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Migratory birds carry ticks harboring various pathogens, including the zoonotic Yezo virus. In Hokkaido, Japan, we collected ticks from migratory birds during 2020-2021. Eight of 385 pools, comprising 2,534 ticks, tested positive for Yezo virus RNA, suggesting Yezo virus might be spread through the flyways of migratory birds.

The persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among wildlife populations poses a potential risk for the emergence of novel variants. Therefore, monitoring SARS-CoV-2 infections in animals is crucial. As urban rodents live in close proximity to human habitats, there is a concern that they may be a potential source of zoonoses. To examine the prevalence of SARS-CoV-2 in rodent populations, we analyzed 128 serum samples and 129 oral swabs collected from 128 brown rats (Rattus norvegicus) and two black rats (Rattus rattus) captured for pest control purposes in Tokyo, Japan, between May and December 2023. A virus-neutralizing test using the omicron variant revealed no evidence of SARS-CoV-2 infection. Real-time reverse transcription- PCR of oral swabs did not detect any SARS-CoV-2 RNA-positive rats. These results indicate a low probability of SARS-CoV-2 circulation among rat populations in Tokyo.

Some lyssaviruses, including the rabies virus (RABV), cause lethal neurological symptoms in humans. However, the efficacy of commercial vaccines has only been evaluated against RABV. To assess cross-reactivity among lyssaviruses, including RABV, sera from rabbits inoculated with human and animal RABV vaccines and polyclonal antibodies from rabbits immunized with expression plasmids of the glycoproteins of all 18 lyssaviruses were prepared, and cross-reactivity was evaluated via virus-neutralization tests using Duvenhage lyssavirus (DUVV), European bat lyssavirus-1 (EBLV-1), Mokola lyssavirus (MOKV), Lagos bat lyssavirus (LBV), and RABV. The sera from rabbits inoculated with RABV vaccines showed cross-reactivity with EBLV-1 and DUVV, both belonging to phylogroup I. However, reactivity with MOKV and LBV in phylogroup II was notably limited or below the detection level. Next, we compared the cross-reactivity of the polyclonal antibodies against all lyssavirus glycoproteins. Polyclonal antibodies had high virus-neutralization titers against the same phylogroup but not different phylogroups. Our findings indicate that a new vaccine should be developed for pre- and post-exposure prophylaxis against lyssaviral infections.

During their blood-feeding process, ticks are known to transmit various viruses to vertebrates, including humans. Recent viral metagenomic analyses using next-generation sequencing (NGS) have revealed that blood-feeding arthropods like ticks harbor a large diversity of viruses. However, many of these viruses have not been isolated or cultured, and their basic characteristics remain unknown. This study aimed to present the identification of a difficult-to-culture virus in ticks using NGS and to understand its epidemic dynamics using molecular biology techniques. During routine tick-borne virus surveillance in Japan, an unknown flaviviral sequence was detected via virome analysis of host-questing ticks. Similar viral sequences have been detected in the sera of sika deer and wild boars in Japan, and this virus was tentatively named the Saruyama virus (SAYAV). Because SAYAV did not propagate in any cultured cells tested, single-round infectious virus particles (SRIP) were generated based on its structural protein gene sequence utilizing a yellow fever virus-based replicon system to understand its nationwide endemic status. Seroepidemiological studies using SRIP as antigens have demonstrated the presence of neutralizing antibodies against SAYAV in sika deer and wild boar captured at several locations in Japan, suggesting that SAYAV is endemic throughout Japan. Phylogenetic analyses have revealed that SAYAV forms a sister clade with the Orthoflavivirus genus, which includes important mosquito- and tick-borne pathogenic viruses. This shows that SAYAV evolved into a lineage independent of the known orthoflaviviruses. This study demonstrates a unique approach for understanding the epidemiology of uncultured viruses by combining viral metagenomics and pseudoinfectious viral particles., Competing Interests: Competing interests statement:The authors declare no competing interest.

BACKGROUND: Vaccination against mpox (formerly known as monkeypox), an infectious disease caused by the monkeypox virus (MPXV), is needed to prevent outbreaks and consequent public health concerns. The LC16m8 vaccine, a dried cell-cultured proliferative live attenuated vaccinia virus–based vaccine, was approved in Japan against smallpox and mpox. However, its immunogenicity and efficacy against MPXV have not been fully assessed. We assessed the safety and immunogenicity of LC16m8 against MPXV in healthy adults. METHODS: We conducted a single-arm study that included 50 participants who were followed up for 168 days postvaccination. The primary end point was the neutralizing antibody seroconversion rate against MPXVs, including the Zr599 and Liberia strains, on day 28. The secondary end points included the vaccine “take” (major cutaneous reaction) rate, neutralizing titer kinetics against MPXV and vaccinia virus (LC16m8) strains, and safety outcomes. RESULTS: Seroconversion rates on day 28 were 72% (36 of 50), 70% (35 of 50), and 88% (44 of 50) against the Zr599 strain, the Liberia strain, and LC16m8, respectively. On day 168, seroconversion rates decreased to 30% (15 of 50) against the Zr599 and Liberia strains and to 76% (38 of 50) against LC16m8. The vaccine “take” (broad definition) rate on day 14 was 94% (46 of 49). Adverse events (AEs), including common solicited cutaneous reactions, occurred in 98% (45 of 48) of participants; grade 3 severity AEs occurred in 16% (8 of 50). No deaths, serious AEs, or mpox onset incidences were observed up to day 168. CONCLUSIONS: The LC16m8 vaccine generated neutralizing antibody responses against MPXV in healthy adults. No serious safety concerns occurred with LC16m8 use. (Funded by the Ministry of Health, Labour and Welfare of Japan; Japan Registry of Clinical Trials number, jRCTs031220171.)

Rabies is a fatal zoonotic, neurological disease caused by rabies lyssavirus (RABV) and other lyssaviruses. In this study, we established novel serological neutralizing tests (NT) based on vesicular stomatitis virus pseudotypes possessing all 18 known lyssavirus glycoproteins. Applying this system to comparative NT against rabbit sera immunized with current RABV vaccines, we showed that the current RABV vaccines fail to elicit sufficient neutralizing antibodies against lyssaviruses other than to those in phylogroup I. Furthermore, comparative NT against rabbit antisera for 18 lyssavirus glycoproteins showed glycoproteins of some lyssaviruses elicited neutralizing antibodies against a broad range of lyssaviruses. This novel testing system will be useful to comprehensively detect antibodies against lyssaviruses and evaluate their cross-reactivities for developing a future broad-protective vaccine.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne zoonotic disease caused by the SFTS virus (SFTSV). In Thailand, three human cases of SFTS were reported in 2019 and 2020, but there was no report of SFTSV infection in animals. Our study revealed that at least 16.6% of dogs in Thailand were seropositive for SFTSV infection, and the SFTSV-positive dogs were found in several districts in Thailand. Additionally, more than 70% of the serum samples collected at one shelter possessed virus-neutralization antibodies against SFTSV and the near-complete genome sequences of the SFTSV were determined from one dog in the shelter. The dog SFTSV was genetically close to those from Thailand and Chinese patients and belonged to genotype J3. These results indicated that SFTSV has already spread among animals in Thailand.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among pets owned by coronavirus disease 2019 (COVID-19) patients has been reported around the world. However, how often the animals are exposed to SARS-CoV-2 by their owners is still unclear. We have collected swab samples from COVID-19 patients' pets and performed real-time RT-PCR to detect the viral genome. In total, 8 of 53 dogs (15.1%) and 5 of 34 cats (14.7%) tested positive for the SARS-CoV-2 N gene. The result of a virus neutralization (VN) test also showed VN antibodies in four cats and six dogs. Our results indicate that the virus often passed from infected owners to their pets, which then excreted the virus despite having no or mild clinical signs.

In Japan, the first patient with severe fever with thrombocytopenia syndrome was reported in Yamaguchi in 2012. To understand the severe fever with thrombocytopenia syndrome virus (SFTSV) infection in this region, a retrospective surveillance in sika deer and wild boars in Yamaguchi was conducted using a virus-neutralizing (VN) test. The result revealed that 510 of the 789 sika deer and 199 of the 517 wild boars were positive for anti-SFTSV antibodies. Interestingly, seroprevalence in sika deer increased significantly from 2010-2013 to 2015-2020. The SFTSV gene was detected in one of the 229 serum samples collected from sika deer, but not from wild boars. In conclusion, SFTSV had spread among wild animals before 2012 and expanded gradually around 2013-2015 in Yamaguchi.

Getah virus (GETV) is a mosquito-borne RNA virus belonging to the family Togaviridae, genus Alphavirus. GETV infection causes diarrhoea and death in piglets, and reproductive failure and abortion in sows. This study conducted a serological survey of GETV infection among domestic pig populations in Thailand. ELISA was used to analyse 1,188 pig serum samples collected from 11 provinces of Thailand during 2017-2018, with 23.1% of the samples being positive for anti-GETV antibodies. The positive ratio of anti-GETV antibodies was significantly higher in nursery (67.9%) and older stages (84.5%) of pigs than in finishing stage (14.2%). Furthermore, we successfully isolated GETV from one pig serum, designated as GETV strain GETV/SW/Thailand/2017, and determined the complete genome sequence (11,689 nt). Phylogenetic analysis demonstrated that our isolate was different from the recent GETV group spreading among pig populations in East Asia and formed a cluster with two GETV strains, namely YN12031 (China, 2015) and LEIV16275Mar (Far-East Russia, 2007). We concluded that two different GETV groups are currently spreading among pig populations in Asian countries., (© 2021 Wiley-VCH GmbH.)