Large-Scale Comparative Analyses of Tick Genomes Elucidate Their Genetic Diversity and Vector Capacities.

Among arthropod vectors, ticks transmit the most diverse human and animal pathogens, leading to an increasing number of new challenges worldwide. Here we sequenced and assembled high-quality genomes of six ixodid tick species and further resequenced 678 tick specimens to understand three key aspects of ticks: genetic diversity, population structure, and pathogen distribution. We explored the genetic basis common to ticks, including heme and hemoglobin digestion, iron metabolism, and reactive oxygen species, and unveiled for the first time that genetic structure and pathogen composition in different tick species are mainly shaped by ecological and geographic factors. We further identified species-specific determinants associated with different host ranges, life cycles, and distributions. The findings of this study are an invaluable resource for research and control of ticks and tick-borne diseases.

Metavirome of 31 tick species provides a compendium of 1,801 RNA virus genomes.

The increasing prevalence and expanding distribution of tick-borne viruses globally have raised health concerns, but the full repertoire of the tick virome has not been assessed. We sequenced the meta-transcriptomes of 31 different tick species in the Ixodidae and Argasidae families from across mainland China, and identified 724 RNA viruses with distinctive virome compositions among genera. A total of 1,801 assembled and complete or nearly complete viral genomes revealed an extensive diversity of genome architectures of tick-associated viruses, highlighting ticks as a reservoir of RNA viruses. We examined the phylogenies of different virus families to investigate virome evolution and found that the most diverse tick-associated viruses are positive-strand RNA virus families that demonstrate more ancient divergence than other arboviruses. Tick-specific viruses are often associated with only a few tick species, whereas virus clades that can infect vertebrates are found in a wider range of tick species. We hypothesize that tick viruses can exhibit both 'specialist' and 'generalist' evolutionary trends. We hope that our virome dataset will enable much-needed research on vertebrate-pathogenic tick-associated viruses.

Genetic and hosts characterization of hantaviruses in port areas in Hainan Province, P. R. China.

BACKGROUND: Hantaviruses (HVs) are major zoonotic pathogens in China that cause hemorrhagic fever with renal syndrome (HFRS) posing a major threat to people's health. Hainan Province, an island located in Southeast China, is an ideal region for sea ports. The unique tropical monsoon climate in Hainan provides sufficient living conditions for rodents, which help spread HVs and other rodent-borne diseases. In the routine monitoring of hantavirus, there was no evidence that rodents in Hainan carried hantavirus. No patients infected with hantavirus were found in the past. However, the surveillance of HVs-carrying rodents covering the whole territory of Hainan has not stopped. METHODOLOGY/PRINCIPAL FINDINGS: For the monitoring of the prevalence of HVs in rodents and the search for theoretical reference for rodent control and HFRS prevention, a total of 60 rodents from 6 monitoring spots were trapped around main ports in Hainan between 2016 and 2019. HV positive samples were identified by a specific kit and sequenced. The data indicated that seven rodents (Rattus norvegicus) were positive for hantavirus with a positivity rate of 11.67%. Phylogenetic analysis suggested that the two complete sequence strains HN1 and HN4 in this research were highly similar to the sequence strains GZRn36 and GZRn148 isolated in Guangdong Province, and they located in the same phylogenetic tree branch which belongs to S2 subtype. Although the two partial sequences HT1 and HT2 isolated in Xisha Islands belong to S2 subtype according to the phylogenetic tree of L segment, they showed a great nucleotide difference with HN1 and HN4. We also found 13 amino acid variations compared with SEOV 80-39 and 6 amino acid mutations related to epitope, and the variations may reduce the effectiveness of the current HFRS vaccines used in humans. CONCLUSIONS/SIGNIFICANCE: The study indicated HVs carried by rodents found in Hainan Province may be transmitted from Guangdong Province through trading ports and carriage of goods by sea. So it is of great significance to strengthen the surveillance of rodents in port areas especially capture and eliminate rodents on ship. Timely elimination of host animals of hantavirus in port areas is necessary to prevent an outbreak of HVs disease.