Tapeworms of the genus Spirometra are pseudophyllidean cestodes endemic in Korea. At present, it is unclear which Spirometra species are responsible for causing human infections, and little information is available on the epidemiological profiles of Spirometra species infecting humans in Korea. Between 1979 and 2009, a total of 50 spargana from human patients and 2 adult specimens obtained from experimentally infected carnivorous animals were analyzed according to genetic and taxonomic criteria and classified as Spirometra erinaceieuropaei or Spirometra decipiens depending on the morphology. Morphologically, S. erinaceieuropaei and S. decipiens are different in that the spirally coiled uterus in S. erinaceieuropaei has 5-7 complete coils, while in S. decipiens it has only 4.5 coils. In addition, there is a 9.3% (146/1,566) sequence different between S. erinaceieuropaei and S. decipiens in the cox1 gene. Partial cox1 sequences (390 bp) from 35 Korean isolates showed 99.4% (388/390) similarity with the reference sequence of S. erinaceieuropaei from Korea (G1724; GenBank KJ599680) and an additional 15 Korean isolates revealed 99.2% (387/390) similarity with the reference sequences of S. decipiens from Korea (G1657; GenBank KJ599679). Based on morphologic and molecular databases, the estimated population ratio of S. erinaceieuropaei to S. decipiens was 35: 15. Our results indicate that both S. erinaceieuropaei and S. decipiens found in Korea infect humans, with S. erinaceieuropaei being 2 times more prevalent than S. decipiens. This study is the first to report human sparganosis caused by S. decipiens in humans in Korea.

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The present study was performed to compare the mitochondrial genomes between 2 Spirometra tapeworms, Spirometra erinaceieuropaei and Spirometra decipiens (Cestoidea: Diphyllobothriidae), which larval stages are important etiological agents of sparganosis in humans. For each species, the full mitochondrial genome was amplified in 8 overlapping fragments using total genomic DNA purified from a single worm as the template. The mitochondrial genomes were 13,643 bp (S. erinaceieuropaei) and 13,641 bp (S. decipiens) in length and contained 36 genes; 12 protein-coding genes, 2 ribosomal RNA (rRNA, small and large subunits), and 22 transfer RNAs (tRNAs). The 12 protein-coding genes constituted 10,083 bp (S. erinaceieuropaei) and 10,086 bp (S. decipiens) of their respective mitochondrial genomes. The tRNA genes, ranging in length from 56 to 70 bp, were identified based on putative secondary structures such as the typical cloverleaf shape. A total of 23 intergenic sequences, varying from 1 to 204 bp in size, were interspersed in S. erinaceieuropaei (total, 504 bp) and S. decipiens (total, 496 bp) mtDNA. The 12 protein-coding genes of S. erinaceieuropaei and S. decipiens differed by 12.4%, whereas the overall difference in mtDNA sequence between S. erinaceieuropaei and S. decipiens was 12.9%. Thus, from the standpoint of the mitochondrial genome, S. decipiens represents a valid species that can be distinguished from S. erinaceieuropaei.

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).

Mitochondrial genomes have been extensively studied for phylogenetic purposes and to investigate intra- and interspecific genetic variations. In recent years, numerous groups have undertaken sequencing of platyhelminth mitochondrial genomes. Haplorchis taichui (family Heterophyidae) is a trematode that infects humans and animals mainly in Asia, including the Mekong River basin. We sequenced and determined the organization of the complete mitochondrial genome of H. taichui. The mitochondrial genome is 15,130 bp long, containing 12 protein-coding genes, 2 ribosomal RNAs (rRNAs, a small and a large subunit), and 22 transfer RNAs (tRNAs). Like other trematodes, it does not encode the atp8 gene. All genes are transcribed from the same strand. The ATG initiation codon is used for 9 protein-coding genes, and GTG for the remaining 3 (nad1, nad4, and nad5). The mitochondrial genome of H. taichui has a single long non-coding region between trnE and trnG. H. taichui has evolved as being more closely related to Opisthorchiidae than other trematode groups with maximal support in the phylogenetic analysis. Our results could provide a resource for the comparative mitochondrial genome analysis of trematodes, and may yield genetic markers for molecular epidemiological investigations into intestinal flukes.

In the present study, we identified a Spirometra species of Myanmar origin (plerocercoid) by molecular analysis using mitochondrial cox1 and nad1 genes, as well as by morphological observations of an adult tapeworm. Spargana specimens were collected from a paddy-field in Taik Kyi Township Tarkwa Village, Yangon, Myanmar in December 2017. A total of 5 spargana were obtained from 20 frogs Hoplobatrachus rugulosus; syn: Rana rugulosa (Wiegmann, 1834) or R. tigrina (Steindachner, 1867). The plerocercoids were used for experimental infection of a dog. After 4 weeks of infection, an adult tapeworm was recovered from the intestine of the dog. Morphologically, the distinct features of Spirometra sp. (Myanmar origin) relative to S. erinaceieuropaei and S. decipiens include a uterine morphology comprising posterior uterine coils that larger than the terminal uterine ball and coiling of the uteri diagonally (swirling) rather than spirally. The cox1 sequences (1,566 bp) of the Myanmar-origin Spirometra species showed 97.9% similarity to a reference sequence of S. decipiens (GenBank no. KJ599679) and 90.5% similarity to a reference sequence of S. erinaceieuropaei (GenBank no. KJ599680). Phylogenetic tree topologies were identical and presented high confidence level of values for the 3 major branches of the 3 Spirometra species in cox1 and nad1 genes. These results indicated that Myanmar-origin Spirometra species coincided with those of S. ranarum and may be considered as a valid species.

Three echinostome species, i.e., Patagifer bilobus, Petasiger neocomense, and Saakotrema metatestis, are newly recorded in the trematode fauna of the Republic of Korea. They were recovered from 3 species of migratory birds (Platalea minor, Podiceps cristatus, and Egretta garzetta), which were donated by the Wildlife Center of Chungbuk (WCC) and the Conservation Genome Resource Bank for Korean Wildlife (CGRB). Only 1 P. bilobus specimen was recovered from the intestine of a black-faced spoonbill (P. minor), and characterized by the bilobed head crown with a deep dorsal incision and 54 collar spines. Twenty P. neocomense were recovered from the intestine of a great crested grebe (P. cristatus), and they had a well-developed head crown with 19 spines and 2 testes obliquely located at the posterior middle of the body. Total 70 S. metatestis were collected from the bursa of Fabricius of 1 little egret (E. garzetta). It is characterized by stout tegumental spines covered in the entire leaf-shaped body, posterior extension of the uterus, presence of the uroproct and a well-developed head crown with 12 pairs of collar spines on each side. By the present study, these 3 echinostome species are newly added to the trematode fauna in Korea.

Myiasis is a relatively common infection of animals kept as pets, although only 1 case of canine myiasis has been described so far in the Republic of Korea. In the present study, we report an additional case of canine wound myiasis with identification of its causative agent, Lucilia sericata. An 8-year-old male Siberian husky dog was referred with anorexia, vomiting, and diarrhea to the Chungbuk National University Veterinary Medical Center, Cheongju-si (city), Chungcheongbuk-do (province), Korea in July 2013. Physical examination indicated the patient had a deep wound filled with a maggot swarm as a left gluteal lesion. A total of 216 maggots were removed by forceps, and the wounded area was sponged with gauzes and disinfected with 70% alcohol and a povidone-iodine solution. After daily care and suturing the wound, the patient was discharged at day 19 after admission. Recovered worms possessed morphological characteristics similar to those of L. sericata, namely, a sub-cylindrical body with 6–8 lobed anterior spiracles, round shaped with a button surrounded by a peritremal ring with no gaps, and similar distances between dorsal, median, and outer papillae of the 12th segment. Additionally, cox1 partial sequences (528 bp) obtained in the present study showed 100% identity with those of L. sericata (GenBank no. KT272854.1). L. sericata is indicated as a pathogen of myiasis infection not only in humans, but also in animals kept as pets in Korea.