizes the research advances on pathol-ogy, clinical manifestation, diagnosis, treatment, epidemiology, and control of human plerocercoidosis and sparganosis.

Human Plerocercoidosis and Sparganosis :Ⅰ.A Historical Review on Aetiology / 中国寄生虫学与寄生虫病杂志

Plerocercoid should not be confused with Sparganum.The scolex of plerocercoid has a bothrium or bothrial slit but there is no true scolex in sparganum.Plerocercoid is a developmental stage of an animal tapeworm,Genus Spirometra.Sparganum is another generic name of a pseudophyllidean cestode.Plerocercoid causes benign plerocercoidosis and sparganum causes "malignant sparganosis".Plerocercoidosis is a parasitic zoonosis which can be food-borne,water-borne,contact-borne or mother-borne.During the past 20 years,there has been significant progress in studies of human plerocercoidosis and sparganosis,especially the former.Spirometra erinacei-europiea plerocercoidosis and sparganosis pro-lifera distributed mainly in East Asia.Spirometra mansonoides plerocercoidosis has been reported from the USA.Up to the present,approximately 1 400 cases of plerocercoidosis were reported from China,Japan,Korea,USA and Thailand,and at least 16 well-documented cases of human proliferating sparganosis were reported worldwide(in Japan,China,Thailand,USA,Paraguay,Venezuela,and the Philippines).The life cycle of Sparganum is unknown.For plerocercoid,human being acts as a dead-end hosts,copepod and frogs serve as intermediate hosts,and snakes and carnivorous animals are its paratenic hosts.This review summarizes the research progresss on aetiology and pathogenesis of human plerocercoidosis and sparganosis.The second part(in press) will be concentrated on their pathology,clinical manifesta-tions,diagnosis,treatment,epidemiology,control and prevention.