Jianbo Zhu

The taxonomic species Palyam virus (PALV) comprises a group of widely distributed, Culicoides-borne arboviruses linked to bovine reproductive disorders, yet its genetic diversity and seroprevalence in China have not been fully characterized. To address this gap, we obtained 29 PALV isolates from sentinel cattle in southern China, performed whole-genome sequencing on 15 representative strains, and conducted a nationwide serosurvey of 4660 cattle using a newly developed c-ELISA. These genomic data were integrated with global datasets for comprehensive phylogenetic and phylogeographic analyses. By establishing a global VP2-based framework, the Chinese PALV isolates were assigned to the Chuzan, Bunyip Creek, and D’Aguilar genogroups. In the global context, Chinese PALV strains exhibited the closest genetic affinity with strains from Japan, while phylogeographic reconstruction suggests at least two independent introductions from Japan during the 1980s and 1990s. Our survey revealed a high overall seroprevalence of 46.5% (95% CI: 44.7–47.5%) in cattle, demonstrating a pronounced latitudinal gradient with a sharp ecological threshold at 32.5° N. The virus is hyperendemic in humid southern China, with seroprevalence ranging from 33.0% to 88.8%, but attenuated in northern regions with seroprevalence less than 8.0%. These findings redefine PALV as a widespread “silent threat” in the East Asian arbovirus ecosystem, highlighting the need for coordinated transboundary surveillance.

Yunnan Province is an area in China with a major prevalence of biting arthropods (including mosquitos, ticks, and Culicoides ) and arboviruses including dengue virus (DENV), bluetongue virus (BTV), and epizootic hemorrhagic disease virus (EHDV). Therefore, attempts to isolate and detect arboviruses are frequently conducted in Yunnan during the past decades. In this study, a total of three viral strains/isolates (LF6‐4, LF3‐1, and LF6C2) previously isolated from cattle, goat, and Culicoides in Lufeng County, Yunnan Province, between 2022 and 2023 were used for whole‐genome sequencing, phylogenetic analysis, and electron microscopic analysis. As a result, these viruses were completely sequenced. Strain LF6‐4 isolated from cattle was identified as a putative Serotype 1 Yunnan orbivirus (YUOV). Strain LF3‐1 isolated from goats was identified as Guangxi orbivirus (GXOV), and it is the first GXOV strain isolated from this animal. Isolate LF6C2 represented the first totivirus strain isolated from Culicoides . The viral particles of all three isolates collected from the infected C6/36 cells were all icosahedral particles with a diameter of approximately 45 nm. However, MDBK cells yielded YUOV and GXOV particles with diameters of approximately 75 nm. This difference may be caused by different viral proliferation/package modes in the different types of host cells.

Epizootic hemorrhagic disease (EHD) is an infectious viral disease caused by epizootic hemorrhagic disease virus (EHDV) and EHDV frequently circulates in wild and domestic ruminants. Sporadic outbreaks of EHD have caused thousands of deaths and stillbirths on cattle farms. However, not much is known about the circulating status of EHDV in Guangdong, southern China. To estimate the seroprevalence of EHDV in Guangdong province, 2886 cattle serum samples were collected from 2013 to 2017 and tested for antibodies against EHDV using a competitive ELISA. The overall seroprevalence of EHDV reached 57.87% and was highest in autumn (75.34%). A subset of positive samples were serotyped by a serum neutralization test, showing that EHDV serotypes 1 and 5–8 were circulating in Guangdong. In addition, EHDV prevalence always peaked in autumn, while eastern Guangdong had the highest EHDV seropositivity over the five-year period, displaying apparent temporal–spatial distribution of EHDV prevalence. A binary logistic model analysis indicated a significant association between cattle with BTV infections and seroprevalence of EHDV (OR = 1.70, p < 0.001). The co-infection of different serotypes of EHDV and BTV raises a high risk of potential genomic reassortment and is likely to pose a significant threat to cattle, thus urging more surveillance to monitor their circulating dynamics in China.

Epizootic hemorrhagic disease virus (EHDV) is a member of the genus Orbivirus, family Sedoreoviridae. It was firstly recognized in 1955 to cause a highly fatal disease of wild white-tailed deer in America. So far, EHDV was detected and isolated in many wild or domestic ruminants, and widely distributed all over the world. Although the domestic cattle and sheep infected by EHDV were usually asymptomatic or subclinical, several outbreaks of epizootic hemorrhagic disease (EHD) in deer and cattle had been reported. Many EHDV strains were isolated and sequenced in last two decades in China, which promoted a general serologic investigation of EHDV in China. In this study, 18,122 sera were collected from asymptomatic or subclinical domestic ruminants (cattle, cow, yaks, sheep, goats, and deer) in 116 regions belonging to 15 provinces in China. All the sera were tested by EHDV C-ELISA, and the results were obtained by big data analysis. EHDV infections were detected in the 14 of 15 provinces, and only Tibet (average altitude ≥ 4000 ​m) which was the highest province in China was free of EHDV. The numbers of seropositive collections in both bovine and goat/sheep were in an inverse proportion to the latitude. However, the seropositive rates in bovine were ranged from 0% to 100%, while the seropositive rates in goat/sheep were no more than 50%. The results suggested that bovine was obviously more susceptive for EHDV infection than goat and sheep, therefore might be a major reservoir of EHDV in China. The prevalence of EHDV was consistent with the distribution of Culicoides which were known as the sole insect vectors of EHDV. In particular, the seropositive rates of EHDV were very high in the southern provinces, which required the enhanced surveillance in the future.

Strain ZY190616^T was isolated from lung of a dead cow with hemorrhagic pneumonia in Yunnan Province, China. The strain was Gram-stain-negative, facultatively anaerobic bacterium. Phylogenetic analysis based on 16S rRNA gene sequence indicated that the strain was closely related to species of the genus Mannheimia and formed an independent clade with M.varigena CCUG 38462 ^T (97.0% similarity). Phylogenetic analysis based on recN gene indicated that the strain formed a clade with M.caviae CCUG 59995 ^T (87.8% similarity). Phylogenetic analysis based on rpoB gene indicated that the strain formed a clade with M.varigena CCUG 38462 ^T (94.7% similarity). The genomic OrthoANI values between strain ZY190616^T and M. ovis, M.haemolytica and M.granulomatis were 84.5%, 82.7% and 81.9%, respectively. The genomic G + C content was 39.8 mol%. The predominant fatty acids (> 5%) of the strain were C_16:0, C_14:0, C_18:1ω7c, summed feature 3 (C_16:1 ω7c and/ or C_16:1ω6c) and summed feature 2 (C14:0 3OH/ C16:1 Iso). The major polar lipids were phosphatidylglycerol (PG), phosphatidylethanolamine (PE), monophosphatidylglycerol (MGDG), triacylglycerol (TAG) and diphosphatidylglycerol (DLCL). The sole respiratory quinone was CoQ-7. Based on evidence from the taxonomic study, strain ZY190616^T represents a novel species of the genus Mannheimia, for which the name Mannheimia bovis sp. nov. is proposed. The type strain is ZY190616^T (= CCTCC AB 2020168 ^T = KCTC 25018 ^T).

The full-genome sequence of bluetongue virus serotype 15 (BTV-15) strain B105/YN/1996 isolated in China was determined for the first time. The virus was isolated from sentinel cattle in Yunnan Province, China, in 1996.

The full-genome sequence of the bluetongue virus serotype 1 (BTV-1) strain Y863, the first BTV-1 isolate of Eastern origin found in China, was determined. The virus was isolated from sheep during a severe outbreak of bluetongue in Shizhong County, Yunnan Province, southwest China, in 1979. The total size of the BTV-1 strain Y863 genome is 19,170 bp. Phylogenetic analyses demonstrate that it belongs to the major “Eastern” BTV topotype. The sequence information provided here will help in understanding the geographical origin and spread of this Chinese isolate of BTV-1, as well as aid in its comparison with global isolates of BTV-1 from sheep, cattle, and other host species origins.

The complete genomic sequence of a bluetongue virus serotype 4 (BTV-4) strain (strain YTS-4), isolated from sentinel cattle in Yunnan Province, China, is reported here. This work is the first to document the complete genomic sequence of a BTV-4 strain from China. The sequence information will help determine the geographic origin of Chinese BTV-4 and provide data to facilitate future analyses of the genetic diversity and phylogenetic relationships of BTV strains.