Effects of introduced sika deer (Cervus nippon) and population control activity on the distribution of Haemaphysalis ticks in an island environment

Characterization and arbovirus susceptibility of cultured CERNI cells derived from sika deer (Cervus nippon)

Cervus nippon (sika deer) are widely distributed throughout eastern Asia. Deer possess a variety of antibodies against several zoonotic pathogens, indicating that they act as reservoir of zoonoses. In this study, we reported the characterization of cultured cells derived from sika deer and evaluated their susceptibility to arthropod-borne viruses to clarify their usefulness in virological studies. Cells derived from testicular tissue in Dulbecco's modified eagle medium with 16% fetal bovine serum started growing as primary cultured cells. The diploid cells consisted of 68 chromosomes, consistent with those of Japanese sika deer previously reported. The phylogenetic analysis showed the cells formed a robust clade with Japanese population of C. nippon, indicating that the cultured cells established in this study were originated from the Japanese sika deer. The cells immortalized by the simian virus 40 T-antigen were predominantly spindle-shaped cells exhibiting adhesive properties, and cultivated at 37°C and 5% CO2, which are common culture conditions for many mammalian cell lines. Western blotting analysis indicated that the cultured cells were multiple types of cells that coexist, including at least epithelial, fibroblast, and also Leydig cells. We confirmed that the cells have susceptibility to several arboviruses distributed in Japan: Getah virus, Japanese encephalitis virus, Oz virus, and severe fever with thrombocytopenia syndrome virus, but not to Tarumiz tick virus. From these results, the cells contribute to clarify the role of sika deer as a reservoir of zoonoses in nature and deer-associated experimental research at the cellular and molecular levels.

First Detection of the Jingmen Tick Virus in Amblyomma testudinarium Ticks from the Kanto Region, Japan

In 2010, Jingmen tick virus (JMTV) was discovered in ticks in China and has been shown to be distributed in several regions worldwide. Recently, cases of JMTV infection in humans have been reported in China and Kosovo, and have attracted much attention as an emerging tick-borne disease. In this study, we detected the JMTV genome in Amblyomma testudinarium ticks collected in Kanagawa Prefecture, Japan, during tick-borne virus surveillance conducted in the Kanto Region. Phylogenetic analysis revealed that the new JMTV strain was closely related to previous strains detected in Japan. This suggests that JMTV may have been maintained during an independent natural transmission cycle in Japan. In addition, unlike other countries and regions, all JMTV strains in Japan were detected only in A. testudinarium ticks, suggesting that this tick species is the primary JMTV vector in Japan. This is the first report of JMTV in the Kanto Region. Further studies are required to elucidate the potential risk of infection with this tick-borne virus in Japan. In particular, the prevalence of JMTV in wild animals should be examined to clarify its geographical distribution, host range, and transmission cycle.

Morphological and Molecular Identification of Hard Ticks in Hainan Island, China

Ticks are small, blood-sucking arachnids, known vectors of various diseases, and found throughout the world. They are distributed basically in almost all regions of China. At present, there is not much information regarding tick species on Hainan Island. They were subjected to morphological identification and imaging on an individual basis. Molecular phylogenetic analyses, based on cox1 and 16S rRNA genes, were utilized to identify the species and determine their approximate phylogenetic origin and genetic diversity. The genomic DNA of tick species was extracted, and cytochrome oxidase subunit 1 (cox1) and 16S ribosomal RNA (rRNA) genes were amplified and sequenced. The identification of five tick species, namely Rhipicephalus microplus, Rhipicephalus sanguineus, Rhipicephalus haemaphysaloides, Haemaphysalis cornigera and Haemaphysalis mageshimaensis, was carried out by morphological analysis. When employing the cox1 and 16S rRNA phylogenetic tree, all isolates of R. microplus from Hainan Island were classified as clade A and B, respectively. R. sanguineus was recognized as a member of the tropical lineage by phylogenetic analysis on the cox1 and 16S rRNA genes. Three phylogenetic groups of R. haemaphysaloides were recognized and found to be related closely to strains from China. H. cornigera and H. mageshimaensis formed one phylogenetic group, presumably from tick strains prevalent in Japan and China. The haplotype network analysis indicated that R. microplus is classed into 26 and 6 haplotypes, which correspond to cox1 and 16S rRNA gene assemblages, respectively. In addition, four cox1 haplotypes were detected in R. sanguineus. This is the first evidence that suggests genetic diversity, host range and geographical distribution of hard ticks in Hainan Island, China.

Ecological traps and boosters of ixodid ticks: The differing ecological roles of two sympatric introduced mammals

The raccoon (Procyon lotor) and masked palm civet (Paguma larvata) are introduced species in Japan and have become abundant in human-inhabited environments. We surveyed tick infestations and tick ingestion by introduced raccoons and masked palm civets captured in Hayama, Kanagawa Prefecture, Japan between November 2018 and January 2020. We collected ticks from the body surface of animals and tick capitula from the gastrointestinal contents. We collected 18,357 ticks identified as Haemaphysalis flava, Haemaphysalis megaspinosa, Haemaphysalis longicornis, Ixodes ovatus, Ixodes tanuki, and Amblyomma testudinarium from 58 of 60 raccoons and 152 ticks, identified as H. flava and I. tanuki, from 16 of 41 masked palm civets. Furthermore, we obtained 16 capitula from 12 % of raccoons and 106 capitula from 63 % of masked palm civets. Raccoons harbored a greater number of ticks (all stages of H. flava and adult I. tanuki) compared with masked palmed civets, whereas the latter species ingested a greater number of nymphal and larval ticks. The results of this study extend our understanding of the ecological roles of two introduced wildlife species. The raccoon may act as an ecological booster, thereby increasing the success rate of bloodmeals and reproduction in ticks. In contrast, the masked palm civet may act as an ecological trap by effectively grooming to remove ticks and prevent bloodmeals.