The perinatal transmission of bovine leukaemia virus (BLV) plays a critical role in the spread and persistence of BLV infection in cattle herds. The purpose of this study was to examine the frequency of perinatal infections in an area in Japan and investigate some risk factors associated with infection. Altogether, 129 calves born to BLV-infected cows in a herd in Japan were tested for infection immediately after birth and again at one month of age using nested PCR. Twenty-four calves (18.6 per cent) were infected with BLV, of which 14 (10.8 per cent) and 10 (7.7 per cent) calves were infected via the transplacental and the birth canal routes, respectively. Maternal viral loads, breed, the presence or absence of assistance during parturition and the number of births per dam were evaluated to investigate risk factors associated with infection. Maternal viral load was significantly correlated with the frequency of perinatal infection, and more than 40 per cent of newborn calves born to dams with high viral loads were infected with BLV. The results of this study could contribute towards developing effective eradication programmes by providing necessary data for replacement of breeding cow in the field.

S evere fever with thrombocytopenia syndrome (SFTS) is caused by the species Dabie bandavirus (family Phenuiviridae, genus Bandavirus), generally called severe fever with thrombocytopenia syndrome virus (SFTSV) (1,2). Cases of SFTS were identified in patients in China during 2009 (3) and subsequently in Japan and South Korea (2,4). Clinical signs include high fever, fatigue, gastrointestinal symptoms, neurologic symptoms, thrombocytopenia, leukocytopenia, and multiorgan failure (5). SFTS is potentially fatal, and mortality rates have reached 27% in Japan (6). Although the clinical information regarding SFTS in most animals is unclear, cats show fatal symptoms similar to those in humans (7). Enzootic SFTSV transmission is primarily tickborne; tick bites can also spread the virus to humans (8) and animals (9). Human-to-human transmission occurs rarely through contact with infected blood, body fluids, or mucus (10) and possibly by aerosols (11). In this study, we provide evidence for the direct cat-to-human transmission of the virus, leading to a nosocomial outbreak of SFTSV infection. The Study Confirmatory testing of veterinary personnel samples was performed at the Laboratory of Microbiology, Miyazaki Prefecture Institute for the Public Health and Environment, Miyazaki, Japan. Cat sample analysis was performed at the Center for Animal Disease Control, University of Miyazaki. A 1-year-old male domestic cat was hospitalized on August 15, 2018, with jaundice, poor appetite, vomiting, and a rectal temperature of 40.4°C. Hematologic examination showed leukocytopenia (1,080 cells/µL, reference range 4-30 × 10 3 cells/µL), thrombocytopenia (19,000 cells/µL, reference range 9-90 × 10 4 cells/µL), and an increased level of total bilirubin (3.1 mg/dL, reference range 0-0.5 mg/dL) (12) (Table). The cat died 3 days after hospitalization. Serum samples, saliva samples, and anal swab specimens (sampled on the first day of hospitalization) were sent to the Center for Animal Disease Control, University of Miyazaki, for molecular test targeting the small segment RNA of SFTSV by reverse transcription PCR (RT-PCR) and real-time RT-PCR (3). The amounts of SFTSV RNA were quantified as RNA copies per milliliter of serum. We detected a viral load of 1.5 × 10 11 copies/mL (Table). During hospitalization, the cat came into contact with a veterinarian (44-year-old woman) and a veterinary technician (20-year-old woman). During contact, both veterinary personnel wore protective clothing (gloves and surgical masks), but their eyes remained unprotected; they were not bitten or scratched by the cat. In addition, neither was bitten by ticks. After the death of the cat, symptoms consistent with SFTS developed in both veterinary personnel (Figure 1). Ten days after the death of the cat, on August 27, the veterinarian (patient 1) was hospitalized with a high fever (body temperature 39.2°C),

Cattle are major reservoirs of the provisionally named influenza D virus, which is potentially involved in the bovine respiratory disease complex. Here, we conducted a serological survey for the influenza D virus in Japan, using archived bovine serum samples collected during 2010–2016 from several herds of apparently healthy cattle in various regions of the country. We found sero-positive cattle across all years and in all the prefectural regions tested, with a total positivity rate of 30.5%, although the positivity rates varied among regions (13.5–50.0%). There was no significant difference in positivity rates for Holstein and Japanese Black cattle. Positivity rates tended to increase with cattle age. The herds were clearly divided into two groups: those with a high positive rate and those with a low (or no) positive rate, indicating that horizontal transmission of the virus occurs readily within a herd. These data demonstrate that bovine influenza D viruses have been in circulation for at least 5 years countrywide, emphasizing its ubiquitous distribution in the cattle population of Japan.

The bovine MHC (BoLA) class II DRB3 alleles are associated with polyclonal expansion of lymphocytes caused by bovine leukemia virus (BLV) infection in cattle. To examine whether the DRB3*0902 allele, one of the resistance-associated alleles, is associated with the proviral load, we measured BLV proviral load of BLV-infected cattle and clarified their DRB3 alleles. Fifty-seven animals with DRB3*0902 were identified out of 835 BLV-infected cattle and had significantly lower proviral load (P<0.000001) compared with the rest of the infected animals, in both Japanese Black and Holstein cattle. This result strongly indicates that the BoLA class II DRA/DRB3*0902 molecule plays an important immunological role in suppressing viral replication, resulting in resistance to the disease progression.

Horizontal transmission is recognized as a major infection route for bovine leukemia virus (BLV), and cattle with high viral loads are considered to be a major infectious source in a herd. However, a correlation between viral loads and the risk of infection has been insufficient to use as a foundation for BLV control strategies. In this report, we examined the epidemiology of BLV infection and the infectious source in a local area. In 2013–2014, BLV infection was investigated in 1,823 cattle from 117 farms in two adjacent districts, Miyazaki, Japan. Seropositive samples for BLV were detected with 88 cattle and in 14 farms. Phylogenetic analysis revealed that 94% of the isolates clustered into genotype I and the remaining isolate into genotype III. Among genotype I, genetically distinct strains were spread at each farm, and cattle infected with less than 3 copies/100 cells did not transmit BLV to other cattle for more than thirty months. This is the first report of concrete data of viral load in relation to viral horizontal transmission under the field condition. The data facilitate farmers and veterinarians understanding the status of BLV infected cattle. This research contributes to BLV infection control and the development of effective BLV eradication programs.