Severe fever with the thrombocytopenia syndrome virus (SFTSV) causes fatal disease in humans, cats, and cheetahs. In this study, the information on seven dogs with SFTS was summarized. All dogs showed anorexia, high fever, leukopenia, and thrombocytopenia, two dogs showed vomiting and loose stool, and five dogs had tick parasites. All dogs also had a history of outdoor activity. The SFTSV gene was detected in all dogs. Remarkably, three dogs (43%) died. SFTSV was isolated from six dogs and the complete genomes were determined. A significant increase in anti-SFTSV-IgG antibodies was observed in two dogs after recovery, and anti-SFTSV-IgM antibodies were detected in four dogs in the acute phase. Using an ELISA cut-off value of 0.410 to discriminate between SFTSV-negative and positive dogs, the detection of anti-SFTSV-IgM antibodies was useful for the diagnosis of dogs with acute-phase SFTS. Four out of the ninety-eight SFTSV-negative dogs possessed high anti-SFTSV IgG antibody titers, indicating that some dogs can recover from SFTSV infection. In conclusion, SFTSV is lethal in some dogs, but many dogs recover from SFTSV infection.

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.

Rabies is a fatal encephalitic infectious disease caused by the rabies virus (RABV). RABV is highly neurotropic and replicates in neuronal cell lines in vitro. The RABV fixed strain, HEP-Flury, was produced via passaging in primary chicken embryonic fibroblast cells. HEP-Flury showed rapid adaptation when propagated in mouse neuroblastoma (MNA) cells. In this study, we compared the growth of our previously constructed recombinant HEP (rHEP) strain—based on the sequence of the HEP (HEP-Flury) strain—with that of the original HEP strain. The original HEP strain exhibited higher titer than rHEP and a single substitution at position 80 in the matrix (M) protein M(D80N) after incubation in MNA cells, which was absent in rHEP. In vivo, intracerebral inoculation of the rHEP-M(D80N) strain with this substitution resulted in enhanced viral growth in the mouse brain and a significant loss of body weight in the adult mice. The number of viral antigen-positive cells in the brains of adult mice inoculated with the rHEP-M(D80N) strain was significantly higher than that with the rHEP strain at 5 days post-inoculation. Our findings demonstrate that a single amino acid substitution in the M protein M(D80N) is associated with neurovirulence in mice owing to adaptation to mouse neuronal cells.

Hepatitis E virus (HEV) is a zoonotic pathogen with multiple hosts, posing significant public health risks, especially in regions like Japan where game meat consumption is prevalent. This study investigated HEV infection and viral shedding in wild boars, sika deer, and Japanese serows across Japan. A total of 1896 serum samples were tested for anti-HEV antibodies, 1034 for HEV RNA, and 473 fecal samples for viral shedding. Anti-HEV antibodies were detected in wild boars from all seven prefectures studied, while HEV RNA was detected in wild boars from Fukuoka, Oita, and Miyazaki in southern Japan, as well as Yamaguchi prefecture. Genetic analysis revealed subtypes 3b, 4a, and 4g, with 3b being the most prevalent. Subtype 3b exhibited distinct geographical clustering, whereas 4g persisted exclusively in Yamaguchi for over 12 years. Infectious HEV particles were confirmed in wild boar feces, highlighting the risk of environmental contamination and zoonotic transmission. Sika deer showed no evidence of HEV infection, and only one Japanese serow tested positive for antibodies without detectable RNA. These findings underscore the importance of ongoing surveillance to assess the zoonotic risks from game meat consumption and prevention of HEV transmission to humans.