Bao-Gui Jiang

Lyme spirochetes have coevolved with ticks to optimize transmission to hosts using tick salivary molecules (TSMs) to counteract host defenses. TSMs modulate various molecular events at the tick–host interface. Lymphotoxin-beta receptor (LTβR) is a vital immune receptor and plays protective roles in host immunity against microbial infections. We found that Ltbr knockout mice were more susceptible to Lyme disease spirochetes, suggesting the involvement of LTβR signaling in tick-borne Borrelia infection. Further investigation showed that a 15-kDa TSM protein from Ixodes persulcatus ( I. persulcatus salivary protein; IpSAP) functioned as an immunosuppressant to facilitate the transmission and infection of Lyme disease spirochetes. IpSAP directly interacts with LTβR to block its activation, thus inhibiting the downstream signaling and consequently suppressing immunity. IpSAP immunization provided mice with significant protection against I. persulcatus– mediated Borrelia garinii infection. Notably, the immunization showed considerable cross-protection against other Borrelia infections mediated by other ixodid ticks. One of the IpSAP homologs from other ixodid ticks showed similar effects on Lyme spirochete transmission. Together, our findings suggest that LTβR signaling plays an important role in blocking the transmission and pathogenesis of tick-borne Lyme disease spirochetes, and that IpSAP and its homologs are promising candidates for broad-spectrum vaccine development.

The geographic expansion of mosquitos is associated with a rising frequency of outbreaks of mosquito-borne diseases (MBD) worldwide. We collected occurrence locations and times of mosquito species, mosquito-borne arboviruses, and MBDs in the mainland of China in 1954−2020. We mapped the spatial distributions of mosquitoes and arboviruses at the county level, and we used machine learning algorithms to assess contributions of ecoclimatic, socioenvironmental, and biological factors to the spatial distributions of 26 predominant mosquito species and two MBDs associated with high disease burden. Altogether, 339 mosquito species and 35 arboviruses were mapped at the county level. Culex tritaeniorhynchus is found to harbor the highest variety of arboviruses (19 species), followed by Anopheles sinensis (11) and Culex pipiens quinquefasciatus (9). Temperature seasonality, annual precipitation, and mammalian richness were the three most important contributors to the spatial distributions of most of the 26 predominant mosquito species. The model-predicted suitable habitats are 60–664% larger in size than what have been observed, indicating the possibility of severe under-detection. The spatial distribution of major mosquito species in China is likely to be under-estimated by current field observations. More active surveillance is needed to investigate the mosquito species in specific areas where investigation is missing but model-predicted probability is high.

A novel Borrelia species, Candidatus Borrelia javanense, was found in ectoparasite ticks, Amblyomma javanense, from Manis javanica pangolins seized in anti-smuggling operations in southern China. Overall, 12 tick samples in 227 (overall prevalence 5.3%) were positive for Candidatus B. javanense, 9 (5.1%) in 176 males, and 3 (5.9%) in 51 females. The phylogenetic analysis, based on the 16S rRNA gene and the flagellin gene sequences of the Borrelia sp., exhibited strong evidence that Candidatus B. javanense did not belong to the Lyme disease Borrelia group and the relapsing fever Borrelia group but another lineage of Borrelia. The discovery of the novel Borrelia species suggests that A. javanense may be the transmit vector, and the M. javanica pangolins should be considered a possible origin reservoir in the natural circulation of these new pathogens. To our knowledge, this is the first identification of a novel Borrelia species agent in A. javanense from pangolins. Whether the novel agent is pathogenic to humans is unknown and needs further research.

Dermacentor silvarum is an obligate blood sucking arthropod and transmits various pathogens to humans and domestic animals. Recently several new viruses were detected in D. silvarum as an emerging disease threat. In this study, we aimed to analyze its geographical distribution and associated pathogens. Data were collected from multiple sources, including a field survey, reference book, and literature review. We searched various electronic databases with the terms “Dermacentor silvarum” OR “D. silvarum” for studies published since 1963 and the positive rates for Dermacentor silvarum-associated pathogens were estimated by meta-analysis. D. silvarum was found only in four countries in Eurasia, ranging from 22° N to 57° N latitude. At least 20 human pathogens were associated with D. silvarum, including five species of spotted fever group rickettsiae, three species in the family of Anaplasmataceae, three genospecies in the complex Borrelia burgdorferi sensu lato, Francisella tularensis, Babesia venatorum, Coxiella buenetii, Borrelia miyamotoi, and five species of virus. Among them, Rickettsia raoultii was widely detected in D. silvarum, showing the highest pooled positive rate (25.15%; 95% CI 13.31–39.27). Our work presents the most comprehensive data and analysis (to our knowledge) for the geographical distribution of D. silvarum and associated pathogens, revealing an emerging threat to public health and stocking farming. Continued surveillance and further investigations should be enhanced.

Background: Lyme disease is caused by Borrelia burgdorferis ensulato (BBSL) which is usually found in wild and domestic mammals worldwide. Human cases of B. burgdorferi infections have been identified in China, but little direct surveillance of potential rodent reservoirs has been performed in Yunnan Province, Southwestern China. Yunnan Province is a tropical area with a diverse topographic range and sustains a high biodiversity of small mammals that could potentially play an important role in the transmission of a variety of B. burgdorferi genospecies. Methods: 3659 small mammals were captured in 159 sample siteslocated 23 countries inYunnan Province and screened for BBSL infection by nested PCR based on 5S-23S rRNA intergenic spacer gene of BBSL.Univariate and multivariate forward stepwise logistic regression analysis was used to access the association between infections and related risk factors. Results: Infection with BBSL was confirmed in 3.99%(146/3659) of small mammals. Significant differences in prevalence rates of BBSL were observed at varying landscape types and altitudes.Small mammals in forested areas had higher prevalence rates than other landscape types as did small mammals found at altitudes greater than 2500 meters. The 5S-23S rRNA intergenic spacergene revealed that there were 5 genotype of BBSL, including B. afzelii, B. burgdorferisensustricto, B.japonica, B.gariniiand B.valaisiana , which demonstrate the genetic diversity and regional distribution. Conclusions: There exists a wide distribution and genetic diversity of endemic BBSL in Southwestern China, warranting further investigations and monitoring of clinical disease in individuals presenting with symptoms of Lyme disease in these areas. Author summary: Lyme disease is caused by Borrelia burgdorferi sensu lato (BBSL) which is usually found in wild and domestic mammals worldwide. Human cases of Borrelia burgdorferi sensu lato infections have been identified in China, but little direct surveillance of potential rodent reservoirs has been performed in Southwestern China. This study documents potential small mammal reservoir hosts collected from a large of sample sites from different landscape types and altitudes, with PCR and sequencing identifying the wide distribution and genetic diversity of endemic Borrelia burgdorferi sensu lato in Southwestern China. This was the first report that B. japonica was detected in Apodemus draco and Niviventer excelsior in China. This study adds to body of literature on Borrelia burgdorferi sensu lato in China. This work will provide insight regarding small mammals to target for surveillance and we access the association between gender, developmental stage of rodents, environmental landscape and altitude to better prevent human exposure.

The complete mitochondrial genome of Haemaphysalis concinna is reported for the first time in this study. Its entire mitogenome is 14,675 bp in length, contained 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and two non-coding regions. Among the 13 protein-coding genes, apart from the nad1, nad4, nad4L, and nad5 gene encoded on the L-strand, the remaining protein-coding genes were encoded on the H-strand. The phylogenetic analysis by Bayesian inference method shows that Amblyomma sphenodonti and H. parva formed one clade, while H. concinna and other species of genus Haemaphysalis formed the other clade, indicating that H. concinna belong to the genus Haemaphysalis.