Echinococcus Rudolphi, 1801

Sasaki, Mizuki, Anders, Jason Lee & Nakao, Minoru, 2021, Cestode fauna of murid and cricetid rodents in Hokkaido, Japan, with assignment of DNA barcodes, Species Diversity 26, pp. 255-272 : 266-268

Genus Echinococcus Rudolphi, 1801 10. Echinococcus multilocularis Leuckart, 1863

The lesions of alveolar hydatid containing numerous protoscoleces were found from the liver, lungs, and abdominal cavity of My. rufocanus in Asahikawa and Otofuke ( Fig. 9C ). The appearance of the lesions completely agreed with that of Echinococcus multilocularis ( Houin et al. 1982; Miller et al. 2016). Although the two isolates of E. multilocularis were obtained in this study, we did not perform any detailed analysis because the morphological feature and genetic uniformity of E. multilocularis have already been well examined in Hokkaido ( Yagi et al. 1986; Iwaki et al. 1993; Nakao et al. 2003; Okamoto et al. 2007).

This species is well known to cause human alveolar echinococcosis, which is one of the most important zoonoses in the Holarctic region. A small number of the human cases occur every year in Hokkaido ( Takahashi et al. 2005; National Institute of Infectious Diseases 2019; Kamiyama 2020). The red fox, Vulpes vulpes Linnaeus, 1758 , is the main definitive host of E. multilocularis ( Romig et al. 2017; Tsukada et al. 2000). It seems that E. multilocularis has been recently introduced into Hokkaido from the Kurile islands by migrant foxes on drift ice or the anthropogenic movement of foxes and rapidly spread throughout Hokkaido ( Yamashita 1956). A lower genetic divergence among the parasite population in Hokkaido supports this hypothesis ( Nakao et al. 2003; Okamoto et al. 2007). Red foxes are colonizing urban areas because they can adapt to the artificial environment ( Tsukada et al. 2000; Uraguchi et al. 2009). One of the present isolates was obtained from an urban park in Asahikawa.

Conclusion. Our collections and literature search revealed that the cestode fauna of murid and cricetid rodents in Japan consists of at least 30 species from 6 families ( Table 2) . Among them, 23 species occur in Hokkaido . The species composition is strongly affected by the nearby Eurasian continent . It is most likely that the diverse cestode fauna is caused by rodent migrations over land bridges between Hokkaido and Sakhalin and between Hokkaido and Honshu during the late Pleistocene . The recent anthropogenic introduction of host animals seems to be responsible for the distribution of T. crassiceps , Hyd. taeniaeformis , Hyd. kamiyai , and E. multilocularis . This report contains the first records of A. tenuicirrosa , P. kalelai , and T. crassiceps from Hokkaido. The former two species correspond to the first records in Japan . Several cestodes are still waiting to be further investigated and placed into suitable taxonomic positions by an integrated approach of molecular phylogeny, morphology, and ecology.

In this study, nuclear and mitochondrial DNA barcodes were generated for some cestodes from rodents in Hokkaido ( Table 1). The DNA barcoding system has a great potential to revise existing classification systems and to accelerate the discovery of cryptic species. In order to expand its potential, it is necessary to enhance DNA databases with reliable data from cestode taxonomists across the world. Moreover, it is most important to standardize DNA markers for the taxonomy of cestodes. In previous studies on rodent cestodes, various regions of nuclear and mitochondrial DNA were used as DNA markers for phylogenetic analyses ( Haukisalmi et al. 2004; Haukisalmi et al. 2010b; Makarikov et al. 2013). The use of the markers, however, lacks consistency. We especially recommend the primer set, JB3 and CO1-R trema ( Miura et al. 2005), because it enables the amplification of cox 1 sequences (approximately 800 bases in length) from most platyhelminths. The sequencing of mitochondrial cox 1 and nuclear 28S rDNA is a minimum requirement for the species and genus level identification of cestodes.

Figures

Fig. 9. Larvae of the family Taeniidae. A, The proliferated cysticerci of Taenia crassiceps in the subcutaneous tissue of Myodes rufocanus; B, the strobilocercus of Hydatigera taeniaeformis from the liver of Rattus norvegicus; C, the disseminated alveolar hydatid of Echinococcus multilocularis in peritoneal organs of My. rufocanus. Scale bars: 20mm.