BACKGROUND: Tapeworms of the order Diphyllobothriidea are parasites of tetrapods and several species may infect man and cause neglected human disease called diphyllobothriosis. Identification of human-infecting diphyllobothriid cestodes is difficult because of their morphological uniformity, which concerns also their eggs in stool samples. METHODS: In the present study, we analysed by far the largest dataset of more than 2,000 eggs of 8 species of diphyllobothriid cestodes that may infect humans, including the most frequent human parasites Diphyllobothrium latum, D. nihonkaiense and Adenocephalus pacificus (syn. Diphyllobothrium pacificum). Size (length, width and length/width ratio) and the surface of the egg shell from naturally and experimentally infected hosts were studied using light and scanning electron microscopy. RESULTS: A high degree of intraspecific and host-related size variability has been detected, but combination of morphometrical and ultrastructural data made it possible to distinguish all of the studied species, including otherwise quite similar eggs of the 3 most common species infecting man, i.e. D. latum, D. nihonkaiense and D. dendriticum. The surface of all marine species is covered by numerous deep pits with species-specific density, whereas the surface of freshwater species is smooth or with isolated shallow hollows or wrinkles.

Institute of Parasitology Biology Centre of the Czech Academy of Sciences and Faculty of Science University of South Bohemia České Budějovice Czech Republic

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Ash LR, Orihel TC (2007) Atlas of Human Parasitology. Singapore: ASCP Press.

Kuchta R, Scholz T, Brabec J, Narduzzi-Wicht B (2015) Chapter 17. Diphyllobothrium, Diplogonoporus and Spirometra In: Xiao L, Ryan U, Feng F, editors. Biology of Foodborne Parasites Section III Important Foodborne Helminths: CRC Press; pp. 299–326.

Kuchta R, Brabec J, Kubáčková P, Scholz T (2013) Tapeworm Diphyllobothrium dendriticum (Cestoda)–Neglected or emerging human parasite? PLoS Negl Trop Dis 7: e2535 doi: 10.1371/journal.pntd.0002535 PubMed DOI PMC

Kuchta R, Serrano-Martinez ME, Scholz T (2015) Pacific broad tapeworm Adenocephalus pacificus as a causative agent of globally reemerging diphyllobothriosis. Emerg Infect Dis 21: 1697–1703. doi: 10.3201/ PubMed PMC

de Marval F, Gottstein B, Weber M, Wicht B (2013) Imported diphyllobothriasis in Switzerland: molecular methods to define a clinical case of Diphyllobothrium infection as Diphyllobothrium dendriticum. Eurosurveillance 18: 31–36. PubMed

Nicholson D (1928) Fish tapeworm, intestinal infection in man: The infestation of fish in Manitoba lake. Can Med Assoc J 19: 25–33. PubMed PMC

Bonsdorff Bv (1977) Diphyllobothriasis in man London: Academic Press.

Essex HE, Magath TB (1931) Comparison of the variability of ova of the broad fish tapeworm, Diphyllobothrium latum, from man and dogs: its bearing on the spread of infestation with this parasite. Am J Hyg 14: 698–704.

Vergeer T (1936) The eggs and the coracidia of Diphyllobothrium latum. Papers of the Michigan Academy of Sciences, Arts and Letters 21: 715–727.

Andersen KI, Halvorsen O (1978) Egg size and form as taxonomic criteria in Diphyllobothrium. Parasitology 76: 229–240. PubMed

Tsuboi T, Torii M, Hirai K (1993) Light and scanning electron microscopy of Diphyllobothrium pacificum expelled from a man. Jpn J Parasitol 42: 422–428.

Choi S, Cho J, Jung B-K, Kim D-G, Jeon S, et al. (2015) Diphyllobothrium nihonkaiense: wide egg size variation in 32 molecularly confirmed adult specimens from Korea. Parasitol Res 114: 2129–2134. doi: 10.1007/s00436-015-4401-7 PubMed DOI

Fraser PG (1960) The form of the larval hooks as a means of separating species of Diphyllobothrium. J Helminthol 34: 73–80.

Hilliard DK (1960) Studies on the helminth fauna of Alaska. XXXVIII. The taxonomic significance of eggs and coracidia of some diphyllobothriid cestodes. J Parasitol 46: 703–715. PubMed

Vik R (1964) The genus Diphyllobothrium. An example of the interdependence of systematics and experimental biology. Exp Parasitol 15: 361–380. PubMed

Yazaki S (1982) Studies on three dimentional features of embryonic hooks in some species of diphyllobothriids, with special reference to taxonomic significance. Jpn J Parasitol 31: 435–446. (In Japanese.)

Hernández-Orts JS, Scholz T, Brabec J, Kuzmina T, Kuchta R (2015) High morphological plasticity and global geographical distribution of the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum): Molecular and morphological survey. Acta Trop 149: 168–178. doi: 10.1016/j.actatropica.2015.05.017 PubMed DOI

Maltsev VN, Gavrilova NA (1994) Variation of morphological characters within different parts of the strobila in cestodan genus Diphyllobothrium (Cestoda, Diphyllobothriidae). Zool Zh 1994: 59–62. (In Russian.)

Kuchta R, Caira JN (2010) Three new species of Echinobothrium (Cestoda: Diphyllidea) from Indo-Pacific stingrays of the genus Pastinachus (Rajiformes: Dasyatidae). Folia Parasitol 57: 185–196. PubMed

Maejima J, Yazaki S, Fukumoto S (1983) Morphological comparison of eggs between marine species and freshwater species in diphyllobothriid cestodes. Jpn J Parasitol 32: 27–42. (In Japanese.)

Chai JY, Murrell KD, Lymbery AJ (2005) Fish-borne parasitic zoonoses: Status and issues. Int J Parasitol 35: 1233–1254. PubMed

Kuchta R, Esteban J-G, Brabec J, Scholz T (2014) Misidentification of Diphyllobothrium species related to global fish trade, Europe. Emerg Inf Dis 20: 1955–1957. PubMed PMC

Kuhlow F (1953) Über die Entwicklung und Anatomie von Diphyllobothrium dendriticum, Nitzsch 1824. Z Parasitenkd 16: 1–35. PubMed

Torres P, Torres J, Garrido O, Thibaut J (1989) Investigaciones sobre Pseudophyllidea (Carus, 1813) en el sur de Chile. X. Observaciones experimentales sobre la coexistencia de plerocercoides de Diphyllobothrium latum (L.) y Diphyllobothrium dendriticum (Nitszch) en salmónidos de la cuenca del río Valdivia. Arch Med Vet 21: 51–57.

Maejima J, Yazaki S, Fukumoto S (1991) Comparative studies on egg-sizes and -forms of various Diphyllobothrium species from man in Japan. Jpn J Parasitol 40: 170–176. (In Japanese.)

Magath T (1919) The eggs of Diphyllobothrium latum. J Am Med Assoc 73: 85–87.

Kim H-J, Eom KS, Seo M (2014) Three cases of Diphyllobothrium nihonkaiense infection in Korea. Kor J Parasitol 52: 673–676. PubMed PMC

Yazaki S, Fukumoto S, Maejima J, Miyahara M (1990) Comparative observations of Diphyllobothrium pacificum from a man and from fur seals. J Yonago Med Ass 41: 204–210. (In Japanese.)

Hilliard DK (1972) Studies on the helminth fauna of Alaska. LI. Observations on eggshell formation in some diphyllobothriid cestodes. Can J Zool 50: 585–592. PubMed

Yamane Y, Seki R, Okada N (1976) Comparative observation on surface topography of teguments and egg shells of diphyllobothriid cestodes by scanning electron microscopy. Yonago Acta Med 20: 55–65. PubMed

Wicht B, Yanagida T, Scholz T, Ito A, Jiménez JA, et al. (2010) Multiplex PCR for differential identification of broad tapeworms (Cestoda: Diphyllobothrium) infecting humans. J Clin Microbiol 48: 3111–3116. doi: 10.1128/JCM.00445-10 PubMed DOI PMC