Distribution of Dermacentor silvarum and Associated Pathogens: Meta-Analysis of Global Published Data and a Field Survey in China

Abstract

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.

The First Finding of Francisella tularensis subsp. mediasiatica in Krasnoyarsk Territory, Siberia, and an Update of the Subspecies Genetic Diversity

“…mediasiatica M.II were isolated from ixodid (hard) ticks, H. concinna and D. silvarum, in agreement with the known area of distribution of these two species of ticks [8,9]. Ixodid ticks, including H. concinna and D. silvarum, can parasitize birds, which could spread both the ticks themselves and the infectious agents, including F. tularensis [8][9][10][11]. H. concinna is the second most abundant tick species collected from birds [8].…”

The First Finding of <em>Francisella Tularensis</em> Subsp. <em>Mediasiatica</em> in Krasnoyarsk Territory, Siberia and an Update of the Subspecies Genetic Diversity

“…Accordingly, the area of distribution of these strains falls on the region of Russia in which the areas of distribution of these two species of ticks intersect [24,25]. Ixodid ticks including H. concinna and D. silvarum can parasitize birds, which could spread both the ticks themselves and the infectious agents, including F. tularensis [24][25][26]. H. concinna is the second most abundant tick species collected from birds [24].…”

Endogenous Viral Elements in Ixodid Tick Genomes

“…Assembled tick genomes were downloaded from the National Center for Biotechnology Information databases; when applicable, both RefSeq and GenBank assemblies were used (i.e., Dermacetor silvarum, Ixodes scapularis, and Rhipicephalus sanguineus; Table 1), as we have noted that EVE-encoding scaffolds may be removed from RefSeq during contaminant screening. The tick species in this analysis were selected primarily based on the availability of fully sequenced, assembled, and publicly available genomes, though all are relevant vectors of human disease [20][21][22][23][24] and/or significant ectoparasites on livestock [25,26] in different locations around the world. Putative EVE loci were identified as follows: first, all viral proteins were retrieved from the National Center for Biotechnology Information (NCBI) viral protein database (35.3 M sequences as of 30 May 30 2021) [30] and clustered using cd-hit [31] at a 95% amino acid identity level, resulting in 10.66 M representative sequences that were used in a TBLASTN query against the tick genome references (e-val = 1 × 10 −5 ).…”